linux-kernel - Re: [PATCH-v2 4/7] mmc: sdhci-pxav3: Add pinctl setting according to bus clock

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Message-ID: <CACRpkdY59roEBgUd9TR39yNgfhw393+WmHQQAeLkOEZLChOcWQ@mail.gmail.com>
Date:	Tue, 8 Sep 2015 16:42:38 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
Cc:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Kevin Liu <kliu5@...vell.com>
Subject: Re: [PATCH-v2 4/7] mmc: sdhci-pxav3: Add pinctl setting according to
 bus clock

On Mon, Sep 7, 2015 at 1:18 PM, Vaibhav Hiremath
<vaibhav.hiremath@...aro.org> wrote:

> Different bus clock may need different pin setting.
> For example, fast bus clock like 208Mhz need pin drive fast
> while slow bus clock prefer pin drive slow to guarantee
> signal quality.
>
> So this patch creates two states,
>   - Default (slow/normal) pin state
>   - And fast pin state for higher freq bus speed.
>
> And selection of pin state is done based on timing mode.
>
> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
> Signed-off-by: Kevin Liu <kliu5@...vell.com>
(...)
> +       pxa->pinctrl = devm_pinctrl_get(dev);
> +       if (!IS_ERR(pxa->pinctrl)) {
> +               pxa->pins_default = pinctrl_lookup_state(pxa->pinctrl, "default");
> +               if (IS_ERR(pxa->pins_default))
> +                       dev_err(dev, "could not get default pinstate\n");
> +               pxa->pins_fast = pinctrl_lookup_state(pxa->pinctrl, "fast");
> +               if (IS_ERR(pxa->pins_fast))
> +                       dev_info(dev, "could not get fast pinstate\n");
> +       }

This is exactly how I think it should be used from a pin control
point of view.

If you depended on CONFIG_PM you could use
pinctrl_pm_select_default_state() but for this simple scenario
this is fine.

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
>From a pinctrl point of view.

Yours,
Linus Walleij
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