linux-kernel - Re: [RFC v1 1/2] scmi: Introduce pinctrl SCMI protocol driver

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Message-ID: <CACRpkdY1eSdWX6+azn43MO77urVf_t25wgZtuyTwKHw4v+QYNg@mail.gmail.com>
Date:   Fri, 21 Apr 2023 11:28:38 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Oleksii Moisieiev <Oleksii_Moisieiev@...m.com>
Cc:     Peng Fan <peng.fan@....nxp.com>,
        Cristian Marussi <cristian.marussi@....com>,
        "sudeep.holla@....com" <sudeep.holla@....com>,
        "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>,
        "michal.simek@....com" <michal.simek@....com>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "souvik.chakravarty@....com" <souvik.chakravarty@....com>
Subject: Re: [RFC v1 1/2] scmi: Introduce pinctrl SCMI protocol driver

On Fri, Apr 21, 2023 at 10:40 AM Oleksii Moisieiev
<Oleksii_Moisieiev@...m.com> wrote:
> On 17.04.23 05:55, Peng Fan wrote:
> > On 4/13/2023 6:04 AM, Cristian Marussi wrote:

> > Is it possible to extend the spec to support multilple uint32_t for PIN
> > CONFIG SET?
> >
> > With only one uint32_t could not satisfy i.MX requirement.
> >
> > Thanks,
> > Peng.
> >
> IIUC you are expecting to have an ability to set some kind of array of
> uint32_t config values to some specific ConfigType?
>
> I'm not sure if it's supported by pintctrl subsystem right now. I was
> unable to find an example in the existing device-tree pinctrl bindings.
> This makes me think that this kind of binding is OEM specific.
>
> Maybe it can be implemented by adding new IDs to OEM specific range
> (192-255) which is reserved for OEM specific units (See Table 23 of
> DEN0056E).

>From a pinctrl point of view I do not understand this requirement.

The pinctrl subsystem in the Linux kernel certainly does not support
an array of u32 for the pin config, we only support passing a single
u32 value along with the enumerator (config type), or well it is
actually 24 bits in Linux, the uppermost 8 bits is for the config type:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/pinctrl/pinconf-generic.h

/*
 * Helpful configuration macro to be used in tables etc.
 */
#define PIN_CONF_PACKED(p, a) ((a << 8) | ((unsigned long) p & 0xffUL))

p = parameter (PIN_CONFIG_DRIVE_STRENGTH etc)
a = argument (value such as in mA)

Yours,
Linus Walleij