Re: [PATCH v4 1/2] i8042: Add forcenorestore quirk to leave controller untouched even on s3

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Werner Sembach <wse@tuxedocomputers.com>
Cc: hdegoede@redhat.com, linux-input@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/2] i8042: Add forcenorestore quirk to leave controller untouched even on s3
Date: Tue, 9 Jan 2024 13:48:24 -0800	[thread overview]
Message-ID: <ZZ2_KMGdokHNWcNL@google.com> (raw)
In-Reply-To: <20240104183118.779778-2-wse@tuxedocomputers.com>

Hi Werner,

On Thu, Jan 04, 2024 at 07:31:17PM +0100, Werner Sembach wrote:
> On s3 resume the i8042 driver tries to restore the controller to a known
> state by reinitializing things, however this can confuse the controller
> with different effects. Mostly occasionally unresponsive keyboards after
> resume.
> 
> These issues do not rise on s0ix resume as here the controller is assumed
> to preserved its state from before suspend.
> 
> This patch adds a quirk for devices where the reinitialization on s3 resume
> is not needed and might be harmful as described above. It does this by
> using the s0ix resume code path at selected locations.
> 
> This new quirk goes beyond what the preexisting reset=never quirk does,
> which only skips some reinitialization steps.

I think the original change mentioned not only issues on resume, but
also after boot, which this one does not address, at least directly, so
I am not sure if this patch is the proper replacement.

I would also like to understand better what exact step is troublesome,
as I would be surprised if any interaction with the keyboard
controller while suspending causes the issue to manifest. Is it enough,
by chance, to skip restoring MUX mode and reset?

Also, shoudl this system use s2idle by chance?

Thanks.

-- 
Dmitry