* [PATCH v4 1/9] Add documentation for Sahara protocol.
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 2/9] bus: mhi: Move sahara protocol driver under drivers/bus/mhi Kishore Batta
` (7 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
Introduce documentation for the Sahara protocol, describing its
operational modes and their respective functions. The image transfer mode
enables firmware transfer from host to device. The memory debug mode
allows extraction of device memory contents to host. The command mode
facilitates retrieval of DDR training data from the device and also
to restore the training data back to device in subsequent boot of device
to save boot time.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
Documentation/sahara/index.rst | 14 +
Documentation/sahara/sahara_protocol.rst | 1241 ++++++++++++++++++++++++++++++
2 files changed, 1255 insertions(+)
diff --git a/Documentation/sahara/index.rst b/Documentation/sahara/index.rst
new file mode 100644
index 0000000000000000000000000000000000000000..073002c15a203344524e258b2aa0a6ce839e064b
--- /dev/null
+++ b/Documentation/sahara/index.rst
@@ -0,0 +1,14 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+========================
+Qualcomm Sahara protocol
+========================
+
+The Sahara protocol transfers data to and from memory and describes packet
+structures, packet flows, and their usage.
+
+.. toctree::
+ :maxdepth: 2
+ :caption: Contents
+
+ sahara_protocol
diff --git a/Documentation/sahara/sahara_protocol.rst b/Documentation/sahara/sahara_protocol.rst
new file mode 100644
index 0000000000000000000000000000000000000000..91204bb7d170be4fc4c85f142b8f0b93d3c421a0
--- /dev/null
+++ b/Documentation/sahara/sahara_protocol.rst
@@ -0,0 +1,1241 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+
+=============================
+Sahara protocol Specification
+=============================
+
+The Qualcomm Sahara protocol driver is primarily designed for transferring
+software images from a host device to a target device using a simplified data
+transfer mechanism over a link. However, the sahara protocol does not support
+any authentication/validation of the data sent between devices. Such a mechanism
+is beyond the scope of the protocol.
+
+The Sahara protocol defines two types of packets - Command packet and Data
+packet.
+
+Command packet
+--------------
+ These packets are sent between the host and the target to setup transfers of
+ data packets. The command packets contain a command ID and packet length.
+ Depending on the command, the packet may contain additional command specific
+ field.
+
++-------------+---------------+----------------+----------------+
+| Command ID | Packet length | Optional field | Optional field |
++-------------+---------------+----------------+----------------+
+
+Data packet
+-----------
+ The data packets contain RAW data as shown below.
+
++---------------------------------------------------------+
+| RAW Data (arbitrary number of bytes) |
++---------------------------------------------------------+
+
+Command packet optional fields
+------------------------------
+
++---------+---------------+---------+-----------------------------------------+
+| ID val | Field | Sent by | Description |
++---------+---------------+---------+-----------------------------------------+
+| 0x0 | - | - | Invalid |
++---------+---------------+---------+-----------------------------------------+
+| 0x1 | Hello packet | Target | Initializes connection and protocol |
++---------+---------------+---------+-----------------------------------------+
+| 0x2 | Hello response| Host | Acknowledges connection and protocol |
+| | | | sent by target. Also used to set mode of|
+| | | | operation for target to execute. |
++---------+---------------+---------+-----------------------------------------+
+| 0x3 | Read data | Target | Reads specified number of bytes from |
+| | | | host for a given image. |
++---------+---------------+---------+-----------------------------------------+
+| 0x4 | End of image | Target | Indicates host that the single image tx |
+| | transfer | | is complete. Also used to indicate a |
+| | | | target failure during an image transfer |
++---------+---------------+---------+-----------------------------------------+
+| 0x5 | Done packet | Host | Sends acknowledgment from host that a |
+| | | | single image transfer is complete. |
++---------+---------------+---------+-----------------------------------------+
+| 0x6 | Done response | Target | Provides the following information to |
+| | | | host. |
+| | | | 1. Target is exiting protocol |
+| | | | 2. Whether the target expects to |
+| | | | re-enter protocol to transfer another |
+| | | | image. |
++---------+---------------+---------+-----------------------------------------+
+| 0x7 | Reset packet | Host | Instructs target to perform a reset. |
++---------+---------------+---------+-----------------------------------------+
+| 0x8 | Reset response| Target | Indicates host that target is about to |
+| | | | reset. |
++---------+---------------+---------+-----------------------------------------+
+| 0x9 | Memory debug | Target | Indicates host that target has entered |
+| | packet | | a debug mode where it is ready to |
+| | | | transfer its system memory contents |
++---------+---------------+---------+-----------------------------------------+
+| 0xA | Memory read | Host | Reads specified number of bytes from |
+| | packet | | target's system memory, starting from a |
+| | | | specified address. |
++---------+---------------+---------+-----------------------------------------+
+| 0xB | Command ready | Target | Indicates host that target is ready to |
+| | packet | | receive client commands. |
++---------+---------------+---------+-----------------------------------------+
+| 0xC | Command switch| Host | Indicates target to switch modes. |
+| | mode packet | | 1. Image transfer pending mode. |
+| | | | 2. Image transfer complete mode. |
+| | | | 3. Memory debug mode. |
+| | | | 4. Command mode. |
++---------+---------------+---------+-----------------------------------------+
+| 0xD | Command | Host | Indicates target to execute a given |
+| | execute packet| | client command. |
++---------+---------------+---------+-----------------------------------------+
+| 0xE | Command | Target | Indicates host that target has executed |
+| | execute | | client command. Also used to indicate |
+| | response | | status of executed command. |
+| | packet | | |
++---------+---------------+---------+-----------------------------------------+
+| 0xF | Command | Host | Indicates target that host is ready to |
+| | execute | | receive data resulting from executing |
+| | data | | previous client command. |
+| | packet | | |
++---------+---------------+---------+-----------------------------------------+
+| 0x10 | 64 bit Memory | Target | Indicates host that target has entered |
+| | debug packet | | a debug mode where it is ready to |
+| | | | transfer its 64 bit system memory |
+| | | | contents. |
++---------+---------------+---------+-----------------------------------------+
+| 0x11 | 64 bit Memory | Host | Reads specified number of bytes from |
+| | read packet | | target's system memory, starting from a |
+| | | | 64 bit specified address. |
++---------+---------------+---------+-----------------------------------------+
+| 0x12 | 64 bit Read | Target | Reads specified number of bytes from |
+| | data | | host for a given 64 bit image. |
++---------+---------------+---------+-----------------------------------------+
+| 0x13 | Reset sahara | Host | Resets Sahara state machine and enters |
+| | sate machine | | Sahara entry without target reset |
+| | packet | | |
++---------+---------------+---------+-----------------------------------------+
+| 0x14 | Write data | Target | Writes specified number of bytes to host|
+| | packet | | for a given image |
++---------+---------------+---------+-----------------------------------------+
+| Others | - | - | Invalid |
++---------+---------------+---------+-----------------------------------------+
+
+
+Hello Packet
+------------
+
+The hello packet is the first packet that the target sends to the host. If the
+host receives any other packet, it sends a reset command to the target. When the
+host receives a valid hello packet, it first verifies that the protocol running
+on the target is compatible with the protocol running on the host. If the
+protocol mismatch, the host sends a reset command to the target. The target uses
+the following format while sending a hello packet.
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Version | 4 | Version number of this protocol |
++-----------+-------------+--------------------------------------+
+| Version | 4 | Lowest Compatible version |
+| Compatible| | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Maximum command packet length |
+| packet | | (in bytes) the protocol supports. |
+| length | | |
++-----------+-------------+--------------------------------------+
+| Mode | 4 | Expected mode of target operation |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use. |
++-----------+-------------+--------------------------------------+
+
+The target also sends the following information:
+ 1. Maximum length of the command packet that it supports. The host uses this
+ information to avoid sending more bytes than the target can support in the
+ receiving command buffer.
+ 2. Mode of operation it expects to enter, based on the boot up sequence. The
+ supported modes of operation for the target are as follows:
+
++-----------------------------+---------+------------------------------------+
+| Mode | Mode ID | Description |
++-----------------------------+---------+------------------------------------+
+| SAHARA_MODE_IMAGE_TX_PENDING| 0x0 | Image transfer is in the pending |
+| | | mode. Transfer image from the host.|
+| | | After completion, the host should |
+| | | expect another image transfer |
+| | | request. |
++-----------------------------+---------+------------------------------------+
+|SAHARA_MODE_IMAGE_TX_COMPLETE| 0x1 | Image transfer is in the complete |
+| | | mode. Transfer image from the host.|
+| | | After completion, the host should |
+| | | not expect another image transfer |
+| | | request. |
++-----------------------------+---------+------------------------------------+
+| SAHARA_MODE_MEMORY_DBEUG | 0x2 | Memory debug mode. The host should |
+| | | prepare to receive a memory dump |
+| | | from the target. |
++-----------------------------+---------+------------------------------------+
+| SAHARA_MODE_COMMAND | 0x3 | Command mode. The host executes |
+| | | operations on the target by sending|
+| | | the appropriate client command to |
+| | | the sahara client running on the |
+| | | target. The Sahar client interprets|
+| | | the client command and the response|
+| | | is sent after execution of the |
+| | | given command. |
++-----------------------------+---------+------------------------------------+
+
+Hello response packet
+---------------------
+
+After the host validates the protocol running on the target, it sends a response
+to the target. The response contains the following information.
+1. The protocol version that is running.
+2. The minimum protocol version that it supports.
+3. The mode of operation.
+
+The host sets the packet status field to success if no errors occur on the host
+side. After the target receives this packet, it can proceed with data transfer
+requests or memory debug. The host uses the following format while sending a
+hello response packet.
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++===========+=============+======================================+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet (in bytes) |
++-----------+-------------+--------------------------------------+
+| Version | 4 | Version number of this protocol |
++-----------+-------------+--------------------------------------+
+| Compatible| 4 | Lowest Compatible version |
++-----------+-------------+--------------------------------------+
+| Status | 4 | Success or error code |
++-----------+-------------+--------------------------------------+
+| Mode | 4 | Mode of operation for target to |
+| | | execute |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+| Reserved | 4 | Reserved for future use |
++-----------+-------------+--------------------------------------+
+
+
+Read data packet / 64 bit read data packet
+------------------------------------------
+
+The read data packet serves as a generic data transfer packet when any image
+data is to be transferred from the host to the target. This packet allows
+flexibility in the way that the image is transferred from the host to the
+target. As the target controls which data gets transferred, the target can
+determine what parts of the image get transferred and in what order. The host
+need not be familiar about the structure of the image. It must open the file and
+start transferring the data to the target based on the parameters specified in
+the packet.
