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Subject[RFCv1 0/9] XSHM: Shared Memory Driver for ST-E Thor M7400 LTE modem
Date
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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