linux-kernel - Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when freeing GPIO

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Date:   Wed, 28 Sep 2016 09:44:51 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        linus.walleij@...aro.org, shawnguo@...nel.org,
        aalonso@...escale.com, b38343@...escale.com, ldewangan@...dia.com,
        van.freenix@...il.com, p.zabel@...gutronix.de,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when
 freeing GPIO

On 27-09-16, 20:38, Stefan Agner wrote:
> The i.MX I2C driver touches the pinctrl in its prepare/unprepare
> callbacks.
> 
> So, on a i.MX or Vybrid, the call chain looks like this:
> 
> i2c_generic_gpio_recovery
>     -> i2c_get_gpios_for_recovery
>        -> gpio_request_one
>     -> i2c_generic_recovery
>        -> prepare_recovery (i2c_imx_prepare_recovery)
>           -> pinctrl_select_state [gpio]

Why is this done here? And not in gpio_request_one?

>        -> unprepare_recovery (i2c_imx_unprepare_recovery)
>           -> pinctrl_select_state [default]
>     -> i2c_put_gpios_for_recovery
>        -> gpio_free
> 
> 
> And for the pinctrl/GPIO driver of Vybrid this is actually a problem
> because gpio_free disables the output driver of the pad, and when that
> happens after the (I2C) default pinctrl state gets selected the pad is
> no longer active.
> 
> --
> Stefan

-- 
viresh