+
+This gives the target complete control over how the images are transferred and
+processed. To initiate an image transfer, the target fills the read data packet
+with the image ID corresponding to the image that it wants to receive. The
+target also sends the offset into the image file and the length of the data(in
+bytes) it wants to read from the image. After the host receives this packet, the
+host responds with a data packet, which contains image data with the length
+specified in the read data packet. The host uses the following format while
+transferring the read data packet and 64-bit read data packet.
+
+
+Read data packet format
+=======================
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Image ID | 4 | ID of the image to be transferred. |
++-----------+-------------+--------------------------------------+
+| Data | 4 | Offset into the image file to start |
+| offset | | transferring data. |
++-----------+-------------+--------------------------------------+
+| Data | 4 | Number of bytes target wants to |
+| Length | | transfer from the image. |
++-----------+-------------+--------------------------------------+
+
+
+64-bit read data packet format
+==============================
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Image ID | 8 | ID of the image to be transferred. |
++-----------+-------------+--------------------------------------+
+| Data | 8 | Offset into the image file to start |
+| offset | | transferring data. |
++-----------+-------------+--------------------------------------+
+| Data | 8 | Number of bytes target wants to |
+| Length | | transfer from the image. |
++-----------+-------------+--------------------------------------+
+
+If any of the preceding fields are invalid, or if any other error occurs on the
+host, the host sends a data packet with length that does not match with what the
+target was expecting. The resulting error forces the target to send an end of
+image transfer packet with an error code in the status field and enables both
+the target and the host to enter an error handling state.
+
+End of Image transfer packet
+----------------------------
+
+If an image transfer is successfully completed, the target sends the host an end
+of image transfer packet with a success status. The target then waits for the
+host to send a done packet. If any error occurs during the transfer or
+processing of the image data, the status is set to the corresponding error code,
+and the target waits for a different command packet.
+
+The host uses the following format while transferring end of image transfer
+packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Image ID | 4 | ID of the image that was being |
+| | | transferred. |
++-----------+-------------+--------------------------------------+
+| Status | 4 | Success or error code |
++-----------+-------------+--------------------------------------+
+
+Done packet
+-----------
+
+If the host receives an end of image transfer packet with a success status, the
+host sends a done packet to indicate the target that it can exit the protocol
+and continue execution of code. The host uses the following format while sending
+the done packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+
+To transfer another image from the host, the target must re-initiate the
+protocol by starting with another hello packet.
+
+Done Response packet
+--------------------
+
+If the target receives a done packet, it responds with a done response packet
+containing the image transfer status. The target uses the following format while
+sending the done response packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Image Tx | 4 | Indicates whether target is |
+| Status | | expecting to receive another image |
+| | | or not. |
++-----------+-------------+--------------------------------------+
+
+If all the images are transferred, the target sends a complete status to enable
+the host to exit the protocol. If all the images are not transferred, the target
+sends a pending status and waits for another hello packet to arrive.
+
+Reset Packet
+------------
+
+The host sends a reset packet to reset the target. The target services a reset
+request only if its in a state where reset requests are valid. If the target
+receives an invalid reset request, the target sends an error in an end of image
+transfer packet. The format of reset packet is as follows:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+
+
+Reset response packet
+---------------------
+
+If the target receives a valid reset request, it sends a reset response packet
+just before it resets. The purpose of this response is to acknowledge the host
+that the target received the reset request. The format of reset response packet
+is as follows:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+
+
+Memory debug packet
+-------------------
+
+The target initiates a memory dump by sending the host a memory debug packet.
+This packet contains the address and length of the memory debug table. The
+memory debug table is a listing of memory locations that can be accessed and
+dumped to the host. The target uses the following format while sending the
+memory debug packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Memory | 4 | Target sets this field to the address|
+| table | | in memory that stores the memory |
+| Address | | debug table. |
++-----------+-------------+--------------------------------------+
+| Memory | 4 | Length in bytes of memory debug |
+| table | | table. |
+| Length | | |
++-----------+-------------+--------------------------------------+
+
+Given the memory table address and length, the host issues a memory read to
+retrieve the table. After the host receives the memory table information, it can
+decode each entry and issue memory read requests to dump each memory location.
+
+Memory read packet / 64-bit memory read packet
+----------------------------------------------
+
+The host issues memory read commands for each section of memory that it dumps.
+The host uses the following format while sending the memory read packet and 64
+bit memory read packet:
+
+Memory read packet format
+=========================
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Memory | 4 | Memory location to read. |
+| Address | | |
++-----------+-------------+--------------------------------------+
+| Memory | 4 | Length in bytes of memory to read |
+| Length | | |
++-----------+-------------+--------------------------------------+
+
+64 bit memory read packet format
+================================
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Memory | 8 | Memory location to read. |
+| Address | | |
++-----------+-------------+--------------------------------------+
+| Memory | 8 | Length in bytes of memory to read |
+| Length | | |
++-----------+-------------+--------------------------------------+
+
+The accessible regions are defined in the memory debug table. For each memory
+read command received, the target verifies that the specified memory(address and
+length) is accessible and responds with a raw data packet. The content and
+length of the raw data packet is the memory dump starting from the memory
+address and length specified in the memory read packet. The memory debug table
+can also be read using a memory read command by setting the address and length
+to the values specified in the memory debug packet.
+
+If any error occurs on the target, an end of image transfer packet is sent with
+the corresponding error code and the host recognizes whether it is actual memory
+data or an end of image transfer packet. The host issues a reset command on
+completion of a successful memory dump. However, the protocol does not force
+this implementation.
+
+Command ready packet
+--------------------
+
+The target sends this packet to the host to indicate that the target is ready to
+execute client commands. The target uses the following format while sending the
+command ready packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+
+
+Command switch mode packet
+--------------------------
+
+The host sends the command switch mode packet to the target so that the target
+can switch to another mode. The host uses the following format while sending the
+command switch mode packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Mode | 4 | Mode of operation for target |
+| | | to execute. |
++-----------+-------------+--------------------------------------+
+
+Command execute packet
+----------------------
+
+The host sends this packet to execute the given client command on the target. If
+the client command successfully executes, the target sends a command execute
+response packet. If an error occurs, the target sends an end of image transfer
+packet with the corresponding error code. The host uses the following format
+while sending command execute packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Client | 4 | Client Command to be executed. |
+| Command | | |
++-----------+-------------+--------------------------------------+
+
+
+Client commands
+===============
+
++------------+-------------+--------------------------------------+
+| Client ID | Length | Description |
++------------+-------------+--------------------------------------+
+| 0x8 | 4 | Get Command ID list. |
++------------+-------------+--------------------------------------+
+| 0x9 | 4 | Get DDR training data. |
++------------+-------------+--------------------------------------+
+
+Command execute Response packet
+-------------------------------
+
+The target sends this packet if it successfully executes the client command. The
+target uses the following format while sending the command execute response
+packet.
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Client | 4 | Client Command to be executed. |
+| Command | | |
++-----------+-------------+--------------------------------------+
+| Response | 4 | Number of bytes for response data. |
+| Length | | |
++-----------+-------------+--------------------------------------+
+
+Command execute data packet
+---------------------------
+
+The host sends this packet if the response length received in the command
+execute response packet is greater than 0. The host uses the following format
+while sending command execute data packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Client | 4 | Client Command executed. |
+| Command | | |
++-----------+-------------+--------------------------------------+
+
+The packet indicates the target to send the response data in a raw data packet.
+The target sends the response data upon receiving this packet.
+
+64-bit memory debug packet
+--------------------------
+
+The target sends this packet to the host to initiate a memory dump. The packet
+contains 64-bit address and length of the memory table. The target uses the
+following format while sending 64-bit memory debug packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Memory | 8 | Target sets this field to the 64-bit |
+| table | | address in memory that stores the |
+| Address | | memory debug table. |
++-----------+-------------+--------------------------------------+
+| Memory | 8 | Length in bytes of memory debug |
+| table | | table. |
+| Length | | |
++-----------+-------------+--------------------------------------+
+
+Reset Sahara state machine packet
+---------------------------------
+
+The host sends a reset sahara state machine packet whenever it wants to reset
+Sahara state machine. When the target receives a reset sahara state machine
+request, it reinitializes sahara protocol and sends the hello packet to the
+host. The sahara protocol is restarted without a target reset. The host uses the
+following format while sending the reset sahara state machine packet:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+
+Write data packet
+-----------------
+
+Write data packet serves as a generic data transfer packet when any data is
+transferred from the target to the host. This packet allows flexible data
+transfer from the target to the host.
+
+As the target controls what data gets transferred, target can determine what
+parts of the data get transferred and in what order. The host does not need to
+know anything about the structure of the data. It only needs to open the file
+and start accepting the data to the host based on the parameters specified in
+the packet.
+
+To initiate a write data transfer, the target fills the write data packet with
+the image ID corresponding to the image data that it wants to send. The target
+also sends the offset into the output file and the length of the data(in bytes)
+it wants to write from the target. As soon as the host receives the packet, the
+host opens an output file and waits to receive the data packets. After the
+packet is received, the content from the data pcket is written to the output
+file, The format of the write data packet is as follows:
+
++-----------+-------------+--------------------------------------+
+| Field | Length | Description |
+| | (bytes) | |
++-----------+-------------+--------------------------------------+
+| Command | 4 | Command identifier code |
++-----------+-------------+--------------------------------------+
+| Length | 4 | Length of the packet(in bytes) |
++-----------+-------------+--------------------------------------+
+| Data | 8 | Offset into the image file to start |
+| offset | | writing the data to host. |
++-----------+-------------+--------------------------------------+
+| Image ID | 4 | ID of the image to be transferred. |
++-----------+-------------+--------------------------------------+
+| Data | 4 | Number of bytes target wants to |
+| Length | | transfer the data to the host. |
++-----------+-------------+--------------------------------------+
+
+
+Command packet flow between host and target
+-------------------------------------------
+
+Packet flow is a process of exchange of information as packets between the host
+and the target in a specific way using command packets. The sahara protocol
+allows packet processing for the following scenarios:
+
+1. Transferring an image from the host to the target.
+2. Dumping memory from the target to the host.
+3. Loading DDR calibration data on flashless target.
+
+Packet flow for Image transfer
+------------------------------
+
+The packet flow is performed between the host and target for a successful image
+transfer.
