linux-kernel - Re: [PATCH 1/2] SOUND: kill gameport bits

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Message-ID: <20140820144746.GA18099@core.coreip.homeip.net>
Date:	Wed, 20 Aug 2014 07:48:05 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Andreas Mohr <andi@...as.de>
Cc:	Takashi Iwai <tiwai@...e.de>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Vojtech Pavlik <vojtech@...e.cz>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH 1/2] SOUND: kill gameport bits

On Wed, Aug 20, 2014 at 04:27:19PM +0200, Andreas Mohr wrote:
> > > > Also, I'm left wondering why e.g. my Athlon XP system (a very popular
> > > > choice for longer times) would be affected by Cpufreq...
> > > > And there are no details on how exactly cpufreq is a problem or how this
> > > > timing issue could be fixed...
> > > 
> > > If you take a look at gameport_measure_speed() in gameport.c you will see that
> > > it counts cycles for timing, which obviously does not work that well when CPU
> > > frequency changes.
> > > 
> > > The bugs have been opened in bugzilla/reported on lists ages ago but nobody
> > > stepped up to fix that.
> 
> He probably meant one issue filed about this problem here:
> "Direct use of tsc: Analog joystick doesn't work properly with CPU
> frequency scaling activated"
> https://bugzilla.kernel.org/show_bug.cgi?id=12297
> right?

Right. There is also about a3d joystick not workign and I think a few others.

> 
> > Hm, can't we just use the standard ktime for measuring the time diff?
> > And, I guess only few programs care the speed parameter.
> 
> For clocksource matters, I've got an initial patch for Azt3328 which
> adds its 1MHz timer as a clocksource, which probably means that on this
> hardware the gameport would be accurate for both digital and non-digital
> modes (not that that would help much for machines without this soundcard
> which also don't sport a high-res timer...).
> 
> Since I've got some more patches waiting for some gameport compatible
> soundcard devices, I should be able to take this opportunity to retest
> gameport support, too...
> And since there's in fact my VIA system which has my second azt3328 in
> its single-slot PCI and which in fact probably is a cpufreq system,
> I might be able to work on fixing the cpufreq timer issue (but if
> Vojtech managed to golden his offer to work on a fix to this issue, I
> would be far from unhappy :).
> 
> 
> 
> BTW, I think I spotted a bug in the gameport removal commit (one driver
> did an if (!joystick) ... where the subsequent line was removed as well
> even though logically it quite likely shouldn't).
> 
> 
> From my POV it would be much more favourable to do this relatively simple(??)
> timer fix rather than removing an entire subsystem since it's partially(?)
> broken.

Fair enough. If you send me patches that fixes issues then I do not see any
problem with it staying in. Vojtech also promised to dig out his old hardware.

Thanks.

-- 
Dmitry
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