linux-kernel - Re: [PATCH] pinctrl: rockchip: enable clock when reading pin direction register

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Date:   Wed, 20 Dec 2017 09:01:04 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>, linux-gpio@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH] pinctrl: rockchip: enable clock when reading pin
 direction register

On Tue, Dec 12, 2017 at 6:43 PM, Brian Norris <briannorris@...omium.org> wrote:

> We generally leave the GPIO clock disabled, unless an interrupt is
> requested or we're accessing IO registers. We forgot to do this for the
> ->get_direction() callback, which means we can sometimes [1] get
> incorrect results [2] from, e.g., /sys/kernel/debug/gpio.
>
> Enable the clock, so we get the right results!
>
> [1] Sometimes, because many systems have 1 or mor interrupt requested on
> each GPIO bank, so they always leave their clock on.
>
> [2] Incorrect, meaning the register returns 0, and so we interpret that
> as "input".
>
> Signed-off-by: Brian Norris <briannorris@...omium.org>

Patch applied with Heiko's review tag.

Yours,
Linus Walleij