linux-kernel - Re: 4.1 touchscreen regression on n900 -- pinpointed [was Re: linux-n900 v4.1-rc4]

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Message-ID: <20150529192505.GA28987@amd>
Date:	Fri, 29 May 2015 21:25:05 +0200
From:	Pavel Machek <pavel@....cz>
To:	Sebastian Reichel <sre@...nel.org>,
	kernel list <linux-kernel@...r.kernel.org>,
	maxime.ripard@...e-electrons.com, dmitry.torokhov@...il.com
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
Subject: Re: 4.1 touchscreen regression on n900 -- pinpointed [was Re:
 linux-n900 v4.1-rc4]

On Fri 2015-05-29 21:08:16, Pavel Machek wrote:
> Hi!
> 
> > mh I remember having problems with tsc2005 before. It helped to
> > reset the controller (should actually happen automatically when it
> > hangs, but I'm not sure, that it actually works).
> 
> Ok, I did some more testing, and found out rather bogus values in
> evtest:
> 
> Input device name: "TSC2005 touchscreen"
> Supported events:
>   Event type 0 (EV_SYN)
>   Event type 1 (EV_KEY)
>   Event code 330 (BTN_TOUCH)
>   Event type 3 (EV_ABS)
>   Event code 0 (ABS_X)
>   Value   2514
>  Min        0
>  Max        0
>  Fuzz       4
> 
> Which made me go through the git logs, and these patches looked
> suspicious. After a revert... yes, touchscreen works as well as it
> worked before.
> 
> 0a363a380954e10fece7cd9931b66056eeb07d56
> 3eea8b5d68c801fec788b411582b803463834752
> 
> (It is impossible to revert just 3eea..)

Hmm, I see:

                touchscreen-max-x = <4096>;
                touchscreen-max-y = <4096>;
...that's n900 dts.. this should be size-x/size-y... so we have a bug
in dts.

But the 3eea8b5d68c801fec788b411582b803463834752 is buggy, it should
not overwrite ->maximum for axis it has no devicetree data for.

Maybe replacing

+       if (maximum || fuzz)

in 3eea to (maximum && fuzz)... would help, but it is late in the
cycle now, so I'd suggest just reverting 3eea8b.

Thanks,
									Pavel 
				
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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