Bug 8666

Summary: glxgears causes graphics lockup on mga G400
Product: xorg Reporter: Jan Kundrát <jkt>
Component: Driver/mgaAssignee: Ian Romanick <idr>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: high CC: ajax
Version: 7.1 (2006.05)   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:

Description Jan Kundrát 2006-10-16 11:13:17 UTC
After upgrading from Xorg 7.0 to 7.1 (thus from Gentoo 
x11-drivers/xf86-video-mga-1.2.1.3 to x11-drivers/xf86-video-mga-1.4.1-r1 and 
later also x11-drivers/xf86-video-mga-1.4.2), running `glxinfo` reliably locks 
the screen (monitor, keyboard LEDs, Ctrl+Alt+Backspace, mouse movements) up. 
Rest of the system is usable (ssh access works). After killing X and calling 
`chvt 1`, the screen remains unusable (2.6.16-gentoo-r3 and 2.6.18-gentoo 
kernels, no framebuffer), the only solution is reboot. /var/log/Xorg.0.log 
contains a lot of lines like this one:

(EE) MGA(0): [dri] Idle timed out, resetting engine... 

I've tried some workarounds (Option "ForcePciDma" "yes", 
Option "OldDmaInit" "yes" and also both of them), yet the result is the same. 
As a temporary solution, I've downgraded my mga driver to 1.2.1.3. Now even 
`glxinfo` stops, but it can be killed by Ctrl+C and no X lockup occurs.

My mesa version is media-libs/mesa-6.5.1-r1, upgraded from 
media-libs/mesa-6.4.2-r2.

Please note that I haven't had any troubles for last year or so when running 
older Xorg versions, *including* 7.0.

Let me know if I can help in any way.
Comment 1 Alex Deucher 2006-10-16 19:29:54 UTC
you need a newer mga driver (1.4.2 or 1.4.3) or the mga driver from git head. 
The locking was broken on mga with AIGLX on 7.1.
Comment 2 Jan Kundrát 2006-10-17 01:44:31 UTC
As I've already stated in the original report, it hangs up with 1.4.2 as well. 
Now I've tried 1.4.3 and the behavior is the same.

Using 1.2.1.3 causes DRI not to work, but at least it doesn't crash when some 
application tries to use it.

Reopening.
Comment 3 Ian Romanick 2006-10-25 15:24:06 UTC
I had thought that I was seeing bug #473.  However, after some more
experimentation, I believe that I'm actually seeing this bug.

Jan, what sort of system are you on?  I'm seeing this on an AGP G400 in an
Athlon64 box.
Comment 4 Jan Kundrát 2006-10-26 05:59:30 UTC
(In reply to comment #3)
> Jan, what sort of system are you on?

x86 Athlon Thunderbird, Matrox G400 (AGP model with 32 MB of video RAM), 
motherboard is an ECS K7VZA, iirc. If you're interested in kernel and/or Xorg 
configs, let me know.
Comment 5 Ian Romanick 2006-10-26 18:21:48 UTC
I've bisected this down to commit 07373669514b104a11fb1b4ed5214f3764c83a2f as
the first bad change.  This was when ajax added support for the G200SE.  I
reviewed this change when he committed it, and I don't believe that it should
have had any impact on G400 class chips.

I'll continue to investigate.
Comment 6 Ian Romanick 2006-10-26 19:42:26 UTC
(In reply to comment #5)
> I've bisected this down to commit 07373669514b104a11fb1b4ed5214f3764c83a2f as
> the first bad change.  This was when ajax added support for the G200SE.  I
> reviewed this change when he committed it, and I don't believe that it should
> have had any impact on G400 class chips.
> 
> I'll continue to investigate.

I've tracked the problem down to the following change.  I have no idea why this
would have any impact what so ever.  If I take
07373669514b104a11fb1b4ed5214f3764c83a2f and revert this change, and this change
*only*, it starts working properly.

I've stared at it quite a bit, and it feels like one of those PC-lint mind
benders.  Ugh. :(

--- a/src/mga_dacG.c
+++ b/src/mga_dacG.c
@@ -688,6 +760,10 @@ MGA_NOT_HAL(
 		   ((i == 0x2c) || (i == 0x2d) || (i == 0x2e) ||
 		    (i == 0x4c) || (i == 0x4d) || (i == 0x4e))))
 		 continue; 
+	      if (((pMga->Chipset ==  PCI_CHIP_MGAG200_SE_A_PCI) ||
+		   (pMga->Chipset ==  PCI_CHIP_MGAG200_SE_B_PCI)) &&
+		   (i == 0x2C) || (i == 0x2D) || (i == 0x2E))
+	         continue;
 	      outMGAdac(i, mgaReg->DacRegs[i]);
 	   }
 	   
Comment 7 Ian Romanick 2006-10-26 19:57:17 UTC
Fixed.  && takes precedence over ||.  I'll push a new release, 1.4.3.1, tomorrow.
Comment 8 Jan Kundrát 2006-10-29 15:20:35 UTC
Yup, 1.4.4 fixes my problem. Thanks a lot for your effort, it's really 
appreciated.

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