Bug 92297 - dithering detected incorrectly
Summary: dithering detected incorrectly
Status: NEW
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/nouveau (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: medium minor
Assignee: Nouveau Project
QA Contact: Xorg Project Team
Depends on:
Reported: 2015-10-05 19:46 UTC by Avi Kivity
Modified: 2015-10-05 21:50 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

vbios.rom (59.50 KB, application/octet-stream)
2015-10-05 19:46 UTC, Avi Kivity
no flags Details

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Description Avi Kivity 2015-10-05 19:46:56 UTC
Created attachment 118681 [details]

01:00.0 VGA compatible controller: NVIDIA Corporation GF108GLM [NVS 5200M] (rev a1)

This is a laptop; the laptop screen displays some colors as flickering vertically striped patterns, which IRC/imirkin diagnosed as unneeded dithering.  Disabling dithering with xrandr fixes the issue.
Comment 1 Ilia Mirkin 2015-10-05 20:13:56 UTC
Please grab a copy of envytools (github.com/envytools/envytools) and also provide the output of

nvapeek 101000
Comment 2 Avi Kivity 2015-10-05 20:15:49 UTC
00101000: 9f5cb098
Comment 3 Ilia Mirkin 2015-10-05 21:50:02 UTC
Well, unless I'm misreading the bios (entirely possible), the FP data pointed to by the offset in BIT table 'L' suggests that it's not a 8bpc screen.

bios->fp.strapless_is_24bit = bios->data[bios->fp.lvdsmanufacturerpointer + 4];

lvdsmanufacturerpointer = 56df

and 0x56e3 == 0. So nouveau is correctly turning on dithering based on the information available to it. However perhaps that information isn't trustworthy for fermi+. Or perhaps there's another bit somewhere.

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