[PATCH 40/42] docs: scsi: convert ufs.txt to ReST

Mauro Carvalho Chehab
2020-03-02T08:17:11Z

Documentation/scsi/{ufs.txt => ufs.rst} | 84 ++++++++++++++++---------
MAINTAINERS | 2 +-
drivers/scsi/ufs/Kconfig | 2 +-
4 files changed, 57 insertions(+), 32 deletions(-)
rename Documentation/scsi/{ufs.txt => ufs.rst} (79%)

diff --git a/Documentation/scsi/index.rst b/Documentation/scsi/index.rst
index df005cb94f6b..27720d145eff 100644
--- a/Documentation/scsi/index.rst
+++ b/Documentation/scsi/index.rst
@@ -44,5 +44,6 @@ Linux SCSI Subsystem
sym53c500_cs
sym53c8xx_2
tcm_qla2xxx
+ ufs

scsi_transport_srp/figures
diff --git a/Documentation/scsi/ufs.txt b/Documentation/scsi/ufs.rst
similarity index 79%
rename from Documentation/scsi/ufs.txt
rename to Documentation/scsi/ufs.rst
index 81842ec3e116..a920c0a5a1f6 100644
--- a/Documentation/scsi/ufs.txt
+++ b/Documentation/scsi/ufs.rst
@@ -1,24 +1,26 @@
- Universal Flash Storage
- =======================
+.. SPDX-License-Identifier: GPL-2.0

+=======================
+Universal Flash Storage
+=======================

-Contents
---------

-1. Overview
-2. UFS Architecture Overview
- 2.1 Application Layer
- 2.2 UFS Transport Protocol(UTP) layer
- 2.3 UFS Interconnect(UIC) Layer
-3. UFSHCD Overview
- 3.1 UFS controller initialization
- 3.2 UTP Transfer requests
- 3.3 UFS error handling
- 3.4 SCSI Error handling
+.. Contents
+
+ 1. Overview
+ 2. UFS Architecture Overview
+ 2.1 Application Layer
+ 2.2 UFS Transport Protocol(UTP) layer
+ 2.3 UFS Interconnect(UIC) Layer
+ 3. UFSHCD Overview
+ 3.1 UFS controller initialization
+ 3.2 UTP Transfer requests
+ 3.3 UFS error handling
+ 3.4 SCSI Error handling

1. Overview
------------
+===========

Universal Flash Storage(UFS) is a storage specification for flash devices.
It is aimed to provide a universal storage interface for both
@@ -28,19 +30,25 @@ is defined by JEDEC Solid State Technology Association. UFS is based
on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
physical layer and MIPI Unipro as the link layer.

-The main goals of UFS is to provide,
+The main goals of UFS is to provide:
+
* Optimized performance:
- For UFS version 1.0 and 1.1 the target performance is as follows,
- Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
- Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
+
+ For UFS version 1.0 and 1.1 the target performance is as follows:
+
+ - Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
+ - Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
+
Future version of the standard,
- Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
+
+ - Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
+
* Low power consumption
* High random IOPs and low latency

2. UFS Architecture Overview
-----------------------------
+============================

UFS has a layered communication architecture which is based on SCSI
SAM-5 architectural model.
@@ -48,16 +56,22 @@ SAM-5 architectural model.
UFS communication architecture consists of following layers,

2.1 Application Layer
+---------------------

The Application layer is composed of UFS command set layer(UCS),
Task Manager and Device manager. The UFS interface is designed to be
protocol agnostic, however SCSI has been selected as a baseline
protocol for versions 1.0 and 1.1 of UFS protocol layer.
+
UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
- * UCS: It handles SCSI commands supported by UFS specification.
- * Task manager: It handles task management functions defined by the
+
+ * UCS:
+ It handles SCSI commands supported by UFS specification.
+ * Task manager:
+ It handles task management functions defined by the
UFS which are meant for command queue control.
- * Device manager: It handles device level operations and device
+ * Device manager:
+ It handles device level operations and device
configuration operations. Device level operations mainly involve
device power management operations and commands to Interconnect
layers. Device level configurations involve handling of query
@@ -65,10 +79,12 @@ UFS communication architecture consists of following layers,
information of the device.