+
+.. code-block:: text
+
+ Host Target
+ | HELLO |
+ | (mode = image transfer) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = image transfer) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID, 0, offset, |
+ | size of image header) |
+ |<--------------------------|
+ | |
+ | RAW_DATA |
+ | (size of image header) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID, segment 0 offset,|
+ | size of segment 0) |
+ |<--------------------------|
+ | RAW_DATA |
+ | (size of segment 0) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID, segment 1 offset,|
+ | size of segment 1) |
+ |<--------------------------|
+ | |
+ | |
+ | RAW_DATA |
+ | (size of segment 1) |
+ |-------------------------->|
+ | ... |
+ | ... |
+ | ... |
+ | ... |
+ | |
+ | |
+ | READ_DATA |
+ | (img ID, segment N offset,|
+ | size of segment N) |
+ |<--------------------------|
+ | |
+ | |
+ | |
+ | RAW_DATA |
+ | (size of segment N) |
+ |-------------------------->|
+ | |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ |<--------------------------|
+ | |
+
+The packet flow sequence for image transfer is as follows:
+
+1. A hello packet is sent from the target to the host to initiate the protocol
+ with the mode set to either image transfer pending or image transfer
+ complete (depending on the target's boot sequence).
+
+2. The host sends a hello response packet with a success status and sets the
+ mode to the mode received in the hello packet. After it receives the hello
+ packet and validates the protocol version running on the target.
+
+3. After the target receives the hello response, the target initiates the
+ image transfer request by sending read data packets. Each read data packet
+ specifies the image that the target wishes to receive and what part of the
+ image is to be transferred.
+
+4. During normal operation, the target first requests image header information.
+
+ a. The image header information specifies image size and location of the
+ image data that is to be transferred.
+
+ b. The image header information (which is sent as a read data request)
+ allows the target to know the format of the image to be transferred.
+ The protocol does not require the host to know anything about the
+ image formats and allows the host to read and transfer data from the
+ image as requested by the target.
+
+ c. If the image is a standalone binary image without any data segmentation
+ (which means the data is entirely contiguous when stored as well as
+ transferred to the target system memory), then the target requests for
+ entire image data to be sent in one transfer.
+
+ d. If the image data is segmented and requires scattering of the data
+ segments to noncontiguous system memory locations, the target issues
+ multiple read data requests to enable each data segment to be
+ transferred directly to the respective destination address. This
+ scattered information resides in the image header and is parsed by the
+ target before issuing the read data requests.
+
+5. After receiving a read data request, the host parses the image ID, data
+ offset, and data length to transfer data from the corresponding image file.
+ The host sends the requested data without any packet header.
+
+6. The target directly transfers the data to the destination address without
+ any software processing or temporarily buffering of the data in system
+ memory by transferring the image header to the targert and setting the
+ receive buffer for the data as the destination address in system memory.
+
+7. After the target successfully receives all segments for an image, the
+ target sends an end of image transfer packet with the image ID of the
+ corresponding image, and a success status. The host stops reading and
+ closes the image file after receiving the success status.
+
+8. The host sends a done packet to allow the target to exit the protocol after
+ it receives a successgul end of image transfer packet.
+
+9. After the target receives the done packet, the target sends a done response
+ packet to the host. This packet indicates if the target expects another
+ image to be transferred and if the host can continue to run the protocol.
+
+Packet flow for memory debug
+----------------------------
+
+The packet flow is performed between the host and the target for the successful
+memory debug.
+
+.. code-block:: text
+
+ Host Target
+ | HELLO |
+ | (mode = memory debug) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = memory debug) |
+ |-------------------------->|
+ | |
+ | MEMORY_DEBUG |
+ | (location of mem table, |
+ | size of memory table) |
+ |<--------------------------|
+ | |
+ | MEMORY_READ |
+ | (Address from region 0 ,|
+ | size of region 0) |
+ |-------------------------->|
+ | RAW_DATA |
+ | (size of region 0) |
+ |<--------------------------|
+ | |
+ | MEMORY_READ |
+ | (Address from region 1 ,|
+ | size of region 1) |
+ |-------------------------->|
+ | RAW_DATA |
+ | (size of region 1) |
+ |<--------------------------|
+ | MEMORY_READ |
+ | (Address from region 2 ,|
+ | size of region 0) |
+ |-------------------------->|
+ | RAW_DATA |
+ | (size of region 2) |
+ |<--------------------------|
+ | ... |
+ | ... |
+ | ... |
+ | ... |
+ | |
+ | MEMORY_READ |
+ | (Address from region N ,|
+ | size of region N) |
+ |-------------------------->|
+ | RAW_DATA |
+ | (size of region N) |
+ |<--------------------------|
+ | |
+ | RESET |
+ |-------------------------->|
+ | |
+ | |
+ | RESET_RESP |
+ |<--------------------------|
+ | |
+
+The packet flow sequence for image transfer is as follows:
+
+1. A hello packet is sent from the target to the host to initiate the protocol
+ with mode set to memory debug.
+
+2. The host sends a hello response packet with a success status and sets the
+ mode to memory debug after it receives the hello packet and validates the
+ protocol version running on the target.
+
+3. After the target receives the hello response, the target initiates the
+ memory dump by sending a memory debug packet with the location and size of
+ the memory debug table. The memory debug table specifies accessible memory
+ regions.
+
+4. The host then initiates a memory read packet to read the memory debug
+ table and receives the table in a raw data packet after it receives the
+ memory debug packet.
+
+5. The host then decodes the table and issues memory reads for each accessible
+ region. The data for each region is sent in a raw data packet.
+
+6. Upon completion, the host issues a reset to the target. The target sends a
+ reset response and resets the target.
+
+7. The host can alternatively send a command switch mode packet to allow the
+ target to switch modes and avoid a reset.
+
+
+Packet flow to load DDR calibration data on target
+--------------------------------------------------
+
+The packet flow is performed between the host and the target to load DDR
+calibration data on flashless target. This packet flow is initiated when the
+device boots up for the first time and needs DDR calibration. This packet flow
+is also initiated in other scenarios, such as build update or any reason for
+which DDR calibration data gets corrupted.
+
+First boot scenario or invalid calibration data in filesystem.
+--------------------------------------------------------------
+
+.. code-block:: text
+
+ Host Target
+ | HELLO |
+ | (mode = image transfer) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = image transfer) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID:34, 0, offset, |
+ | size of DDR training data)|
+ |<--------------------------|
+ | |
+ | RAW_DATA |
+ |(size of DDR training data)|
+ |-------------------------->|
+ | |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ |1. First boot scenario. |
+ | DDR driver performs |
+ | calibration and returns |
+ | to SBL. |
+ |2. Next: Push DDR |
+ | Calibration data to host |
+ | |
+ | |
+ | HELLO |
+ | (mode = COMMAND mode) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = COMMAND mode ) |
+ |-------------------------->|
+ | |
+ | CMD_READY |
+ |<--------------------------|
+ | |
+ | CMD_EXEC |
+ |(cmd id = 8, Get command |
+ | ID to be executed) |
+ |-------------------------->|
+ | |
+ | CMD_EXEC_RESP |
+ |(cmd id: 8, resp len = 4) |
+ |<--------------------------|
+ | |
+ | CMD_EXEC_GET_DATA |
+ | (ID = 0x8) |
+ |-------------------------->|
+ | |
+ | RAW_DATA |
+ | (0x00000009) |
+ |<--------------------------|
+ | |
+ | CMD_EXEC |
+ | (cmd id: 9, resp len > 0) |
+ |-------------------------->|
+ | |
+ | |
+ | CMD_EXEC_RESP |
+ |(cmd id: 9, resp len > 0) |
+ |<--------------------------|
+ | |
+ | CMD_EXEC_GET_DATA |
+ | (ID = 0x9) |
+ |-------------------------->|
+ | |
+ | RAW_DATA |
+ | (valid training data) |
+ |<--------------------------|
+ | |
+ |3. Host sends switch to |
+ |image tx mode to continue |
+ |booting. |
+ | |
+ | |
+ | CMD_SWITCH_MODE |
+ | (mode = IMAGE_TX_PENDING) |
+ |-------------------------->|
+ | |
+ | |
+ | HELLO |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |-------------------------->|
+ | |
+ |4. Boot/Load rest of the |
+ | images.... |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ |(mode = IMAGE_TX_COMPLETE) |
+ |<--------------------------|
+ | |
+
+The packet flow sequence is as follows :
+
+1. The target sends the hello packet to the host to initiate the protocol
+ with the mode set to image transfer pending.
+
+2. The host sends a hello response packet with a success status and sets the
+ mode to image transfer pending after it receives the hello packet and
+ validates the protocol version running on the target.
+
+3. After the target receives the hello response, it initiates the data
+ transfer by requesting the size of DDR training/calibration data.
+
+4. The host sends back the DDR training/calibration data to the target.
+
+5. The target decodes the training data and does not find valid DDR
+ calibration data, target sends END_IMAGE_TX to interrupt the transfer.
+
+6. The host sends DONE after receives END_IMAGE_TX.
+
+7. The target sends DONE_RESP with mode = IMAGE_TX_PENDING because it has
+ not received all images.
+
+8. The target executes DDR training process to generate valid DDR calibration
+ data and prepares to push back to host.
+
+9. The target initiates protocol by sending a hello packet with COMMAND_MODE
+ to the host.
+
+10. The host sends a hello response packet with a success status and sets the
+ mode to COMMAND_MODE.
+
+11. The target sends CMD_READY to the host.
+
+12. The host receives CMD_READY and starts to get command IDs to be executed.
+
+13. The target sends CMD_ID = 9 to push DDR calibration data to host.
+
+14. The host executes CMD_ID = 9 to get DDR calibration data from the target.
+
+15. The target sends RAW_DATA with the payload which contains DDR calibration
+ data to host.
+
+16. The host saves training data in the kernel buffer and exposes to userspace
+ via the sysfs entry. The host sends CMD_SWITCH_MODE with the mode set to
+ IMAGE_TX_PENDING to continue booting.
+
+17. After the target receives the CMD_SWITCH_MODE command, it sends HELLO to
+ the host with the mode set to IMAGE_TX_PENDING. The target and the host
+ repeat the packet flow for image transfer to get all booting-required
+ images.
+
+18. Upon successful transfer of all images, the target sends an END_IMAGE_TX
+ packet with a success status to the host.
+
+19. The host sends DONE after it receives END_IMAGE_TX.
+
+20. The target sends DONE_RESP with the mode set to IMAGE_TX_COMPLETE because
+ it has received all images. The process has been completed after the host
+ receives DONE_RESP with the mode set to IMAGE_TX_COMPLETE.
+
+Subsequent boot scenario with valid DDR calibration data
+--------------------------------------------------------
+
+The below firgure shows the subsequent boot scenario with valid DDR calibration
+data process being loaded from host to target.
