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Gmane
From: =?UTF-8?q?Sjur=20Br=C3=A6ndeland?= <sjur.brandeland <at> stericsson.com>
Subject: [RFCv1 0/9] XSHM: Shared Memory Driver for ST-E Thor M7400 LTE modem
Newsgroups: gmane.linux.kernel
Date: Monday 21st November 2011 13:55:55 UTC (over 5 years ago)
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 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 conntent) 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 proveded 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. For each fixed-size buffer the channel has a read and
write pointer 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
~~~~~~~~~~~~~~
Current implementation is using the platform bus, but I' currently
investigating migrating to Virtio (suggested by Linus Walleij).

Review comments and feedback is welcome.

Regards,
Sjur Brændeland

Sjur Brændeland (9):
  xshm: Shared Memory layout for ST-E M7400 driver.
  xshm: Channel config definitions for ST-E M7400 driver.
  xshm: Config data use for platform devices.
  xshm: geni/geno driver interface.
  xshm: genio dummy driver
  xshm: Platform driver for XSHM
  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      |  900 ++++++++++++++++++++++++++
 drivers/xshm/Kconfig              |   10 +
 drivers/xshm/Makefile             |    4 +
 drivers/xshm/genio_dummy.c        |   61 ++
 drivers/xshm/xshm_boot.c          | 1176
++++++++++++++++++++++++++++++++++
 drivers/xshm/xshm_chr.c           | 1258
+++++++++++++++++++++++++++++++++++++
 drivers/xshm/xshm_pdev.c          |  459 ++++++++++++++
 include/linux/xshm/genio.h        |  195 ++++++
 include/linux/xshm/xshm_ipctoc.h  |  160 +++++
 include/linux/xshm/xshm_netlink.h |   94 +++
 include/linux/xshm/xshm_pdev.h    |  188 ++++++
 15 files changed, 4519 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/genio_dummy.c
 create mode 100644 drivers/xshm/xshm_boot.c
 create mode 100644 drivers/xshm/xshm_chr.c
 create mode 100644 drivers/xshm/xshm_pdev.c
 create mode 100644 include/linux/xshm/genio.h
 create mode 100644 include/linux/xshm/xshm_ipctoc.h
 create mode 100644 include/linux/xshm/xshm_netlink.h
 create mode 100644 include/linux/xshm/xshm_pdev.h
 
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