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@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@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@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