2.2 UFS Transport Protocol(UTP) layer
+-------------------------------------

UTP layer provides services for
the higher layers through Service Access Points. UTP defines 3
service access points for higher layers.
+
* UDM_SAP: Device manager service access point is exposed to device
manager for device level operations. These device level operations
are done through query requests.
@@ -76,20 +92,23 @@ UFS communication architecture consists of following layers,
set layer(UCS) to transport commands.
* UTP_TM_SAP: Task management service access point is exposed to task
manager to transport task management functions.
+
UTP transports messages through UFS protocol information unit(UPIU).

2.3 UFS Interconnect(UIC) Layer
+-------------------------------

UIC is the lowest layer of UFS layered architecture. It handles
connection between UFS host and UFS device. UIC consists of
MIPI UniPro and MIPI M-PHY. UIC provides 2 service access points
to upper layer,
+
* UIC_SAP: To transport UPIU between UFS host and UFS device.
* UIO_SAP: To issue commands to Unipro layers.

3. UFSHCD Overview
-------------------
+==================

The UFS host controller driver is based on Linux SCSI Framework.
UFSHCD is a low level device driver which acts as an interface between
@@ -98,12 +117,14 @@ SCSI Midlayer and PCIe based UFS host controllers.
The current UFSHCD implementation supports following functionality,

3.1 UFS controller initialization
+---------------------------------

The initialization module brings UFS host controller to active state
and prepares the controller to transfer commands/response between
UFSHCD and UFS device.

3.2 UTP Transfer requests
+-------------------------

Transfer request handling module of UFSHCD receives SCSI commands
from SCSI Midlayer, forms UPIUs and issues the UPIUs to UFS Host
@@ -112,11 +133,13 @@ The current UFSHCD implementation supports following functionality,
of the status of the command.

3.3 UFS error handling
+----------------------

Error handling module handles Host controller fatal errors,
Device fatal errors and UIC interconnect layer related errors.

3.4 SCSI Error handling
+-----------------------

This is done through UFSHCD SCSI error handling routines registered
with SCSI Midlayer. Examples of some of the error handling commands
@@ -129,7 +152,7 @@ In this version of UFSHCD Query requests and power management
functionality are not implemented.

4. BSG Support
-------------------
+==============

This transport driver supports exchanging UFS protocol information units
(UPIUs) with a UFS device. Typically, user space will allocate
@@ -138,7 +161,7 @@ request_upiu and reply_upiu respectively. Filling those UPIUs should
be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.
*Caveat emptor*: The driver makes no further input validations and sends the
UPIU to the device as it is. Open the bsg device in /dev/ufs-bsg and
-send SG_IO with the applicable sg_io_v4:
+send SG_IO with the applicable sg_io_v4::

io_hdr_v4.guard = 'Q';
io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;
@@ -166,6 +189,7 @@ upiu-based protocol is available at:
For more detailed information about the tool and its supported
features, please see the tool's README.

-UFS Specifications can be found at,
-UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
-UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf
+UFS Specifications can be found at:
+
+- UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
+- UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf
diff --git a/MAINTAINERS b/MAINTAINERS
index a3bfe6813e5e..9ac2a10ca41f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17204,7 +17204,7 @@ R: Alim Akhtar <alim.akhtar@samsung.com>
R: Avri Altman <avri.altman@wdc.com>
L: linux-scsi@vger.kernel.org
S: Supported
-F: Documentation/scsi/ufs.txt
+F: Documentation/scsi/ufs.rst
F: drivers/scsi/ufs/

UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER DWC HOOKS
diff --git a/drivers/scsi/ufs/Kconfig b/drivers/scsi/ufs/Kconfig
index d14c2243e02a..e2005aeddc2d 100644
--- a/drivers/scsi/ufs/Kconfig
+++ b/drivers/scsi/ufs/Kconfig
@@ -46,7 +46,7 @@ config SCSI_UFSHCD
The module will be called ufshcd.

To compile this driver as a module, choose M here and read
- <file:Documentation/scsi/ufs.txt>.
+ <file:Documentation/scsi/ufs.rst>.
However, do not compile this as a module if your root file system
(the one containing the directory /) is located on a UFS device.

--
2.21.1