linux-kernel - Re: [PATCH 2/3] ARM: OMAP1: ams-delta: initialize latch2 pins to safe values

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Date:   Thu, 23 Aug 2018 12:44:06 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Janusz Krzysztofik <jmkrzyszt@...il.com>
Cc:     ext Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        linux-serial@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] ARM: OMAP1: ams-delta: initialize latch2 pins to safe values

On Mon, Aug 20, 2018 at 8:12 PM Janusz Krzysztofik <jmkrzyszt@...il.com> wrote:

> Latch2 pins control a number of on-board devices, namely LCD, NAND,
> MODEM and CODEC.  Those pins used to be initialized with safe values
> from init_machine before that operation was:
> 1) moved to late_initcall in preparation for conversion of latch2 to
> GPIO device - see commit f7519d8c8290 ("ARM: OMAP1: ams-delta: register
> latch dependent devices later"),
> 2) replaced with non-atomic initialization performed by means of
> gpio_request_array() - see commit 937eb4bb0058 ("ARM: OMAP1: ams-delta:
> convert latches to basic_mmio_gpio"),
> 3) made completely asynchronous by delegation of GPIO request
> operations performed on subsets of pins to respective device drivers in
> subsequent commits.
>
> One visible negative result of that disintegration was corrupt keyboard
> data reported by serio driver, recently fixed by commit 41f8fee385a0
> ("ARM: OMAP1: ams-delta: Hog "keybrd_dataout" GPIO pin").
>
> Moreover, initialization of LATCH2_PIN_MODEM_CODEC still performed with
> ams_delta_latch2_write() wrapper from late_init() is now done on not
> requested GPIO pin.
>
> Reintroduce atomic initialization of latch2 pins at machine_init to
> prevent from random values potentially corrupting NAND data or maybe
> even destroing other hardware.  Also take care of MODEM/CODEC related
> pins so MODEM device probe succeeds even if latch2 GPIO device or
> dependent regulator is not ready and CODEC can be reached over the
> MODEM even if audio driver doesn't take control over
> LATCH2_PIN_MODEM_CODEC.
>
> Once done, remove the no longer needed GPIO based implementation of
> ams_delta_latch_write() and its frontend macro.
>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>

This should turn into a nice pin control driver some day.

But until then, this looks way better after than before the patch,
so:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij