On Thu, 21 Apr 2011, Mike Isely wrote:
> On Thu, 21 Apr 2011, Chris Wilson wrote:
>
> > On Thu, 21 Apr 2011 17:30:21 -0500 (CDT), Mike Isely <is...@isely.net>
> > wrote:
> > > It looks like the driver did notice the specified mode and used it -
> > > because the display's refresh rate did get adjusted and the overall
> > > resolution is correct. However the display timings are slightly "off",
> > > the image is stretched a few pixels off the right edge and a few lines
> > > off the bottom edge. Yet the same modeline given to "video=" in
> > > combination with my controversial disable-fixed-mode patch however
> > > produces a perfectly aligned image.
> >
> > Adding a few printk will help. And perhaps comparing the resultant register
> > settings with intel_reg_dumper.
>
> Oh absolutely. But right now I'm not doing a very fair apples-to-apples
> comparison. I need to address that first and make sure nothing else is
> influencing this.
>
> -Mike
>
Chris:
Sorry this simple thing has taken 2 weeks, but I'm having to time-slice
a lot of different tasks at the moment. People keep pulling me away
from this :-( However I've finally dug down and found the problem.
There's a bug in the function drm_mode_parse_command_line_for_connector
(the subject of this thread) that is leaving the margins field
uninitialized. This has been the cause all along for the differing
results I was getting.
This bug didn't start with the underlying patch ("Use
i915.lvds_fixed_mode= as a last resort"). I also looked at
drm_fb_helper_connector_parse_command_line from before this patch and it
looks like the same bug exists there. Amazing that nobody has noticed
this.
Patch to follow.
-Mike
--
Mike Isely
isely @ isely (dot) net
PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8
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