linux-kernel - Re: [PATCH] ARM: tegra: Comment out gpio-ranges properties

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Message-ID: <5210588.IYgZy3yWn7@wuerfel>
Date:	Thu, 15 Oct 2015 17:59:08 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Thierry Reding <thierry.reding@...il.com>, arm@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: tegra: Comment out gpio-ranges properties

On Friday 09 October 2015 17:51:47 Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> While the addition of these properties is technically correct it unveils
> a bug with deferred probe. The problem is that the presence of the gpio-
> range property causes the gpio-tegra driver to defer probe (it needs the
> pinctrl driver to be ready). That's technically correct, but it causes a
> couple of issues:
> 
>   - The keyboard on Chromebooks stops working. The reason for that is
>     that the gpio-tegra device has not registered an IRQ domain by the
>     time the EC SPI device is registered, hence the interrupt number
>     resolves to 0. This is technically a bug in the SPI core, since it
>     should really resolve the interrupt at probe time and defer if the
>     IRQ domain isn't available yet. This is similar to what's done for
>     I2C and platform device already.
> 
>   - The gpio-tegra device deferring probe means that it is moved to the
>     end of the dpm_list. This list defines the suspend/resume order for
>     devices. However the core lacks a way to move all users of the
>     gpio-tegra device to the end of the dpm_list at the same time. This
>     in turn results in a subtle bug on Jetson TK1, where the gpio-keys
>     device is used to expose the power key as input. The power key is a
>     convenient way to wake the system from suspend. Interestingly, the
>     gpio-keys device ends up getting probed at a point after gpio-tegra
>     has been probed successfully from having been deferred earlier. As
>     such the driver doesn't need to defer the probe itself, and hence
>     the device isn't moved to the end of the dpm_list. This causes the
>     gpio-tegra device to be suspended before gpio-keys, which in turn
>     leaves gpio-keys unable to wake the system from suspend.
> 
> There are patches in the works to fix both of the above issues, but they
> are too involved to make it into v4.3, so in the meantime let's fix the
> regressions by commenting out the gpio-ranges properties until the fixes
> have landed.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
> 

Applied to fixes, thanks!

	Arnd
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