[Bug 82431] New: Garbled screen on boot

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=82431

            Bug ID: 82431
           Summary: Garbled screen on boot
           Product: Drivers
           Version: 2.5
    Kernel Version: All after 3.13.6-20
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: fedevx@yahoo.com
        Regression: No

When using any kernel higher than 3.13.6-20 (all the way to 3.16), my Toshiba
M840's screen gets garbled after Grub (grub itself is fine).

In particular, because my whole drive is encrypted, I see the garbled screen
when the prompt for the encryption key comes up.

I have the issue with my OpenSUSE installation and when booting off Archlinux's
installer.

I'm not sure if this is relevant but this happens on UEFI, if I change the
setting back to BIOS compatibility, at least on the Archlinux's installer, the
issue goes away. I can't test this on OpenSUSE since it is already set to UEFI
and will not boot on BIOS compatibility mode.

The issue has quite an impact since I can't bootup in a usable way, any Linux
distribution with a kernel newer than the one stated above.

I did a kernel bisect and found the below commit to be the cause of the issue:

[919cf555c04e16dafb1fba56904eb23889a812c3] drm/radeon: disable dpm on BTC
919cf555c04e16dafb1fba56904eb23889a812c3 is the first bad commit
commit 919cf555c04e16dafb1fba56904eb23889a812c3
Author: Alex Deucher <alexander.deucher@amd.com>
Date:   Sat Jan 11 10:55:55 2014 -0500

    drm/radeon: disable dpm on BTC

    Still unstable on some boards.

    Bugs:
    https://bugs.freedesktop.org/show_bug.cgi?id=73053
    https://bugzilla.kernel.org/show_bug.cgi?id=68571

    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Cc: 3.13 <stable@vger.kernel.org> # 3.13

:040000 040000 c03cf693d8be0e49e0b431b968c4934324344d57
f4fa27f78f5ff03216036f8bcdc3978b274b812f M      drivers

Thanks!


Details about my GFX card:

21: PCI 100.0: 0300 VGA compatible controller (VGA)             
  [Created at pci.319]
  Unique ID: VCu0.dkF2+KIVH8C
  Parent ID: vSkL.zuRwVyuZRN1
  SysFS ID: /devices/pci0000:00/0000:00:01.0/0000:01:00.0
  SysFS BusID: 0000:01:00.0
  Hardware Class: graphics card
  Model: "ATI VGA compatible controller"
  Vendor: pci 0x1002 "ATI Technologies Inc"
  Device: pci 0x6840 
  SubVendor: pci 0x1179 "Toshiba America Info Systems"
  SubDevice: pci 0xfb81 
  Driver: "radeon"
  Driver Modules: "drm"
  Memory Range: 0xb0000000-0xbfffffff (ro,non-prefetchable)
  Memory Range: 0xc0000000-0xc001ffff (rw,non-prefetchable)
  I/O Ports: 0x3000-0x3fff (rw)
  Memory Range: 0xc0040000-0xc005ffff (ro,non-prefetchable,disabled)
  IRQ: 43 (76519 events)
  Module Alias: "pci:v00001002d00006840sv00001179sd0000FB81bc03sc00i00"
  Driver Info #0:
    Driver Status: radeon is active
    Driver Activation Cmd: "modprobe radeon"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #9 (PCI bridge)
-----------

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