[RFC 0/6] firmware: scmi: add SCMI pinctrl protocol support

[Fabio Estevam]

Adding Peng Fan, who is working on scmi/pinctrl support for i.MX9:

https://lore.kernel.org/all/ZO9GLG5tQynYyAvR@pluto/T/

On Tue, Sep 5, 2023 at 11:41 PM AKASHI Takahiro
<takahiro.akashi at linaro.org> wrote:
>
> This is an RFC and meant to get feedback from other developers as
> - the specification (pinctrl part) is still in a draft
> - the upstream patch for linux, including dt bindings, is still WIP
> - I'm not confident the drivers are generic enough to cover most HWs
> - The tests ("ut") doesn't cover all the features yet
>
>
> This patch series allows users to access SCMI pin control protocol provided
> by SCMI server (platform). See SCMI specification document v3.2 beta 2[1]
> for more details about SCMI pin control protocol.
>
> The implementation consists of two layers:
> - basic helper functions for SCMI pin control protocol
>   in drivers/firmware/scmi/pinctrl.c (patch#2)
> - DM-compliant pinctrl/gpio drivers, which utilizes the helper functions,
>   in drivers/pinctrl/pinctrl-scmi.c (patch#3,#4)
>
> [1] https://developer.arm.com/documentation/den0056/e/?lang=en
>
> DT bindings
> ===========
> Upstream pinctrl patch for linux defines the bindings in [2] though
> it doesn't say much.
> I expect that my implementation basically complies with U-Boot's generic
> bindings described in [3], but not all the features are verified.
>
> As for gpio, unless you hard-code pin assignments directly in a device
> driver, my implementation allows the following alternatives in DT.
> Either way, we may need an additional binding description for gpio.
>
> (A)
>     scmi {
>         ... // other protocols
>         scmi_pinctrl: protocol at 19 { // Pin control protocol
>             ...
>             {pinmux definitions}... // if any, including GPIO?
>         }
>     }
>     scmi_gpio: scmi_gpio {
>         compatible = "arm,scmi-gpio-generic";
>         gpio-controller;
>         #gpio-cells = <2>;
>         gpio-ranges = <&scmi_pinctrl 0 5 4>,
>                       <&scmi_pinctrl 4 0 0>;
>         gpio-ranges-group-names = "",
>                                   "ANOTHER_GPIO_GROUP";
>     }
>     some_device {
>         ...
>         reset-gpios = <&scmi_gpio 0 GPIO_ACTIVE_HIGH>;
>     }
> (B)
>     scmi {
>         ... // other protocols
>         scmi_pinctrl: protocol at 19 { // Pin control protocol
>             ...
>             {pinmux definitions}... // if any, including GPIO?
>
>             scmi_gpio: scmi_gpio {
>                 // no need for "compatible"
>                 gpio-controller;
>                 #gpio-cells = <2>;
>                 gpio-ranges = <&scmi_pinctrl 0 5 4>,
>                               <&scmi_pinctrl 4 0 0>;
>                 gpio-ranges-group-names = "",
>                                           "ANOTHER_GPIO_GROUP";
>             }
>         }
>     }
>     some_device {
>         ...
>         reset-gpios = <&scmi_gpio 0 GPIO_ACTIVE_HIGH>;
>     }
> (C)
>     if "gpio-ranges" is missing in gpio definition, assume 1:1 mapping,
>     i.e. use a native pinctrl pin number (5).
>     some_device {
>         ...
>         reset-gpios = <&scmi_gpio 5 GPIO_ACTIVE_HIGH>;
>     }
>
>
> [2] https://lkml.iu.edu/hypermail/linux/kernel/2308.1/01084.html
> [3] <u-boot>/doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt
>     <u-boot>/doc/device-tree-bindings/gpio/gpio.txt
>
> Test
> ====
> The patch series was tested on the following platforms:
> * sandbox ("ut dm pinmux" and manually using gpio command)
>
>
> Prerequisite:
> =============
> * This patch series is based on my WIP "Base protocol support" patches
>   on v2023.10-rc3. You can fetch the whole code from [4].
>
> [4] https://git.linaro.org/people/takahiro.akashi/u-boot.git
>     branch:scmi/pinctrl
>
>
> Patches:
> ========
> Patch#1: Add SCMI base protocol driver
> Patch#2-#4: Add drivers
> Patch#5-#6: Test related
>
>
> Change history:
> ===============
> RFC (Sep 6, 2023)
> * initial release as RFC
>
> AKASHI Takahiro (6):
>   firmware: scmi: fix protocol enumeration logic
>   firmware: scmi: add pinctrl protocol support
>   pinctrl: add scmi driver
>   gpio: add scmi driver based on pinctrl
>   firmware: scmi: add pseudo pinctrl protocol support on sandbox
>   test: dm: add SCMI pinctrl test
>
>  arch/sandbox/dts/test.dts                  |  115 +++
>  cmd/scmi.c                                 |    1 +
>  drivers/firmware/scmi/Kconfig              |    3 +
>  drivers/firmware/scmi/Makefile             |    1 +
>  drivers/firmware/scmi/pinctrl.c            |  412 ++++++++
>  drivers/firmware/scmi/sandbox-scmi_agent.c |  722 +++++++++++++
>  drivers/firmware/scmi/scmi_agent-uclass.c  |   18 +-
>  drivers/pinctrl/Kconfig                    |   11 +
>  drivers/pinctrl/Makefile                   |    1 +
>  drivers/pinctrl/pinctrl-scmi.c             | 1071 ++++++++++++++++++++
>  include/scmi_agent-uclass.h                |    2 +
>  include/scmi_protocols.h                   |  435 ++++++++
>  test/dm/scmi.c                             |   62 ++
>  13 files changed, 2852 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/firmware/scmi/pinctrl.c
>  create mode 100644 drivers/pinctrl/pinctrl-scmi.c
>
> --
> 2.34.1
>