+
+.. code-block:: text
+
+ Host Target
+ | HELLO |
+ | (mode = image transfer) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = image transfer) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID:34, 0, offset, |
+ | size of DDR training data)|
+ |<--------------------------|
+ | |
+ | RAW_DATA |
+ |(size of DDR training data)|
+ |-------------------------->|
+ | |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ | |
+ | Subsequent boot scenario |
+ | (valid calibration data) |
+ | DDR driver configures DDR |
+ | using valid calibration |
+ | data |
+ | |
+ | |
+ | HELLO |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |-------------------------->|
+ | |
+ | Boot/Load rest of the |
+ | images.... |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ |(mode = IMAGE_TX_COMPLETE) |
+ |<--------------------------|
+ | |
+
+The packet flow is as follows :
+
+1. The target sends the hello packet to the host to initiate the protocol
+ with the mode set to image transfer pending.
+
+2. The host sends a hello response packet with a success status and sets the
+ mode to image transfer pending after it receives the hello packet and
+ validates the protocol version running on the target.
+
+3. After the target receives the hello response, it initiates the images
+ transfer by requesting the training/calibration data from the host.
+
+4. The host sends back the DDR training/calibration data to the target.
+
+5. The target decodes the DDR training/calibration data and finds valid DDR
+ calibration data.
+
+6. The host sends RAW_DATA with the size of the DDR calibration data to the
+ target.
+
+7. Upon successful transfer of DDR calibration data, the target sends an
+ END_IMAGE_TX packet with a success status.
+
+8. The host sends DONE after it receives END_IMAGE_TX.
+
+9. The target sends DONE_RESP with mode = IMAGE_TX_PENDING because it has not
+ received all images.
+
+10. The target continues booting with valid DDR calibration data.
+
+11. The target and the host repeat the packet flow for image transfer to get
+ all booting-required images.
+
+12. After successful transfer of all images, the target sends an END_IMAGE_TX
+ packet with a success status to the host.
+
+13. The host sends DONE after it receives END_IMAGE_TX.
+
+14. The target sends DONE_RESP with the mode set to IMAGE_TX_COMPLETE because
+ it has received all images. The process has been completed after the host
+ receives DONE_RESP with the mode set to IMAGE_TX_COMPLETE.
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 2/9] bus: mhi: Move sahara protocol driver under drivers/bus/mhi
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
2026-03-19 6:31 ` [PATCH v4 1/9] Add documentation for Sahara protocol Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 3/9] bus: mhi: Match devices exposing the protocol on the SAHARA channel Kishore Batta
` (6 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
The Sahara protocol driver is currently located under the QAIC
accelerator subsystem even though protocol itself is transported over the
MHI bus and is used by multiple Qualcomm flashless devices.
Relocate the Sahara protocol driver to drivers/bus/mhi and register it as
an independent MHI protocol driver. This avoids treating Sahara as QAIC
specific and makes it available for reuse by other MHI based devices.
As part of this move, introduce a dedicated Kconfig and Makefile under the
MHI subsystem and expose the sahara interface via a common header.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/accel/qaic/Kconfig | 1 +
drivers/accel/qaic/Makefile | 3 +--
drivers/accel/qaic/qaic_drv.c | 11 ++---------
drivers/bus/mhi/Kconfig | 1 +
drivers/bus/mhi/Makefile | 3 +++
drivers/bus/mhi/sahara/Kconfig | 18 ++++++++++++++++++
drivers/bus/mhi/sahara/Makefile | 2 ++
drivers/{accel/qaic => bus/mhi/sahara}/sahara.c | 16 +++++++++++-----
{drivers/accel/qaic => include/linux}/sahara.h | 0
9 files changed, 39 insertions(+), 16 deletions(-)
diff --git a/drivers/accel/qaic/Kconfig b/drivers/accel/qaic/Kconfig
index 116e42d152ca885b8c59e33c7a87519a0abc6bb3..1e5f1f4fa93c12d8ca8fb37633f2f0bee9997499 100644
--- a/drivers/accel/qaic/Kconfig
+++ b/drivers/accel/qaic/Kconfig
@@ -8,6 +8,7 @@ config DRM_ACCEL_QAIC
depends on DRM_ACCEL
depends on PCI && HAS_IOMEM
depends on MHI_BUS
+ select MHI_SAHARA
select CRC32
select WANT_DEV_COREDUMP
help
diff --git a/drivers/accel/qaic/Makefile b/drivers/accel/qaic/Makefile
index 71f727b74da3bb4478324689f02a7cea24a05c2d..e7b8458800072aa627f7f36c3257883aa56f4ce4 100644
--- a/drivers/accel/qaic/Makefile
+++ b/drivers/accel/qaic/Makefile
@@ -13,7 +13,6 @@ qaic-y := \
qaic_ras.o \
qaic_ssr.o \
qaic_sysfs.o \
- qaic_timesync.o \
- sahara.o
+ qaic_timesync.o
qaic-$(CONFIG_DEBUG_FS) += qaic_debugfs.o
diff --git a/drivers/accel/qaic/qaic_drv.c b/drivers/accel/qaic/qaic_drv.c
index 63fb8c7b4abcbe4f1b76c32106f4e8b9ea5e2c8e..76cc8086825e7949ed756d51fcb56a08f392d228 100644
--- a/drivers/accel/qaic/qaic_drv.c
+++ b/drivers/accel/qaic/qaic_drv.c
@@ -15,6 +15,7 @@
#include <linux/msi.h>
#include <linux/mutex.h>
#include <linux/pci.h>
+#include <linux/sahara.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/wait.h>
@@ -32,7 +33,6 @@
#include "qaic_ras.h"
#include "qaic_ssr.h"
#include "qaic_timesync.h"
-#include "sahara.h"
MODULE_IMPORT_NS("DMA_BUF");
@@ -782,18 +782,12 @@ static int __init qaic_init(void)
ret = pci_register_driver(&qaic_pci_driver);
if (ret) {
pr_debug("qaic: pci_register_driver failed %d\n", ret);
- return ret;
+ goto free_pci;
}
ret = mhi_driver_register(&qaic_mhi_driver);
if (ret) {
pr_debug("qaic: mhi_driver_register failed %d\n", ret);
- goto free_pci;
- }
-
- ret = sahara_register();
- if (ret) {
- pr_debug("qaic: sahara_register failed %d\n", ret);
goto free_mhi;
}
@@ -847,7 +841,6 @@ static void __exit qaic_exit(void)
qaic_ras_unregister();
qaic_bootlog_unregister();
qaic_timesync_deinit();
- sahara_unregister();
mhi_driver_unregister(&qaic_mhi_driver);
pci_unregister_driver(&qaic_pci_driver);
}
diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
index b39a11e6c624ba00349cca22d74bd876020590ab..4acedb886adccc6f76f69c241d53106da59b491f 100644
--- a/drivers/bus/mhi/Kconfig
+++ b/drivers/bus/mhi/Kconfig
@@ -7,3 +7,4 @@
source "drivers/bus/mhi/host/Kconfig"
source "drivers/bus/mhi/ep/Kconfig"
+source "drivers/bus/mhi/sahara/Kconfig"
diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
index 354204b0ef3ae4030469a24a659f32429d592aef..e4af535e1bb1bc9481fae60d7eb347700d2e874c 100644
--- a/drivers/bus/mhi/Makefile
+++ b/drivers/bus/mhi/Makefile
@@ -3,3 +3,6 @@ obj-$(CONFIG_MHI_BUS) += host/
# Endpoint MHI stack
obj-$(CONFIG_MHI_BUS_EP) += ep/
+
+# Sahara MHI protocol
+obj-$(CONFIG_MHI_SAHARA) += sahara/
diff --git a/drivers/bus/mhi/sahara/Kconfig b/drivers/bus/mhi/sahara/Kconfig
new file mode 100644
index 0000000000000000000000000000000000000000..3f1caf6acd979a4af68aaf0e250aa54762e8cda5
--- /dev/null
+++ b/drivers/bus/mhi/sahara/Kconfig
@@ -0,0 +1,18 @@
+config MHI_SAHARA
+ tristate
+ depends on MHI_BUS
+ select FW_LOADER_COMPRESS
+ select FW_LOADER_COMPRESS_XZ
+ select FW_LOADER_COMPRESS_ZSTD
+ help
+ Enable support for the Sahara protocol transported over the MHI bus.
+
+ The Sahara protocol is used to transfer firmware images, retrieve
+ memory dumps and exchange command mode DDR calibration data between
+ host and device. This driver is not tied to a specific SoC and may be
+ used by multiple MHI based devices.
+
+ If unsure, say N.
+
+ To compile this driver as a module, choose M here: the module will be
+ called mhi_sahara.
diff --git a/drivers/bus/mhi/sahara/Makefile b/drivers/bus/mhi/sahara/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..fc02a25935011cbd7138ea8f24b88cf5b032a4ce
--- /dev/null
+++ b/drivers/bus/mhi/sahara/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_MHI_SAHARA) += mhi_sahara.o
+mhi_sahara-y := sahara.o
diff --git a/drivers/accel/qaic/sahara.c b/drivers/bus/mhi/sahara/sahara.c
similarity index 99%
rename from drivers/accel/qaic/sahara.c
rename to drivers/bus/mhi/sahara/sahara.c
index fd3c3b2d1fd3bb698809e6ca669128e2dce06613..8ff7b6425ac5423ef8f32117151dca10397686a8 100644
--- a/drivers/accel/qaic/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -1,6 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0-only
-
-/* Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. */
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
+ *
+ */
#include <linux/devcoredump.h>
#include <linux/firmware.h>
@@ -9,12 +11,11 @@
#include <linux/minmax.h>
#include <linux/mod_devicetable.h>
#include <linux/overflow.h>
+#include <linux/sahara.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
-#include "sahara.h"
-
#define SAHARA_HELLO_CMD 0x1 /* Min protocol version 1.0 */
#define SAHARA_HELLO_RESP_CMD 0x2 /* Min protocol version 1.0 */
#define SAHARA_READ_DATA_CMD 0x3 /* Min protocol version 1.0 */
@@ -928,8 +929,13 @@ int sahara_register(void)
{
return mhi_driver_register(&sahara_mhi_driver);
}
+module_init(sahara_register);
void sahara_unregister(void)
{
mhi_driver_unregister(&sahara_mhi_driver);
}
+module_exit(sahara_unregister);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Qualcomm Sahara MHI protocol driver");
diff --git a/drivers/accel/qaic/sahara.h b/include/linux/sahara.h
similarity index 100%
rename from drivers/accel/qaic/sahara.h
rename to include/linux/sahara.h
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 3/9] bus: mhi: Match devices exposing the protocol on the SAHARA channel
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
2026-03-19 6:31 ` [PATCH v4 1/9] Add documentation for Sahara protocol Kishore Batta
2026-03-19 6:31 ` [PATCH v4 2/9] bus: mhi: Move sahara protocol driver under drivers/bus/mhi Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 4/9] bus: mhi: Centralize firmware image table selection at probe time Kishore Batta
` (5 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
Some Qualcomm devices expose the Sahara protocol on a generic SAHARA MHI
channel rather than a QAIC specific channel name. As a result, the sahara
driver does not currently bind to such devices and never probes.
