Date:	Thu, 4 Dec 2008 01:07:36 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	"Dave Airlie" <airlied@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Benny Amorsen <benny+usenet@...rsen.dk>
Subject: Re: vanilla kernels hang randomly under Fedora 10 on system with Radeon card

On Wednesday 03 December 2008, Bartlomiej Zolnierkiewicz wrote:
> On Tuesday 02 December 2008, Dave Airlie wrote:
> > On Tue, Dec 2, 2008 at 8:42 AM, Bartlomiej Zolnierkiewicz
> > <bzolnier@...il.com> wrote:
> > >
> > > Hi,
> > >
> > > After Fedora 9 -> Fedora 10 upgrade vanilla kernels which previously
> > > worked fine (next-20081128 and next-20081121) started to hang randomly
> > > on my Pentium M / 855PM / RV350 laptop.  Since (surprisingly) stock
> > > Fedora kernel (2.6.27.5-117.fc10.i686) was not affected I got the idea
> > > that either userspace changes uncovered some kernel regression or some
> > > Fedora specific patch must be fixing the issue.  Unfortunately vanilla
> > > 2.6.27 also freezed so after the usual pain caused by hitting bunch of
> > > unrelated problems [1] it turned out that drm-modesetting-radeon.patch
> > > is the magic patch and CONFIG_DRM_RADEON_KMS is the magic change.  With
> > > the patch and enabling the option next-20081128 works stable again...
> > >
> > > Since the following error gets logged by kernel:
> > >
> > > [drm:drm_buffer_object_validate] *ERROR* Failed moving buffer. cef578c0 1444 4000027 10000a0
> > > [drm:drm_buffer_object_validate] *ERROR* Out of aperture space or DRM memory quota.
> > >
> > > and it also seems that system is more responsive now (it was kind of
> > > sluggish previously) my draft theory is that F9 -> F10 triggered some
> > > AGP memory management bug and CONFIG_DRM_RADEON_KMS happens to fix it
> > > but I'll leave figuring this up to the more knowledgeable people... ;)
> > 
> > Well KMS is a purely Fedora thing, and enabling it completely avoids
> > the old driver codepaths so
> > while it might fix it, its more by accident than design.
> > 
> > I'm trying to track down the rv3xx hangs with hpa at the moment as he
> > sees them also, something in
> >  the 2.6.26->2.6.27 timeframe. I'm hoping running the 2.6.26 drm on
> > the 2.6.27 will help narrow it down.
> > 
> > Bisecting 2.6.26->2.6.27 might also help.
> 
> It could be a different issue.  I tried 2.6.26, 2.6.25 and 2.6.24
> and they all hang (they all worked fine with Fedora 9)...
> 
> I will try some older kernels but I start thinking that the xorg's ati
> driver update is the main cause (xorg-x11-drv-ati-6.8.0-19.fc9.i386.rpm
> -> xorg-x11-drv-ati-6.9.0-54.fc10.i386.rpm).

I just went straight to trying downgrading the driver and the older driver
indeed works fine.  Then I tried to narrow down the problem and the lucky
winner this time is the cute (== undocumented and unsigned-off) patch
called radeon-6.9.0-remove-limit-heuristics.patch.  The newer driver with
only this patch reverted fixes hangs for vanilla kernels and drm errors
for Fedora kernel.  Also performance problems that I've noticed in the
meantime (slower playback of 720p videos, sluggish window scrolling in
kmail) are completely gone.  That being said I'm not entirely sure whether
the patch introduced the bug or it was only the trigger for it...

FWIW I've noticed that the patch seems to change the allocation+layout of
memory used by the driver:

@@ -524,13 +521,13 @@
 (II) RADEON(0): Depth moves disabled by default
 (==) RADEON(0): Not using accelerated EXA DownloadFromScreen hook
 (II) RADEON(0): Allocating from a screen of 65536 kb
-(II) RADEON(0): Will use 32 kb for hardware cursor 0 at offset 0x00bb8000
-(II) RADEON(0): Will use 32 kb for hardware cursor 1 at offset 0x00bbc000
-(II) RADEON(0): Will use 12000 kb for front buffer at offset 0x00000000
-(II) RADEON(0): Will use 12000 kb for back buffer at offset 0x00bc0000
-(II) RADEON(0): Will use 12000 kb for depth buffer at offset 0x01778000
-(II) RADEON(0): Will use 14720 kb for textures at offset 0x02330000
-(II) RADEON(0): Will use 14784 kb for X Server offscreen at offset 0x03190000
+(II) RADEON(0): Will use 32 kb for hardware cursor 0 at offset 0x011e0000
+(II) RADEON(0): Will use 32 kb for hardware cursor 1 at offset 0x011e4000
+(II) RADEON(0): Will use 18304 kb for front buffer at offset 0x00000000
+(II) RADEON(0): Will use 18304 kb for back buffer at offset 0x011e8000
+(II) RADEON(0): Will use 18304 kb for depth buffer at offset 0x023c8000
+(II) RADEON(0): Will use 5248 kb for textures at offset 0x035a8000
+(II) RADEON(0): Will use 5344 kb for X Server offscreen at offset 0x03ac8000
 drmOpenDevice: node name is /dev/dri/card0
 drmOpenDevice: open result is 11, (OK)
 drmOpenDevice: node name is /dev/dri/card0

full Xorg logs at kernel.org/pub/linux/kernel/people/bart/f9_to_f10_grind/

Thanks,
Bart

PS Since I was busy with debugging the problem I haven't noticed that you
have released the new driver package (xorg-x11-drv-ati-6.9.0-59.fc10),
however since it still contains the patch in question I don't think that
it would help (anyway I'll test it tomorrow, I'm too tired now)...
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