linux-kernel - Re: [PATCH] drivers: firmware: xilinx: Add ZynqMP firmware driver

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Date:   Tue, 9 Jan 2018 14:40:06 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jolly Shah <jolly.shah@...inx.com>, ard.biesheuvel@...aro.org,
        mingo@...nel.org, gregkh@...uxfoundation.org,
        matt@...eblueprint.co.uk, hkallweit1@...il.com,
        keescook@...omium.org, dmitry.torokhov@...il.com,
        michal.simek@...inx.com
Cc:     Sudeep Holla <sudeep.holla@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jolly Shah <jollys@...inx.com>, Rajan Vaja <rajanv@...inx.com>
Subject: Re: [PATCH] drivers: firmware: xilinx: Add ZynqMP firmware driver



On 08/01/18 22:07, Jolly Shah wrote:
> This patch is adding communication layer with firmware.
> Firmware driver provides an interface to firmware APIs.
> Interface APIs can be used by any driver to communicate to
> PMUFW(Platform Management Unit). All requests go through ATF.
> Firmware-debug provides debugfs interface to all APIs.
> Firmware-ggs provides read/write interface to
> global storage registers.
> 
> Signed-off-by: Jolly Shah <jollys@...inx.com>
> Signed-off-by: Rajan Vaja <rajanv@...inx.com>
> ---
>  .../firmware/xilinx/xlnx,zynqmp-firmware.txt       |   16 +
>  arch/arm64/Kconfig.platforms                       |    1 +
>  drivers/firmware/Kconfig                           |    1 +
>  drivers/firmware/Makefile                          |    1 +
>  drivers/firmware/xilinx/Kconfig                    |    4 +
>  drivers/firmware/xilinx/Makefile                   |    4 +
>  drivers/firmware/xilinx/zynqmp/Kconfig             |   23 +
>  drivers/firmware/xilinx/zynqmp/Makefile            |    5 +
>  drivers/firmware/xilinx/zynqmp/firmware-debug.c    |  540 +++++++++++
>  drivers/firmware/xilinx/zynqmp/firmware-ggs.c      |  298 ++++++
>  drivers/firmware/xilinx/zynqmp/firmware.c          | 1024 ++++++++++++++++++++
>  .../linux/firmware/xilinx/zynqmp/firmware-debug.h  |   32 +
>  include/linux/firmware/xilinx/zynqmp/firmware.h    |  573 +++++++++++
>  13 files changed, 2522 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.txt
>  create mode 100644 drivers/firmware/xilinx/Kconfig
>  create mode 100644 drivers/firmware/xilinx/Makefile
>  create mode 100644 drivers/firmware/xilinx/zynqmp/Kconfig
>  create mode 100644 drivers/firmware/xilinx/zynqmp/Makefile
>  create mode 100644 drivers/firmware/xilinx/zynqmp/firmware-debug.c
>  create mode 100644 drivers/firmware/xilinx/zynqmp/firmware-ggs.c
>  create mode 100644 drivers/firmware/xilinx/zynqmp/firmware.c
>  create mode 100644 include/linux/firmware/xilinx/zynqmp/firmware-debug.h
>  create mode 100644 include/linux/firmware/xilinx/zynqmp/firmware.h
> 
> diff --git a/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.txt b/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.txt
> new file mode 100644
> index 0000000..ace111c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.txt
> @@ -0,0 +1,16 @@
> +Xilinx Zynq MPSoC Firmware Device Tree Bindings
> +
> +The zynqmp-firmware node describes the interface to platform firmware.
> +
> +Required properties:
> + - compatible:	Must contain:  "xlnx,zynqmp-firmware"
> + - method:	The method of calling the PM-API firmware layer.
> +		Permitted values are:
> +		 - "smc" : To be used in configurations without a hypervisor
> +		 - "hvc" : To be used when hypervisor is present
> +

If we are having a mailbox using smc/hvc, then it can be made generic
rather than xilinx specific. I can see other user of the same. As Jassi
pointed out in some other thread, Andre has some generic implementation.
Please see how it can be reused.

Also please keep any bindings separate from the driver changes so that
it can be reviewed separately.

> +Examples:
> +	firmware: firmware {
> +		compatible = "xlnx,zynqmp-firmware";
> +		method = "smc";

Ideally this should point to mailbox if we move to using smc/hvc based
mailbox.

[...]

> +
> +config ZYNQMP_FIRMWARE_DEBUG
> +	bool "Enable Xilinx Zynq MPSoC firmware debug APIs"
> +	depends on ARCH_ZYNQMP && DEBUG_FS

Do you need a separate Kconfig option, can't you just use DEBUG_FS ?

[...]

> +
> +	if (strncasecmp(pm_api_req, "REQUEST_SUSPEND", 15) == 0)
> +		pm_id = REQUEST_SUSPEND;
> +	else if (strncasecmp(pm_api_req, "SELF_SUSPEND", 12) == 0)
> +		pm_id = SELF_SUSPEND;
> +	else if (strncasecmp(pm_api_req, "FORCE_POWERDOWN", 15) == 0)
> +		pm_id = FORCE_POWERDOWN;
> +	else if (strncasecmp(pm_api_req, "ABORT_SUSPEND", 13) == 0)
> +		pm_id = ABORT_SUSPEND;


Can this be changed to a loop with a static structure array containing
{pm_id, pm_string, strlen(pm_string)} ?

Also I see hard-coded string length is wrong in some cases like IOCTL.
Isn't it better to just use strlen("..") instead ?

I will stop here as the patch can be easily split and several features
can be added incrementally making the base patch simpler and shorter.

-- 
Regards,
Sudeep