Extend the MHI device ID match table to also match the SAHARA channel
name. This allows the Sahara protocol driver to bind to devices that
expose the protocol directly on a standard sahara MHI channel.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index 8ff7b6425ac5423ef8f32117151dca10397686a8..e3499977e7c6b53bc624a8eb00d0636f2ea63307 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -911,8 +911,10 @@ static void sahara_mhi_dl_xfer_cb(struct mhi_device *mhi_dev, struct mhi_result
static const struct mhi_device_id sahara_mhi_match_table[] = {
{ .chan = "QAIC_SAHARA", },
+ { .chan = "SAHARA"},
{},
};
+MODULE_DEVICE_TABLE(mhi, sahara_mhi_match_table);
static struct mhi_driver sahara_mhi_driver = {
.id_table = sahara_mhi_match_table,
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 4/9] bus: mhi: Centralize firmware image table selection at probe time
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (2 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 3/9] bus: mhi: Match devices exposing the protocol on the SAHARA channel Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 5/9] bus: mhi: Add QDU100 variant and image_id firmware fallback Kishore Batta
` (4 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
The Sahara driver currently selects firmware image tables using
scattered, device specific conditionals in the probe path, making the
logic harder to follow and extend.
Refactor firmware image table selection into a single, explicit probe-time
mechanism by introducing a variant table that captures device matching,
firmware image tables, firmware folder names, and streaming behavior in
one place.
This centralizes device specific decisions, simplifies the probe logic,
and avoids ad-hoc conditionals while preserving the existing behavior for
all supported AIC devices.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 66 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 58 insertions(+), 8 deletions(-)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index e3499977e7c6b53bc624a8eb00d0636f2ea63307..8f1c0d72066c0cf80c09d78bfc51df2e482133b9 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -180,6 +180,16 @@ struct sahara_context {
u32 read_data_length;
bool is_mem_dump_mode;
bool non_streaming;
+ const char *fw_folder;
+};
+
+struct sahara_variant {
+ const char *match;
+ bool match_is_chan;
+ const char * const *image_table;
+ size_t table_size;
+ const char *fw_folder;
+ bool non_streaming;
};
static const char * const aic100_image_table[] = {
@@ -224,11 +234,50 @@ static const char * const aic200_image_table[] = {
[78] = "qcom/aic200/pvs.bin",
};
+static const struct sahara_variant sahara_variants[] = {
+ {
+ .match = "AIC100",
+ .match_is_chan = false,
+ .image_table = aic100_image_table,
+ .table_size = ARRAY_SIZE(aic100_image_table),
+ .fw_folder = "aic100",
+ .non_streaming = true,
+ },
+ {
+ .match = "AIC200",
+ .match_is_chan = false,
+ .image_table = aic200_image_table,
+ .table_size = ARRAY_SIZE(aic200_image_table),
+ .fw_folder = "aic200",
+ .non_streaming = false,
+ }
+};
+
static bool is_streaming(struct sahara_context *context)
{
return !context->non_streaming;
}
+static const struct sahara_variant *sahara_select_variant(struct mhi_device *mhi_dev,
+ const struct mhi_device_id *id)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(sahara_variants); i++) {
+ const struct sahara_variant *v = &sahara_variants[i];
+
+ if (v->match_is_chan) {
+ if (id && id->chan && !strcmp(id->chan, v->match))
+ return v;
+ } else {
+ if (mhi_dev->mhi_cntrl && mhi_dev->mhi_cntrl->name &&
+ !strcmp(mhi_dev->mhi_cntrl->name, v->match))
+ return v;
+ }
+ }
+ return NULL;
+}
+
static int sahara_find_image(struct sahara_context *context, u32 image_id)
{
int ret;
@@ -797,6 +846,7 @@ static void sahara_read_data_processing(struct work_struct *work)
static int sahara_mhi_probe(struct mhi_device *mhi_dev, const struct mhi_device_id *id)
{
+ const struct sahara_variant *variant;
struct sahara_context *context;
int ret;
int i;
@@ -809,14 +859,14 @@ static int sahara_mhi_probe(struct mhi_device *mhi_dev, const struct mhi_device_
if (!context->rx)
return -ENOMEM;
- if (!strcmp(mhi_dev->mhi_cntrl->name, "AIC200")) {
- context->image_table = aic200_image_table;
- context->table_size = ARRAY_SIZE(aic200_image_table);
- } else {
- context->image_table = aic100_image_table;
- context->table_size = ARRAY_SIZE(aic100_image_table);
- context->non_streaming = true;
- }
+ variant = sahara_select_variant(mhi_dev, id);
+ if (!variant)
+ return -ENODEV;
+
+ context->image_table = variant->image_table;
+ context->table_size = variant->table_size;
+ context->non_streaming = variant->non_streaming;
+ context->fw_folder = variant->fw_folder;
/*
* There are two firmware implementations for READ_DATA handling.
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 5/9] bus: mhi: Add QDU100 variant and image_id firmware fallback
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (3 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 4/9] bus: mhi: Centralize firmware image table selection at probe time Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 6/9] bus: mhi: Load DDR training data using per-device serial number Kishore Batta
` (3 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
The Sahara driver currently selects a firmware image table based on the
attached device, but it does not recognize QDU100 devices that expose the
protocol on the SAHARA MHI channel. As a result, the host cannot associate
QDU100 devices with the correct firmware namespace during image transfer.
Extend the probe-time variant selection to match the SAHARA MHI channel
and associate it with the QDU100 firmware folder. Add an image_id based
firmware lookup fallback for cases where an image does not have an explicit
table entry. This allows required images to be provisioned by the platform
without requiring device specific client drivers or additional registration
mechanisms.
This change only affects devices matched on the SAHARA channel and does not
change behavior for existing AIC100 and AIC200 devices.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 77 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 72 insertions(+), 5 deletions(-)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index 8f1c0d72066c0cf80c09d78bfc51df2e482133b9..4ea14c57774f51a778289d7409372a6ab21fea60 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -234,6 +234,36 @@ static const char * const aic200_image_table[] = {
[78] = "qcom/aic200/pvs.bin",
};
+static const char * const qdu100_image_table[] = {
+ [5] = "qcom/qdu100/uefi.elf",
+ [8] = "qcom/qdu100/qdsp6sw.mbn",
+ [16] = "qcom/qdu100/efs1.bin",
+ [17] = "qcom/qdu100/efs2.bin",
+ [20] = "qcom/qdu100/efs3.bin",
+ [23] = "qcom/qdu100/aop.mbn",
+ [25] = "qcom/qdu100/tz.mbn",
+ [29] = "qcom/qdu100/zeros_1sector.bin",
+ [33] = "qcom/qdu100/hypvm.mbn",
+ [34] = "qcom/qdu100/mdmddr.mbn",
+ [36] = "qcom/qdu100/multi_image_qti.mbn",
+ [37] = "qcom/qdu100/multi_image.mbn",
+ [38] = "qcom/qdu100/xbl_config.elf",
+ [39] = "qcom/qdu100/abl_userdebug.elf",
+ [40] = "qcom/qdu100/zeros_1sector.bin",
+ [41] = "qcom/qdu100/devcfg.mbn",
+ [42] = "qcom/qdu100/zeros_1sector.bin",
+ [45] = "qcom/qdu100/tools_l.elf",
+ [46] = "qcom/qdu100/Quantum.elf",
+ [47] = "qcom/qdu100/quest.elf",
+ [48] = "qcom/qdu100/xbl_ramdump.elf",
+ [49] = "qcom/qdu100/shrm.elf",
+ [50] = "qcom/qdu100/cpucp.elf",
+ [51] = "qcom/qdu100/aop_devcfg.mbn",
+ [52] = "qcom/qdu100/fw_csm_gsi_3.0.elf",
+ [53] = "qcom/qdu100/qdsp6sw_dtbs.elf",
+ [54] = "qcom/qdu100/qupv3fw.elf",
+};
+
static const struct sahara_variant sahara_variants[] = {
{
.match = "AIC100",
@@ -250,6 +280,14 @@ static const struct sahara_variant sahara_variants[] = {
.table_size = ARRAY_SIZE(aic200_image_table),
.fw_folder = "aic200",
.non_streaming = false,
+ },
+ {
+ .match = "SAHARA",
+ .match_is_chan = true,
+ .image_table = qdu100_image_table,
+ .table_size = ARRAY_SIZE(qdu100_image_table),
+ .fw_folder = "qdu100",
+ .non_streaming = false,
}
};
@@ -278,8 +316,21 @@ static const struct sahara_variant *sahara_select_variant(struct mhi_device *mhi
return NULL;
}
+static int sahara_request_fw(struct sahara_context *context, const char *path)
+{
+ int ret;
+
+ ret = firmware_request_nowarn(&context->firmware, path,
+ &context->mhi_dev->dev);
+ if (ret)
+ dev_dbg(&context->mhi_dev->dev,
+ "Request for file %s failed %d\n", path, ret);
+ return ret;
+}
+
static int sahara_find_image(struct sahara_context *context, u32 image_id)
{
+ char *fw_path;
int ret;
if (image_id == context->active_image_id)
@@ -292,8 +343,26 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
}
if (image_id >= context->table_size || !context->image_table[image_id]) {
- dev_err(&context->mhi_dev->dev, "request for unknown image: %d\n", image_id);
- return -EINVAL;
+ if (!context->fw_folder) {
+ dev_err(&context->mhi_dev->dev,
+ "Request for unknown image: %u (no fw folder)\n", image_id);
+ return -EINVAL;
+ }
+
+ fw_path = kasprintf(GFP_KERNEL, "qcom/%s/image_%u.elf",
+ context->fw_folder, image_id);
+ if (!fw_path)
+ return -ENOMEM;
+
+ ret = sahara_request_fw(context, fw_path);
+ kfree(fw_path);
+ if (ret) {
+ dev_err(&context->mhi_dev->dev,
+ "request for unknown image: %d\n", image_id);
+ return -EINVAL;
+ }
+ context->active_image_id = image_id;
+ return 0;
}
/*
@@ -301,9 +370,7 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
* Only the device knows. Suppress error messages that could suggest an
* a problem when we were actually able to continue.
