[Bug 74657] New: Mode detection fails on Dell Venue 8 Pro (due to bad EDID?)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=74657

          Priority: medium
            Bug ID: 74657
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: Mode detection fails on Dell Venue 8 Pro (due to bad
                    EDID?)
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: awilliam at redhat.com
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: DRM/Intel
           Product: DRI

Following on from https://bugs.freedesktop.org/show_bug.cgi?id=71977 . With
kernel 3.14-rc1 plus patches to fix various boot failures plus the reversion of
"drm/i915/vlv: re-enable hotplug detect based probing on VLV/BYT" (that's
71977), multiple testers have confirmed you can get KMS to work on Bay Trail
tablets.

On the Venue 8 Pro, the modesetting does not correctly discover the device's
preferred mode, though, which is 800x1280 (the screen's 'native' orientation is
portrait). It decides on 1024x768.

I've captured the EDID of the screen - I'll attach it. The thing that leaps out
to me as being incorrect is that the minimum hsync and vsync are both set to 0,
which is I believe outside the spec (Wikipedia sez it should be in the range of
1–255 kHz).

If I run monitor-parse-edid on the unmodified EDID, it barfs:

[adamw at adam data]$ monitor-parse-edid AUO00C4.bin 
bad HorizSync

with a version hex edited to bump the min hsync and vsync to 10 (hex, so
16kHz), it works:

[adamw at adam data]$ monitor-parse-edid AUO00C4_mod.bin 
EISA ID: AUO00c4
EDID version: 1.3
EDID extension blocks: 0
Screen size: 10.8 cm x 17.2 cm (8.00 inches, aspect ratio 0.63)
Gamma: 3.55
Digital signal
Max video bandwidth: 80 MHz

    HorizSync 16-173
    VertRefresh 16-60

    # Monitor preferred modeline (60.0 Hz vsync, 78.0 kHz hsync, ratio 0.62,
188 dpi)
    ModeLine "800x1280" 76.75 800 824 828 984 1280 1288 1292 1300 -hsync -vsync

I know the kernel code isn't the same as monitor-parse-edid, but it still seems
indicative.

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