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

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Hi Stefan,

On 09/27/2016 03:26 AM, Stefan Agner wrote:
> If a GPIO gets freed after selecting a new pinctrl configuration
> the driver should not change pinctrl anymore. Otherwise this will
> likely lead to a unusable pin configuration for > the newly selected
> pinctrl.
>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
> This turned out to be problematic when using the I2C GPIO bus recovery
>functionality. After muxing back to I2C, the GPIO is being freed, which
> cased I2C to stop working completely.

IMHO this recent "i.MX I2C GPIO bus recovery" feature is kind of a hack,
for example I believe it breaks I2C bus driver initialization on i.MX31
boards, where today there is no pinctrl driver at all.

IMHO something like I've partially described in the recent "Requesting as
a GPIO a pin already used through pinctrl" topic should be done here.
Could you consider to add another pinctrl-1 group with alternative GPIO
line mux/config settings to an i2c controller device node and apply it,
when you need a bus recovery? You may find references how this kind of
dynamic pinctrl management is done within mmc/sd subsystem.

By the way did I miss a patch, which falls back to mux settings on
.gpio_disable_free call for non-Vybrid platforms?

--
With best wishes,
Vladimir

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[PATCH] pinctrl: freescale: avoid overwriting pin config when freeing GPIO Stefan Agner <stefan@agner.ch> - 2016-09-27 02:30 +0200
  Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> - 2016-09-27 14:20 +0200
    Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Stefan Agner <stefan@agner.ch> - 2016-09-27 18:50 +0200
      Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> - 2016-09-27 20:20 +0200
        Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Stefan Agner <stefan@agner.ch> - 2016-09-27 21:50 +0200
          Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> - 2016-09-27 22:30 +0200
          Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Viresh Kumar <viresh.kumar@linaro.org> - 2016-09-28 04:10 +0200
            Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Stefan Agner <stefan@agner.ch> - 2016-09-28 05:50 +0200
              Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Viresh Kumar <viresh.kumar@linaro.org> - 2016-09-28 06:20 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Stefan Agner <stefan@agner.ch> - 2016-09-29 18:40 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Viresh Kumar <viresh.kumar@linaro.org> - 2016-09-30 04:20 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Linus Walleij <linus.walleij@linaro.org> - 2016-10-10 10:40 +0200
              Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> - 2016-09-28 14:10 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Viresh Kumar <viresh.kumar@linaro.org> - 2016-09-29 08:50 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> - 2016-09-29 14:20 +0200
                Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Viresh Kumar <viresh.kumar@linaro.org> - 2016-09-30 04:30 +0200
  Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when  freeing GPIO Linus Walleij <linus.walleij@linaro.org> - 2016-10-10 10:50 +0200

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