*/
- ret = firmware_request_nowarn(&context->firmware,
- context->image_table[image_id],
- &context->mhi_dev->dev);
+ ret = sahara_request_fw(context, context->image_table[image_id]);
if (ret) {
dev_dbg(&context->mhi_dev->dev, "request for image id %d / file %s failed %d\n",
image_id, context->image_table[image_id], ret);
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 6/9] bus: mhi: Load DDR training data using per-device serial number
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (4 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 5/9] bus: mhi: Add QDU100 variant and image_id firmware fallback Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode Kishore Batta
` (2 subsequent siblings)
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
Devices may provide device-specific DDR training data that can be reused
across boot to avoid retraining and reduce boot time. The Sahara driver
currently always falls back to the default DDR training image, even when
per-device training data is available.
Extend the firmware loading logic to first attempt loading a per-device
DDR training image using the device serial number. If the serial-specific
image is not present, fallback to the existing default image, preserving
current behavior.
This change enables DDR training data reuse when available while keeping
the existing training flow unchanged for devices without saved data.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 47 ++++++++++++++++++++++++++++++++---------
1 file changed, 37 insertions(+), 10 deletions(-)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index 4ea14c57774f51a778289d7409372a6ab21fea60..0a0f578aaa47ab2c4ca0765666b392fb9936ddd5 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -61,6 +61,8 @@
#define SAHARA_MEM_DEBUG64_LENGTH 0x18
#define SAHARA_MEM_READ64_LENGTH 0x18
+#define SAHARA_DDR_TRAINING_IMG_ID 34
+
struct sahara_packet {
__le32 cmd;
__le32 length;
@@ -365,16 +367,41 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
return 0;
}
- /*
- * This image might be optional. The device may continue without it.
- * Only the device knows. Suppress error messages that could suggest an
- * a problem when we were actually able to continue.
- */
- ret = sahara_request_fw(context, context->image_table[image_id]);
- if (ret) {
- dev_dbg(&context->mhi_dev->dev, "request for image id %d / file %s failed %d\n",
- image_id, context->image_table[image_id], ret);
- return ret;
+ /* DDR training special case: Try per-serial number file first */
+ if (image_id == SAHARA_DDR_TRAINING_IMG_ID && context->fw_folder) {
+ u32 serial_num = context->mhi_dev->mhi_cntrl->serial_number;
+
+ fw_path = kasprintf(GFP_KERNEL,
+ "qcom/%s/mdmddr_0x%x.mbn",
+ context->fw_folder, serial_num);
+ if (!fw_path)
+ return -ENOMEM;
+
+ ret = sahara_request_fw(context, fw_path);
+ kfree(fw_path);
+
+ if (ret) {
+ ret = sahara_request_fw(context, context->image_table[image_id]);
+ if (ret) {
+ dev_dbg(&context->mhi_dev->dev,
+ "request for image id %d / file %s failed %d\n",
+ image_id, context->image_table[image_id], ret);
+ }
+ return ret;
+ }
+ } else {
+ /*
+ * This image might be optional. The device may continue without it.
+ * Only the device knows. Suppress error messages that could suggest an
+ * a problem when we were actually able to continue.
+ */
+ ret = sahara_request_fw(context, context->image_table[image_id]);
+ if (ret) {
+ dev_dbg(&context->mhi_dev->dev,
+ "request for image id %d / file %s failed %d\n",
+ image_id, context->image_table[image_id], ret);
+ return ret;
+ }
}
context->active_image_id = image_id;
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (5 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 6/9] bus: mhi: Load DDR training data using per-device serial number Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-22 17:39 ` kernel test robot
2026-03-19 6:31 ` [PATCH v4 8/9] bus: mhi: Expose DDR training data via controller sysfs Kishore Batta
2026-03-19 6:31 ` [PATCH v4 9/9] Documentation: ABI: Add sysfs ABI documentation for DDR training data Kishore Batta
8 siblings, 1 reply; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
During early boot, devices may perform DDR training and produce training
data that can be reused on subsequent boots to reduce initialization
time. The sahara protocol provides a command mode flow to transfer this
training data to the host, but the driver currently does not handle
command mode and drops the training payload.
Add Sahara command mode support to retrieve DDR training data from the
device. When the device enters command mode and sends CMD_READY, query
the support command list and request DDR training data using EXECUTE and
EXECUTE_DATA. Allocate receive buffers based on the reported response
size and copy the raw payload directly from the MHI DL completion
callback.
Store the captured training data in controller-scoped memory using devres,
so it remains available after sahara channel teardown. Also distinguish
raw payload completion from control packets in the DL callback, avoiding
misinterpretation of training data as protocol messages, and requeue
the RX buffer after switching back to IMAGE_TX_PENDING to allow the
boot flow to continue.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 328 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 320 insertions(+), 8 deletions(-)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index 0a0f578aaa47ab2c4ca0765666b392fb9936ddd5..c88f1220199ac4373d3552167870c19a0d5f23b9 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -5,11 +5,14 @@
*/
#include <linux/devcoredump.h>
+#include <linux/device.h>
+#include <linux/device/devres.h>
#include <linux/firmware.h>
#include <linux/limits.h>
#include <linux/mhi.h>
#include <linux/minmax.h>
#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
#include <linux/overflow.h>
#include <linux/sahara.h>
#include <linux/types.h>
@@ -60,8 +63,16 @@
#define SAHARA_RESET_LENGTH 0x8
#define SAHARA_MEM_DEBUG64_LENGTH 0x18
#define SAHARA_MEM_READ64_LENGTH 0x18
-
+#define SAHARA_COMMAND_READY_LENGTH 0x8
+#define SAHARA_COMMAND_EXEC_RESP_LENGTH 0x10
+#define SAHARA_COMMAND_EXECUTE_LENGTH 0xc
+#define SAHARA_COMMAND_EXEC_DATA_LENGTH 0xc
+#define SAHARA_SWITCH_MODE_LENGTH 0xc
+
+#define SAHARA_EXEC_CMD_GET_COMMAND_ID_LIST 0x8
+#define SAHARA_EXEC_CMD_GET_TRAINING_DATA 0x9
#define SAHARA_DDR_TRAINING_IMG_ID 34
+#define SAHARA_NUM_CMD_BUF SAHARA_NUM_TX_BUF
struct sahara_packet {
__le32 cmd;
@@ -97,6 +108,19 @@ struct sahara_packet {
__le64 memory_address;
__le64 memory_length;
} memory_read64;
+ struct {
+ __le32 client_command;
+ } command_execute;
+ struct {
+ __le32 client_command;
+ __le32 response_length;
+ } command_execute_resp;
+ struct {
+ __le32 client_command;
+ } command_exec_data;
+ struct {
+ __le32 mode;
+ } mode_switch;
};
};
@@ -163,6 +187,7 @@ struct sahara_context {
struct work_struct fw_work;
struct work_struct dump_work;
struct work_struct read_data_work;
+ struct work_struct cmd_work;
struct mhi_device *mhi_dev;
const char * const *image_table;
u32 table_size;
@@ -183,6 +208,24 @@ struct sahara_context {
bool is_mem_dump_mode;
bool non_streaming;
const char *fw_folder;
+ bool is_cmd_mode;
+ bool receiving_trng_data;
+ size_t trng_size;
+ size_t trng_rcvd;
+ u32 trng_nbuf;
+ char *cmd_buff[SAHARA_NUM_CMD_BUF];
+};
+
+/*
+ * Controller-scoped training data store (per MHI controller device).
+ * Stored as devres resource on mhi_dev->mhi_cntrl->mhi_dev->dev.
