linux-kernel - Re: [RESEND PATCH] gpio: pcf857x: restore the initial line state of all pcf lines

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Date:	Tue, 31 May 2016 10:40:34 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	Sekhar Nori <nsekhar@...com>
Subject: Re: [RESEND PATCH] gpio: pcf857x: restore the initial line state of
 all pcf lines

On Fri, May 27, 2016 at 8:35 AM, Kishon Vijay Abraham I <kishon@...com> wrote:

> The reset values for all the PCF lines are high and hence on
> shutdown we should drive all the lines high in order to
> bring it to the reset state.
>
> This is actually required since PCF doesn't have a reset
> line and even after warm reset (by invoking "reboot" in
> prompt) the PCF lines maintains it's previous programmed
> state. This becomes a problem if the boards are designed to
> work with the default initial state.
>
> DRA7XX_evm uses PCF8575 and one of the PCF output lines
> feeds to MMC/SD VDD and this line should be driven high in order
> for the MMC/SD to be detected.  This line is modelled as
> regulator and the hsmmc driver takes care of enabling and
> disabling it. In the case of 'reboot', during shutdown path
> as part of it's cleanup process the hsmmc driver disables
> this regulator. This makes MMC *boot* not functional.
>
> Fix it by driving all the pcf lines high.
>
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> Signed-off-by: Sekhar Nori <nsekhar@...com>

Patch applied.

Yours,
Linus Walleij