Message-Id: <20090516164420.3319334c.akpm@linux-foundation.org>
Date:	Sat, 16 May 2009 16:44:20 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michel Dänzer <michel@...nzer.net>
Cc:	Karsten Mehrhoff <kawime@....de>,
	Shaohua Li <shaohua.li@...el.com>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.sourceforge.net,
	stable@...nel.org, Dave Airlie <airlied@...ux.ie>
Subject: Re: PROBLEM: 2.6.29.2 - AGP doesn't work anymore on my nforce2

On Mon, 04 May 2009 18:40:52 +0200 Michel D__nzer <michel@...nzer.net> wrote:

> On Mon, 2009-05-04 at 18:23 +0200, Karsten Mehrhoff wrote:
> > On Mon, 04 May 2009 17:07:40 +0200, Michel D__nzer wrote:
> > > On Mon, 2009-05-04 at 08:31 +0200, Karsten Mehrhoff wrote:
> > >> On Mon, 04 May 2009 03:41:51 +0200, Shaohua Li wrote:
> > >>> On Fri, May 01, 2009 at 09:22:19PM +0800, kawime@....de wrote:
> > >>>>> On Thu, 2009-04-30 at 17:59 -0700, Andrew Morton wrote:
> > >>>>>> On Thu, 30 Apr 2009 10:51:47 +0200
> > >>>>>> Karsten Mehrhoff wrote:
> > >>>>>>
> > >>>>>>> [1.]
> > >>>>>>> PROBLEM: No more agp card functionality with the patch 2.6.29.2 of
> > >>>>>> 'a/drivers/char/agp/generic.c'
> > >>>>>>>
> > >>>>>>> [2.]
> > >>>>>>> I compiled the kernel 2.6.29.2 with my .config of 2.6.29.1 and run
> > >>>>>> into problems with the speed of my ATI RADEON 9600 (rv350)
> > >>>>>>>
> > >>>>>>
> > >>>>>
> > >>>>> Is your problem speed issue ? ie just a slowdown ? Or does AGP stop
> > >>>>> working with this patch ? Slowdown is expected from this patch but
> > >>>>> it should hurt too much.
> > >>>>>
> > >>>>
> > >>>>                        2.6.29.1  | 2.6.29.2
> > >>>>                         --------  |  --------
> > >>>> glxgears             ~ 2900 FPS  |  ~ 75 FPS
> > >>>> glxgears -fullscreen ~  500 FPS  |  ~ 11 FPS
> > >>> Does this patch alone give so huge slowdown? From my little knowledge,
> > >>> xserver
> > >>> does agp pages allocation only at startup.
> > >>
> > >> I only reverted this patch in the source file  
> > >> (/drivers/char/agp/generic.c) and got back my old speed on 2.6.29.2.
> > >
> > > Is the DRI enabled in both cases? Compare the Xorg.0.log file and the
> > > output of
> > >
> > > dmesg|grep -e agp -e drm
> > >
> > 
> > 
> > *********************************
> > 2.6.29.2 (original) 
> > *********************************
> > 
> > $ dmesg|grep -e agp -e drm
> > $ dmesg|grep agp
> > [    0.861997] Linux agpgart interface v0.103
> > [   10.893793] agpgart: Detected NVIDIA nForce2 chipset
> > [   10.939070] agpgart-nvidia 0000:00:00.0: AGP aperture is 64M @ 0xe0000000
> 
> No drm lines?
> 
> 
> > $ glxinfo | grep direct
> > direct rendering: Yes
> 
> This is not a sufficient test anymore since swrast_dri.so is direct
> rendering but not hardware accelerated. Something like
> 
> glxinfo|grep render
> 
> can be used to verify both direct rendering and hardware acceleration
> (the latter but not the former is also possible with AIGLX).
> 
> 
> > (EE) RADEON(0): [agp] AGP failed to initialize. Disabling the DRI.
> 
> [...]
> 
> > For me it seems that agp failed to initialize because of the patch.
> 
> Indeed.
> 

Guys, can we rev this up again please?

AFAICT we have two problems and at least one of them is in 2.6.29.x and
is presumably headed into 2.6.30 as well.

a) 59de2bebabc5027f93df999d59cc65df591c3e6e made Karsten's AGP stop
   working.  This is very mysterious.

b) Someone, apparently karsten who has a mysterious gap in this
   thread (did someone go off-list) is apparently seeing a massive
   glxgears slowdown.  I don't know if that slowdown was attributed to
   the same commit.  Or is that the same bug?


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