linux-kernel - Re: [RFC v1 0/2] Introducing generic SCMI pinctrl driver implementation

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Message-ID: <905bd588-38c7-e3ad-c201-534c4593aa51@amd.com>
Date:   Wed, 26 Apr 2023 14:06:05 +0200
From:   Michal Simek <michal.simek@....com>
To:     Oleksii Moisieiev <Oleksii_Moisieiev@...m.com>,
        "sudeep.holla@....com" <sudeep.holla@....com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [RFC v1 0/2] Introducing generic SCMI pinctrl driver
 implementation

Hi,

On 4/7/23 12:18, Oleksii Moisieiev wrote:
> This RFC patch series is intended to introduce the potential generic driver for
> pin controls over SCMI protocol, provided in the latest beta version of DEN0056 [0].
> 
> On ARM-based systems, a separate Cortex-M based System Control Processor (SCP)
> provides control on pins, as well as with power, clocks, reset controllers. In this case,
> kernel should use one of the possible transports, described in [0] to access SCP and
> control clocks/power-domains etc. This driver is using SMC transport to communicate with SCP via
> SCMI protocol and access to the Pin Control Subsystem.
> 
> The provided driver consists of 2 parts:
>   - firmware/arm_scmi/pinctrl.c - the SCMI pinctrl protocol inmplementation
>     responsible for the communication with SCP firmware.
> 
>   - drivers/pinctrl/pinctrl-scmi.c - pinctrl driver, which is using pinctrl
>    protocol implementation to access all necessary data.
> 
> Configuration:
> The scmi-pinctrl driver can be configured using DT bindings.
> For example:
> / {
> 	cpu_scp_shm: scp-shmem@...3FF0000 {
> 		compatible = "arm,scmi-shmem";
> 		reg = <0x0 0x53FF0000 0x0 0x1000>;
> 	};
> 
> 	firmware {
> 		scmi {
> 			compatible = "arm,scmi-smc";
> 			arm,smc-id = <0x82000002>;
> 			shmem = <&cpu_scp_shm>;
> 			#address-cells = <1>;
> 			#size-cells = <0>;
> 
> 			scmi_pinctrl: protocol@19 {
> 				reg = <0x18>;
> 				#pinctrl-cells = <0>;
> 
> 				i2c2_pins: i2c2 {
> 					groups = "i2c2_a";
> 					function = "i2c2";
> 				};
> 			};
> 		};
> 	};
> };

Spec itself has as the part of pinctrl also gpio support.
Here the example there is no gpio-cells property that's why I am curious if you 
plan to also add it here.

Thanks,
Michal