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

[AKASHI Takahiro]

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