+ */
+struct sahara_ctrl_trng_data {
+ struct mutex lock; /* Protects data, size, copied and receiving */
+ void *data;
+ size_t size;
+ size_t copied;
+ bool receiving;
};
struct sahara_variant {
@@ -330,6 +373,48 @@ static int sahara_request_fw(struct sahara_context *context, const char *path)
return ret;
}
+static void sahara_ctrl_trng_release(struct device *dev, void *res)
+{
+ struct sahara_ctrl_trng_data *ct = res;
+
+ mutex_lock(&ct->lock);
+ kfree(ct->data);
+ ct->data = NULL;
+ ct->size = 0;
+ ct->copied = 0;
+ ct->receiving = false;
+ mutex_unlock(&ct->lock);
+}
+
+static int sahara_ctrl_trng_match(struct device *dev, void *res, void *match_data)
+{
+ /* Exactly one instance per controller */
+ return 1;
+}
+
+static struct sahara_ctrl_trng_data *sahara_ctrl_trng_get(struct device *dev)
+{
+ struct sahara_ctrl_trng_data *ct;
+
+ ct = devres_find(dev, sahara_ctrl_trng_release,
+ sahara_ctrl_trng_match, NULL);
+ if (ct)
+ return ct;
+
+ ct = devres_alloc(sahara_ctrl_trng_release, sizeof(*ct), GFP_KERNEL);
+ if (!ct)
+ return NULL;
+
+ mutex_init(&ct->lock);
+ ct->data = NULL;
+ ct->size = 0;
+ ct->copied = 0;
+ ct->receiving = false;
+
+ devres_add(dev, ct);
+ return ct;
+}
+
static int sahara_find_image(struct sahara_context *context, u32 image_id)
{
char *fw_path;
@@ -423,6 +508,11 @@ static void sahara_send_reset(struct sahara_context *context)
context->is_mem_dump_mode = false;
context->read_data_offset = 0;
context->read_data_length = 0;
+ context->is_cmd_mode = false;
+ context->receiving_trng_data = false;
+ context->trng_size = 0;
+ context->trng_rcvd = 0;
+ context->trng_nbuf = 0;
context->tx[0]->cmd = cpu_to_le32(SAHARA_RESET_CMD);
context->tx[0]->length = cpu_to_le32(SAHARA_RESET_LENGTH);
@@ -458,7 +548,8 @@ static void sahara_hello(struct sahara_context *context)
if (le32_to_cpu(context->rx->hello.mode) != SAHARA_MODE_IMAGE_TX_PENDING &&
le32_to_cpu(context->rx->hello.mode) != SAHARA_MODE_IMAGE_TX_COMPLETE &&
- le32_to_cpu(context->rx->hello.mode) != SAHARA_MODE_MEMORY_DEBUG) {
+ le32_to_cpu(context->rx->hello.mode) != SAHARA_MODE_MEMORY_DEBUG &&
+ le32_to_cpu(context->rx->hello.mode) != SAHARA_MODE_COMMAND) {
dev_err(&context->mhi_dev->dev, "Unsupported hello packet - mode %d\n",
le32_to_cpu(context->rx->hello.mode));
return;
@@ -477,6 +568,153 @@ static void sahara_hello(struct sahara_context *context)
dev_err(&context->mhi_dev->dev, "Unable to send hello response %d\n", ret);
}
+static void sahara_switch_mode_to_img_tx(struct sahara_context *context)
+{
+ int ret;
+
+ context->tx[0]->cmd = cpu_to_le32(SAHARA_SWITCH_MODE_CMD);
+ context->tx[0]->length = cpu_to_le32(SAHARA_SWITCH_MODE_LENGTH);
+ context->tx[0]->mode_switch.mode = cpu_to_le32(SAHARA_MODE_IMAGE_TX_PENDING);
+
+ ret = mhi_queue_buf(context->mhi_dev, DMA_TO_DEVICE, context->tx[0],
+ SAHARA_SWITCH_MODE_LENGTH, MHI_EOT);
+
+ if (ret)
+ dev_err(&context->mhi_dev->dev, "Unable to send mode switch %d\n", ret);
+}
+
+static void sahara_command_execute(struct sahara_context *context, u32 client_command)
+{
+ int ret;
+
+ context->tx[0]->cmd = cpu_to_le32(SAHARA_EXECUTE_CMD);
+ context->tx[0]->length = cpu_to_le32(SAHARA_COMMAND_EXECUTE_LENGTH);
+ context->tx[0]->command_execute.client_command = cpu_to_le32(client_command);
+
+ ret = mhi_queue_buf(context->mhi_dev, DMA_TO_DEVICE, context->tx[0],
+ SAHARA_COMMAND_EXECUTE_LENGTH, MHI_EOT);
+ if (ret)
+ dev_err(&context->mhi_dev->dev, "Unable to send command execute %d\n", ret);
+}
+
+static void sahara_command_execute_data(struct sahara_context *context, u32 client_command)
+{
+ int ret;
+
+ context->tx[0]->cmd = cpu_to_le32(SAHARA_EXECUTE_DATA_CMD);
+ context->tx[0]->length = cpu_to_le32(SAHARA_COMMAND_EXEC_DATA_LENGTH);
+ context->tx[0]->command_exec_data.client_command = cpu_to_le32(client_command);
+
+ ret = mhi_queue_buf(context->mhi_dev, DMA_TO_DEVICE, context->tx[0],
+ SAHARA_COMMAND_EXEC_DATA_LENGTH, MHI_EOT);
+ if (ret)
+ dev_err(&context->mhi_dev->dev, "Unable to send execute data %d\n", ret);
+}
+
+static void sahara_command_ready(struct sahara_context *context)
+{
+ if (le32_to_cpu(context->rx->length) != SAHARA_COMMAND_READY_LENGTH) {
+ dev_err(&context->mhi_dev->dev,
+ "Malformed command ready packet - length %u\n",
+ le32_to_cpu(context->rx->length));
+ return;
+ }
+
+ context->is_cmd_mode = true;
+ context->receiving_trng_data = false;
+
+ sahara_command_execute(context, SAHARA_EXEC_CMD_GET_COMMAND_ID_LIST);
+}
+
+static void sahara_command_execute_resp(struct sahara_context *context)
+{
+ struct device *dev = &context->mhi_dev->mhi_cntrl->mhi_dev->dev;
+ struct sahara_ctrl_trng_data *ct;
+ u32 client_cmd, resp_len;
+ int ret;
+ u64 remaining;
+ u32 i;
+
+ if (le32_to_cpu(context->rx->length) != SAHARA_COMMAND_EXEC_RESP_LENGTH ||
+ le32_to_cpu(context->rx->command_execute_resp.response_length) < 0) {
+ dev_err(&context->mhi_dev->dev,
+ "Malformed command execute resp packet - length %d\n",
+ le32_to_cpu(context->rx->length));
+ return;
+ }
+
+ client_cmd = le32_to_cpu(context->rx->command_execute_resp.client_command);
+ resp_len = le32_to_cpu(context->rx->command_execute_resp.response_length);
+
+ sahara_command_execute_data(context, client_cmd);
+
+ if (client_cmd == SAHARA_EXEC_CMD_GET_COMMAND_ID_LIST) {
+ sahara_command_execute(context, SAHARA_EXEC_CMD_GET_TRAINING_DATA);
+ return;
+ }
+
+ if (client_cmd != SAHARA_EXEC_CMD_GET_TRAINING_DATA)
+ return;
+
+ ct = sahara_ctrl_trng_get(dev);
+ if (!ct) {
+ context->is_cmd_mode = false;
+ sahara_switch_mode_to_img_tx(context);
+ return;
+ }
+
+ mutex_lock(&ct->lock);
+ kfree(ct->data);
+ ct->data = kzalloc(resp_len, GFP_KERNEL);
+ ct->size = resp_len;
+ ct->copied = 0;
+ ct->receiving = true;
+ mutex_unlock(&ct->lock);
+
+ if (!ct->data) {
+ context->is_cmd_mode = false;
+ sahara_switch_mode_to_img_tx(context);
+ return;
+ }
+
+ context->trng_size = resp_len;
+ context->trng_rcvd = 0;
+ context->receiving_trng_data = true;
+
+ remaining = resp_len;
+ for (i = 0; i < SAHARA_NUM_CMD_BUF && remaining; i++) {
+ size_t pkt = min_t(size_t, remaining, SAHARA_PACKET_MAX_SIZE);
+
+ ret = mhi_queue_buf(context->mhi_dev, DMA_FROM_DEVICE,
+ context->cmd_buff[i], pkt,
+ (remaining <= pkt) ? MHI_EOT : MHI_CHAIN);
+ if (ret)
+ break;
+
+ remaining -= pkt;
+ }
+
+ context->trng_nbuf = i;
+}
+
+static void sahara_command_processing(struct work_struct *work)
+{
+ struct sahara_context *context = container_of(work, struct sahara_context, cmd_work);
+ int ret;
+
+ if (le32_to_cpu(context->rx->cmd) == SAHARA_EXECUTE_RESP_CMD)
+ sahara_command_execute_resp(context);
+
+ if (!context->receiving_trng_data) {
+ ret = mhi_queue_buf(context->mhi_dev, DMA_FROM_DEVICE,
+ context->rx, SAHARA_PACKET_MAX_SIZE, MHI_EOT);
+
+ if (ret)
+ dev_err(&context->mhi_dev->dev,
+ "Unable to requeue rx buf %d\n", ret);
+ }
+}
+
static int read_data_helper(struct sahara_context *context, int buf_index)
{
enum mhi_flags mhi_flag;
@@ -703,6 +941,9 @@ static void sahara_processing(struct work_struct *work)
case SAHARA_MEM_DEBUG64_CMD:
sahara_memory_debug64(context);
break;
+ case SAHARA_CMD_READY_CMD:
+ sahara_command_ready(context);
+ break;
default:
dev_err(&context->mhi_dev->dev, "Unknown command %d\n",
le32_to_cpu(context->rx->cmd));
@@ -1003,6 +1244,20 @@ static int sahara_mhi_probe(struct mhi_device *mhi_dev, const struct mhi_device_
INIT_WORK(&context->fw_work, sahara_processing);
INIT_WORK(&context->dump_work, sahara_dump_processing);
INIT_WORK(&context->read_data_work, sahara_read_data_processing);
+ INIT_WORK(&context->cmd_work, sahara_command_processing);
+
+ for (i = 0; i < SAHARA_NUM_CMD_BUF; i++) {
+ context->cmd_buff[i] = devm_kzalloc(&mhi_dev->dev,
+ SAHARA_PACKET_MAX_SIZE, GFP_KERNEL);
+ if (!context->cmd_buff[i])
+ return -ENOMEM;
+ }
+
+ context->is_cmd_mode = false;
+ context->receiving_trng_data = false;
+ context->trng_size = 0;
+ context->trng_rcvd = 0;
+ context->trng_nbuf = 0;
context->active_image_id = SAHARA_IMAGE_ID_NONE;
dev_set_drvdata(&mhi_dev->dev, context);
@@ -1026,6 +1281,7 @@ static void sahara_mhi_remove(struct mhi_device *mhi_dev)
cancel_work_sync(&context->fw_work);
cancel_work_sync(&context->dump_work);
+ cancel_work_sync(&context->cmd_work);
vfree(context->mem_dump);
sahara_release_image(context);
mhi_unprepare_from_transfer(mhi_dev);
@@ -1042,15 +1298,71 @@ static void sahara_mhi_ul_xfer_cb(struct mhi_device *mhi_dev, struct mhi_result
static void sahara_mhi_dl_xfer_cb(struct mhi_device *mhi_dev, struct mhi_result *mhi_result)
{
struct sahara_context *context = dev_get_drvdata(&mhi_dev->dev);
+ struct sahara_ctrl_trng_data *ct;
+ struct device *dev;
+ size_t copy;
+ int ret;
+ u32 i;
+
+ if (mhi_result->transaction_status)
+ return;
+
+ /*
+ * Raw training payload completions arrive for cmd_buff[] buffers.
+ * Do not schedule cmd_work for those.
