Hi
thanks for your help.
Am 04.10.24 um 12:01 schrieb Ville Syrjälä:
On Fri, Oct 04, 2024 at 11:17:02AM +0200, Thomas Zimmermann wrote:
Hi
Am 02.10.24 um 18:15 schrieb Luck, Tony:
Thanks for the bug report. Can you provide the output of 'sudo lspci
-vvv' for the graphics device?
Thomas,
Sure. Here's the output (run on the v6.11.0 kernel)
Thanks. It doesn't look much different from other systems. IRQ is also
assigned.
Attached is a patch that fixes a possible off-by-one error in the
register settings. This would affect the bug you're reporting. If
possible, please apply the patch to your 6.12-rc1, test and report the
result.
Didn't one of these weird variants have some bug where the
CRTC startadd was not working? Is this one of those?
Yeah, but it seems unrelated.
That to me sounds like maybe linecomp has internally been
tied to be always active somehow. Perhaps that would
also prevent it from generating the interrupt...
Linecomp is usually set to vtotal and that disables the irq. When set to
vblank_start/vdisplay_end, it acts like a vblank IRQ. But the other
matrox drivers I saw (fbdev, Xorg-video-matrox) set the value -1, while
mgag200 doesn't. So there really is an off-by-one error.
Anyways, sounds like someone should just double check whether
the status bit ever get asserted or not. If yes, then the
problem must be with interrupt delivery, otherwise the
problem is that the internal interrupt is never even
generated. In the latter case you could try using the
vsync interrupt instead.
I didn't want to go into full debugging while there's a low-hanging fix
to try first. I'll probably take that patch anyway even if it doesn't
fix the reported bug.
Wrt. vsync: isn't that way to late for vblank events? Does DRM give any
timing guarantees? (It doesn't AFAIK.) Or does it just mean that a
vblank has happened at some point in the past?
Best regards
Thomas
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
