[Bug 94825] LVDS blank screen on GM45
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Mon Apr 11 04:12:26 UTC 2016
https://bugs.freedesktop.org/show_bug.cgi?id=94825
--- Comment #22 from Rob Kramer <rob at solution-space.com> ---
(In reply to Ville Syrjala from comment #21)
> I found something interesting in the opregion spec. Based on that I posted a
> few patches that could help here:
> https://lists.freedesktop.org/archives/intel-gfx/2016-April/091988.html
>
> Please test and report back.
OK, reverted your previous _DDC patch, applied these three. The result is a
blank screen. I added some debug statements in your opregion.c patch:
ret = swsci(dev, SWSCI_GBDA_PANEL_DETAILS, 0x0, &panel_details);
if (ret)
{
DRM_DEBUG_KMS ("Rob: return %d\n", ret);
return ret;
}
DRM_DEBUG_KMS ("Rob: panel details 0x%x\n", panel_details);
And in the log:
[drm:intel_opregion_get_panel_type] Rob: panel details 0x21000
Which would mean panel 0x10 according to the spec in your mail, which would be
good if you'd started counting at 1 :)
Next, I tried setting the mode to 1366x768 at 73.8M in the bios, and the output
changes to:
[drm:intel_opregion_get_panel_type] Rob: panel details 0x20d00
That is off by one too, but is still good news since it follows the BIOS
setting.. Trying the obvious fix works:
return ((panel_details >> 8) & 0xff) - 1;
> "Bits [15:8] - Panel Type
> Bits contain the panel type user setting from CMOS
> 00h = Not Valid, use default Panel Type & Timings from VBT
> 01h - 0Fh = Panel Number"
That would mean only 15 possible valid modes, right? But my BIOS has 16 in its
list already, and the correct mode happens to be the last one.
[No log attached, because nothing further of interest]
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