linux-kernel - Re: [PATCH 16/22] xlink-ipc: Add xlink ipc driver

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Date:   Mon, 7 Dec 2020 11:53:58 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     mgross@...ux.intel.com, markgross@...nel.org, arnd@...db.de,
        bp@...e.de, damien.lemoal@....com, dragan.cvetic@...inx.com,
        gregkh@...uxfoundation.org, corbet@....net,
        leonard.crestez@....com, palmerdabbelt@...gle.com,
        paul.walmsley@...ive.com, peng.fan@....com, robh+dt@...nel.org,
        shawnguo@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Seamus Kelly <seamus.kelly@...el.com>,
        linux-doc@...r.kernel.org,
        Ryan Carnaghi <ryan.r.carnaghi@...el.com>
Subject: Re: [PATCH 16/22] xlink-ipc: Add xlink ipc driver

Ahoy--

On 12/1/20 2:35 PM, mgross@...ux.intel.com wrote:
> From: Seamus Kelly <seamus.kelly@...el.com>
> 
> Add xLink driver, which interfaces the xLink Core driver with the Keem
> Bay VPU IPC driver, thus enabling xLink to control and communicate with
> the VPU IP present on the Intel Keem Bay SoC.
> 
> Specifically the driver enables xLink Core to:
> 
> * Boot / Reset the VPU IP
> * Register to VPU IP event notifications (device connected, device
>   disconnected, WDT event)
> * Query the status of the VPU IP (OFF, BUSY, READY, ERROR, RECOVERY)
> * Exchange data with the VPU IP, using the Keem Bay IPC mechanism
>   - Including the ability to send 'volatile' data (i.e., small amount of
>     data, up to 128-bytes that was not allocated in the CPU/VPU shared
>     memory region)
> 
> Cc: linux-doc@...r.kernel.org
> Reviewed-by: Mark Gross <mgross@...ux.intel.com>
> Signed-off-by: Seamus Kelly <seamus.kelly@...el.com>
> Signed-off-by: Ryan Carnaghi <ryan.r.carnaghi@...el.com>
> ---
>  Documentation/vpu/index.rst        |   1 +
>  Documentation/vpu/xlink-ipc.rst    |  50 ++
>  MAINTAINERS                        |   6 +
>  drivers/misc/Kconfig               |   1 +
>  drivers/misc/Makefile              |   1 +
>  drivers/misc/xlink-ipc/Kconfig     |   7 +
>  drivers/misc/xlink-ipc/Makefile    |   4 +
>  drivers/misc/xlink-ipc/xlink-ipc.c | 879 +++++++++++++++++++++++++++++
>  include/linux/xlink-ipc.h          |  48 ++
>  9 files changed, 997 insertions(+)
>  create mode 100644 Documentation/vpu/xlink-ipc.rst
>  create mode 100644 drivers/misc/xlink-ipc/Kconfig
>  create mode 100644 drivers/misc/xlink-ipc/Makefile
>  create mode 100644 drivers/misc/xlink-ipc/xlink-ipc.c
>  create mode 100644 include/linux/xlink-ipc.h

> diff --git a/Documentation/vpu/xlink-ipc.rst b/Documentation/vpu/xlink-ipc.rst
> new file mode 100644
> index 000000000000..af583579e70d
> --- /dev/null
> +++ b/Documentation/vpu/xlink-ipc.rst
> @@ -0,0 +1,50 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +Kernel driver: xLink IPC driver
> +=================================
> +Supported chips:
> +
> +* | Intel Edge.AI Computer Vision platforms: Keem Bay
> +  | Suffix: Bay
> +  | Datasheet: (not yet publicly available)
> +
> +------------
> +Introduction
> +------------
> +
> +The xLink IPC driver interfaces the xLink Core driver with the Keem Bay VPU IPC
> +driver, thus enabling xLink to control and communicate with the VPU IP present
> +on the Intel Keem Bay SoC.
> +
> +Specifically the driver enables xLink Core to:
> +
> +* Boot / Reset the VPU IP
> +* Register to VPU IP event notifications (device connected, device disconnected,
> +  WDT event)
> +* Query the status of the VPU IP (OFF, BUSY, READY, ERROR, RECOVERY)
> +* Exchange data with the VPU IP, using the Keem Bay IPC mechanism
> +
> +  * Including the ability to send 'volatile' data (i.e., small amount of data,
> +    up to 128-bytes that was not allocated in the CPU/VPU shared memory region)
> +
> +Sending / Receiving 'volatile' data
> +-----------------------------------
> +
> +Data to be exchanged with Keem Bay IPC needs to be allocated in the portion of
> +DDR shared between the CPU and VPU.
> +
> +This can be impractical for small amount of data that user code can allocate

                                     amounts

> +on the stack.
> +
> +To reduce the burden on user code, xLink Core provides special send / receive
> +functions to send up to 128 bytes of 'volatile data', i.e., data that is not
> +allocated in the shared memory and that might also disappear after the xLink
> +API is called (e.g., because allocated on the stack).
> +
> +The xLink IPC driver implements support for transferring such 'volatile data'
> +to the VPU using Keem Bay IPC. To this end, the driver reserved some memory in

better:                                                   reserves

> +the shared memory region.
> +
> +When volatile data is to be sent, xLink IPC allocates a buffer from the
> +reserved memory region and copies the volatile data to the buffer. The buffer
> +is then transferred to the VPU using Keem Bay IPC.

> diff --git a/drivers/misc/xlink-ipc/Kconfig b/drivers/misc/xlink-ipc/Kconfig
> new file mode 100644
> index 000000000000..6aa2592fe9a3
> --- /dev/null
> +++ b/drivers/misc/xlink-ipc/Kconfig
> @@ -0,0 +1,7 @@
> +config XLINK_IPC
> +	tristate "Support for XLINK IPC"
> +	depends on KEEMBAY_VPU_IPC
> +	help
> +	  XLINK IPC enables the communication/control IPC Sub-System.
> +
> +	  Select M if you have an Intel SoC with a Vision Processing Unit (VPU)

End that sentence with a '.', please.


-- 
~Randy