+ */
+ if (context->is_cmd_mode && context->receiving_trng_data &&
+ mhi_result->buf_addr != context->rx) {
+ dev = &context->mhi_dev->mhi_cntrl->mhi_dev->dev;
+ ct = sahara_ctrl_trng_get(dev);
+ if (!ct)
+ return;
- if (!mhi_result->transaction_status) {
- context->rx_size = mhi_result->bytes_xferd;
- if (context->is_mem_dump_mode)
- schedule_work(&context->dump_work);
- else
- schedule_work(&context->fw_work);
+ for (i = 0; i < context->trng_nbuf; i++) {
+ if (mhi_result->buf_addr == context->cmd_buff[i]) {
+ mutex_lock(&ct->lock);
+ copy = min_t(size_t, mhi_result->bytes_xferd,
+ ct->size - ct->copied);
+ memcpy((u8 *)ct->data + ct->copied,
+ mhi_result->buf_addr, copy);
+ ct->copied += copy;
+ mutex_unlock(&ct->lock);
+
+ context->trng_rcvd += copy;
+
+ if (context->trng_rcvd >= context->trng_size) {
+ mutex_lock(&ct->lock);
+ ct->receiving = false;
+ mutex_unlock(&ct->lock);
+
+ context->receiving_trng_data = false;
+ context->is_cmd_mode = false;
+
+ sahara_switch_mode_to_img_tx(context);
+ ret = mhi_queue_buf(context->mhi_dev,
+ DMA_FROM_DEVICE,
+ context->rx,
+ SAHARA_PACKET_MAX_SIZE,
+ MHI_EOT);
+ if (ret)
+ dev_err(&context->mhi_dev->dev,
+ "Unable to requeue rx buf %d\n", ret);
+ }
+ return;
+ }
+ }
+ return;
}
+ /* Normal Rx completion */
+ context->rx_size = mhi_result->bytes_xferd;
+ if (context->is_mem_dump_mode)
+ schedule_work(&context->dump_work);
+ else if (context->is_cmd_mode)
+ schedule_work(&context->cmd_work);
+ else
+ schedule_work(&context->fw_work);
+
}
static const struct mhi_device_id sahara_mhi_match_table[] = {
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode
2026-03-19 6:31 ` [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode Kishore Batta
@ 2026-03-22 17:39 ` kernel test robot
0 siblings, 0 replies; 11+ messages in thread
From: kernel test robot @ 2026-03-22 17:39 UTC (permalink / raw)
To: Kishore Batta, Jonathan Corbet, Shuah Khan, Jeff Hugo,
Carl Vanderlip, Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: oe-kbuild-all, linux-doc, linux-kernel, linux-arm-msm, dri-devel,
mhi, Kishore Batta
Hi Kishore,
kernel test robot noticed the following build warnings:
[auto build test WARNING on a0ae2a256046c0c5d3778d1a194ff2e171f16e5f]
url: https://github.com/intel-lab-lkp/linux/commits/Kishore-Batta/Add-documentation-for-Sahara-protocol/20260320-144614
base: a0ae2a256046c0c5d3778d1a194ff2e171f16e5f
patch link: https://lore.kernel.org/r/20260319-sahara_protocol_new_v2-v4-7-47ad79308762%40oss.qualcomm.com
patch subject: [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode
config: i386-randconfig-141-20260322 (https://download.01.org/0day-ci/archive/20260323/202603230107.6EzMoVPn-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
smatch: v0.5.0-9004-gb810ac53
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603230107.6EzMoVPn-lkp@intel.com/
New smatch warnings:
drivers/bus/mhi/sahara/sahara.c:639 sahara_command_execute_resp() warn: unsigned '(context->rx->command_execute_resp.response_length)' is never less than zero.
Old smatch warnings:
drivers/bus/mhi/sahara/sahara.c:353 sahara_select_variant() warn: this array is probably non-NULL. 'id->chan'
vim +639 drivers/bus/mhi/sahara/sahara.c
628
629 static void sahara_command_execute_resp(struct sahara_context *context)
630 {
631 struct device *dev = &context->mhi_dev->mhi_cntrl->mhi_dev->dev;
632 struct sahara_ctrl_trng_data *ct;
633 u32 client_cmd, resp_len;
634 int ret;
635 u64 remaining;
636 u32 i;
637
638 if (le32_to_cpu(context->rx->length) != SAHARA_COMMAND_EXEC_RESP_LENGTH ||
> 639 le32_to_cpu(context->rx->command_execute_resp.response_length) < 0) {
640 dev_err(&context->mhi_dev->dev,
641 "Malformed command execute resp packet - length %d\n",
642 le32_to_cpu(context->rx->length));
643 return;
644 }
645
646 client_cmd = le32_to_cpu(context->rx->command_execute_resp.client_command);
647 resp_len = le32_to_cpu(context->rx->command_execute_resp.response_length);
648
649 sahara_command_execute_data(context, client_cmd);
650
651 if (client_cmd == SAHARA_EXEC_CMD_GET_COMMAND_ID_LIST) {
652 sahara_command_execute(context, SAHARA_EXEC_CMD_GET_TRAINING_DATA);
653 return;
654 }
655
656 if (client_cmd != SAHARA_EXEC_CMD_GET_TRAINING_DATA)
657 return;
658
659 ct = sahara_ctrl_trng_get(dev);
660 if (!ct) {
661 context->is_cmd_mode = false;
662 sahara_switch_mode_to_img_tx(context);
663 return;
664 }
665
666 mutex_lock(&ct->lock);
667 kfree(ct->data);
668 ct->data = kzalloc(resp_len, GFP_KERNEL);
669 ct->size = resp_len;
670 ct->copied = 0;
671 ct->receiving = true;
672 mutex_unlock(&ct->lock);
673
674 if (!ct->data) {
675 context->is_cmd_mode = false;
676 sahara_switch_mode_to_img_tx(context);
677 return;
678 }
679
680 context->trng_size = resp_len;
681 context->trng_rcvd = 0;
682 context->receiving_trng_data = true;
683
684 remaining = resp_len;
685 for (i = 0; i < SAHARA_NUM_CMD_BUF && remaining; i++) {
686 size_t pkt = min_t(size_t, remaining, SAHARA_PACKET_MAX_SIZE);
687
688 ret = mhi_queue_buf(context->mhi_dev, DMA_FROM_DEVICE,
689 context->cmd_buff[i], pkt,
690 (remaining <= pkt) ? MHI_EOT : MHI_CHAIN);
691 if (ret)
692 break;
693
694 remaining -= pkt;
695 }
696
697 context->trng_nbuf = i;
698 }
699
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v4 8/9] bus: mhi: Expose DDR training data via controller sysfs
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (6 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
2026-03-19 6:31 ` [PATCH v4 9/9] Documentation: ABI: Add sysfs ABI documentation for DDR training data Kishore Batta
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
DDR training data captured during Sahara command mode needs to be
accessible to userspace so it can be persisted and reused on subsequent
boots. Currently, the training data is stored internally in the driver
but has no external visibility once the sahara channel is torn down.
Expose the captured DDR training data via a read-only binary sysfs
attribute on the MHI controller device. The sysfs file is created under
the controller node, allowing userspace to read the training data even
after the sahara channel device has been removed.
The sysfs attribute reads directly from controller-scoped storage and
relies on device managed resources for cleanup when the controller
device is destroyed. No explicit sysfs removal is required, avoiding
lifetime dependencies on the Sahara channel device.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
drivers/bus/mhi/sahara/sahara.c | 69 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 69 insertions(+)
diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index c88f1220199ac4373d3552167870c19a0d5f23b9..b7208738df10fc3c3895acd46873412818dc1730 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -415,6 +415,73 @@ static struct sahara_ctrl_trng_data *sahara_ctrl_trng_get(struct device *dev)
return ct;
}
+static ssize_t ddr_training_data_read(struct file *filp, struct kobject *kobj,
+ const struct bin_attribute *attr, char *buf,
+ loff_t offset, size_t count)
+{
+ struct device *dev = kobj_to_dev(kobj);
+ struct sahara_ctrl_trng_data *ct;
+ size_t available;
+
+ ct = sahara_ctrl_trng_get(dev);
+ if (!ct)
+ return -ENODEV;
+
+ mutex_lock(&ct->lock);
+
+ /* No data yet or offset past end */
+ if (!ct->data || offset >= ct->size) {
+ mutex_unlock(&ct->lock);
+ return 0;
+ }
+
+ available = ct->size - offset;
+ count = min(count, available);
+ memcpy(buf, (u8 *)ct->data + offset, count);
+
+ mutex_unlock(&ct->lock);
+
+ return count;
+}
+
+static const struct bin_attribute ddr_training_data_attr = {
+ .attr = {
+ .name = "ddr_training_data",
+ .mode = 0444,
+ },
+ .read = ddr_training_data_read,
+};
+
+static void sahara_sysfs_devres_release(struct device *dev, void *res)
+{
+ device_remove_bin_file(dev, &ddr_training_data_attr);
+}
+
+static void sahara_sysfs_create(struct mhi_device *mhi_dev)
+{
+ struct device *dev = &mhi_dev->mhi_cntrl->mhi_dev->dev;
+ void *cookie;
+ int ret;
+
+ if (devres_find(dev, sahara_sysfs_devres_release, NULL, NULL))
+ return;
+
+ ret = device_create_bin_file(dev, &ddr_training_data_attr);
+ if (ret) {
+ dev_warn(&mhi_dev->dev,
+ "Failed to create DDR training sysfs node (%d)\n", ret);
+ return;
+ }
+
+ cookie = devres_alloc(sahara_sysfs_devres_release, 1, GFP_KERNEL);
+ if (!cookie) {
+ device_remove_bin_file(dev, &ddr_training_data_attr);
+ return;
+ }
+
+ devres_add(dev, cookie);
+}
+
static int sahara_find_image(struct sahara_context *context, u32 image_id)
{
char *fw_path;
@@ -1272,6 +1339,8 @@ static int sahara_mhi_probe(struct mhi_device *mhi_dev, const struct mhi_device_
return ret;
}
+ sahara_sysfs_create(mhi_dev);
+
return 0;
}
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v4 9/9] Documentation: ABI: Add sysfs ABI documentation for DDR training data
2026-03-19 6:31 [PATCH v4 0/9] Qualcomm Sahara protocol enhancements Kishore Batta
` (7 preceding siblings ...)
2026-03-19 6:31 ` [PATCH v4 8/9] bus: mhi: Expose DDR training data via controller sysfs Kishore Batta
@ 2026-03-19 6:31 ` Kishore Batta
8 siblings, 0 replies; 11+ messages in thread
From: Kishore Batta @ 2026-03-19 6:31 UTC (permalink / raw)
To: Jonathan Corbet, Shuah Khan, Jeff Hugo, Carl Vanderlip,
Oded Gabbay, Manivannan Sadhasivam, andersson
Cc: linux-doc, linux-kernel, linux-arm-msm, dri-devel, mhi,
Kishore Batta
Add ABI documentation for the DDR training data sysfs attribute exposed by
the sahara MHI driver.
The documented sysfs node provides read-only access to the DDR training
data captured during sahara command mode and exposed via the MHI
controller device. This allows userspace to read the training data and
manage it as needed outside the kernel.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
.../ABI/testing/sysfs-bus-mhi-ddr_training_data | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-mhi-ddr_training_data b/Documentation/ABI/testing/sysfs-bus-mhi-ddr_training_data
new file mode 100644
index 0000000000000000000000000000000000000000..810b487b5a5fdba133d81255f9879844e3938a10
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-mhi-ddr_training_data
@@ -0,0 +1,19 @@
+What: /sys/bus/mhi/devices/<mhi-cntrl>/ddr_training_data
+
+Date: March 2026
+
+Contact: Kishore Batta <kishore.batta@oss.qualcomm.com>
+
+Description: Contains the DDR training data for the Qualcomm device
+ connected. MHI driver populates different controller
+ nodes for each device. The DDR training data is exposed
+ to userspace to read and save the training data file to
+ the filesystem. In the subsequent boot up of the device,
+ the training data is restored from host to device
+ optimizing the boot up time of the device.
+
+Usage: Example for reading DDR training data:
+ cat /sys/bus/mhi/devices/mhi0/ddr_training_data
+
+Permissions: The file permissions are set to 0444 allowing read
+ access.
--
2.34.1
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