[PATCHv2 00/10] XSHM: Shared Memory Driver for ST-E Thor M7400 LTE modem

Sjur Brændeland
2011-12-09T14:07:43Z

Changes since PATCHv2:
~~~~~~~~~~~~~~~~~~~~~~
o Added XSHM bus framework in xshm_bus.c.
o Use XSHM devices instead of platform devices.
o Restructured xshm_dev.c and xshm_boot.c as separate modules.
o Renamed xshm_pdev.h to xshm_dev.h
o Avoid keeping a list of devices, bus-iterator is used instead.
o Updated Kconfig as separate menu, and a CONFIG_* for each module.
o Included fixes and review comments from Dan Carpenter:
xshm: release misc device on error
xshm: calling unlock improperly in xshmchr_poll()

Introduction:
~~~~~~~~~~~~~
This patch-set introduces the Shared Memory Driver for ST-Ericsson's
Thor M7400 LTE modem.
The shared memory model is implemented for Chip-to-chip and
uses a reserved memory area and a number of bi-directional
channels. Each channel has it's own designated data area where payload
data is copied into.

Two different channel types are defined, one stream channel which is
implemented as a traditional ring-buffer, and a packet channel which
is a ring-buffer of fix sized buffers where each buffer contains
an array of CAIF frames.

The notification of read and write index updates are handled in a
separate driver called c2c_genio. This driver will be contributed separately,
but the API is included in this patch-set.

The channel configuration is stored in shared memory, each channel
has a designated area in shared memory for configuration data,
read and write indexes and a data area.

Configuration
~~~~~~~~~~~~~~~

IPC-TOC
+--------------------+ Index Area
| Channel Descr 0 | -----> +------------+
| | -+ | Read Index |
|--------------------| | |------------|
| Channel Descr 1 | | | Write Index|
| | | +------------+
|--------------------| | Data Area
| ... | | +------------+
| | +---> | |
+--------------------+ | |
| |
+------------+

A IPC-TOC (table of content) is used for holding configuration data
for the channels (struct xshm_ipctoc). It contains an array of
channel descriptors (struct xshm_ipctoc_channel). The channel
descriptors points out the data area and the location of
read and write indexes.

The configuration is provided from user-space using gen-netlink.
The gen-netlink format is defined in xshm_netlink.h and and handled
in xshm_boot.c

Packet data
~~~~~~~~~~~
The packet channel is set up to minimize interrupts needed to
transfer a packet and to allow efficient DMA operations on the modem.

Ring Buffer Indexes:
+------------+
+-| Read Index |
| |------------|
| | Write Index|------------------------+
| +------------+ |
| |
V |
Buffer-0: V Buffer-1:
+----------------------------------------+---------------+---
|ofs,len|ofs,len| ....| frm-0|frm-1| ... | ofs,len | ....|...
+----------------------------------------+---------------+--
| | ^ ^
+---------------------+ |
+---------------------+

Packet data is organized in a channel containing a number of fixed-
size buffers. The channel has a read and write pointer to a buffer in a normal
ring-buffer fashion.

Each buffer holds an array of CAIF-frames, and starts with an descriptor array
containing pointers to the data frames in the buffer. The descriptor array
contains offset and length of each frame.

The packet device (caif_xshm.c) is implemented as a network interface of
type ARPHRD_CAIF.

Stream data
~~~~~~~~~~~
The driver for the stream channel is implemented as a character device
interface to user space. The character device implements non-blocking open
and non-blocking IO in general. The character device is implementing
a traditional circular buffer directly in the shared memory region for
the channel.

Driver model
~~~~~~~~~~~~~~
A XSHM bus is implemented, the example below show caif packet device, and
one stream device:

/sys/bus/xshm
|-- devices
| |-- xshm0 -> ../../../devices/xshm/xshm0
| `-- xshm1 -> ../../../devices/xshm/xshm1
|-- drivers
| `-- xshm_chr
| |-- bind
| |-- module -> ../../../../module/xshm_chr
| |-- uevent
| |-- unbind
| `-- xshm0 -> ../../../../devices/xshm/xshm0
|-- drivers_autoprobe
|-- drivers_probe
`-- uevent

/sys/devices/xshm/
|-- bootimg
|-- caif_ready
|-- ipc_ready
|-- uevent
|-- xshm0
| |-- driver -> ../../../bus/xshm/drivers/xshm_chr
| |-- misc
| | `-- xshm0
| | |-- dev
| | |-- device -> ../../../xshm0
| | |-- subsystem -> ../../../../../class/misc
| | `-- uevent
| |-- subsystem -> ../../../bus/xshm
| `-- uevent
`-- xshm1
|-- subsystem -> ../../../bus/xshm
`-- uevent

Review comments and feedback is welcome.

Regards,
Sjur Brændeland

Sjur Brændeland (10):
xshm: Shared Memory layout for ST-E M7400 driver.
xshm: Channel config definitions for ST-E M7400 driver.
xshm: Configuration for XSHM Channel an devices.
xshm: geni/geno driver interface.
xshm: genio dummy driver
xshm: Add xshm device implementation
xshm: XSHM Configuration data handling
xshm: Character device for XSHM channel access.
xshm: Makefile and Kconfig for M7400 Shared Memory Drivers
caif-xshm: Add CAIF driver for Shared memory for M7400

drivers/Kconfig | 2 +
drivers/Makefile | 1 +
drivers/net/caif/Kconfig | 10 +
drivers/net/caif/Makefile | 1 +
drivers/net/caif/caif_xshm.c | 930 +++++++++++++++++++++++++++
drivers/xshm/Kconfig | 60 ++
drivers/xshm/Makefile | 5 +
drivers/xshm/dummy_c2c_genio.c | 76 +++
drivers/xshm/xshm_boot.c | 1116 ++++++++++++++++++++++++++++++++
drivers/xshm/xshm_chr.c | 1268 +++++++++++++++++++++++++++++++++++++
drivers/xshm/xshm_dev.c | 526 +++++++++++++++
include/linux/Kbuild | 1 +
include/linux/c2c_genio.h | 195 ++++++
include/linux/xshm/Kbuild | 1 +
include/linux/xshm/xshm_dev.h | 250 ++++++++
include/linux/xshm/xshm_ipctoc.h | 160 +++++
include/linux/xshm/xshm_netlink.h | 95 +++
17 files changed, 4697 insertions(+), 0 deletions(-)
create mode 100644 drivers/net/caif/caif_xshm.c
create mode 100644 drivers/xshm/Kconfig
create mode 100644 drivers/xshm/Makefile
create mode 100644 drivers/xshm/dummy_c2c_genio.c
create mode 100644 drivers/xshm/xshm_boot.c
create mode 100644 drivers/xshm/xshm_chr.c
create mode 100644 drivers/xshm/xshm_dev.c
create mode 100644 include/linux/c2c_genio.h
create mode 100644 include/linux/xshm/Kbuild
create mode 100644 include/linux/xshm/xshm_dev.h
create mode 100644 include/linux/xshm/xshm_ipctoc.h
create mode 100644 include/linux/xshm/xshm_netlink.h