[Bug 54575] [GM45] boot-up broken in kernel 3.4.10 - screen stays blank (bad patch identified)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54575

--- Comment #26 from Egbert Eich <eich at pdx.freedesktop.org> ---
This issue is fixed in the current upstream kernel, however it is definitely an
issue in the 3.0.x longterm kernel:
On some Q43/Q45 chipsets (device ID 0x2e12) this issue doesn't only happen
occasionally but permanently.
It turns out that the two upstream commits:

   commit f01db988ef6f6c70a6cc36ee71e4a98a68901229
   Author: Sean Paul <seanpaul at chromium.org>
   Date:   Fri Mar 16 12:43:22 2012 -0400

       drm/i915: Add wait_for in init_ring_common

    I have seen a number of "blt ring initialization failed" messages
    where the ctl or start registers are not the correct value. Upon further
    inspection, if the code just waited a little bit, it would read the
    correct value. Adding the wait_for to these reads should eliminate the
    issue.

and

   commit 3eef8918ff440837f6af791942d8dd07e1a268ee
   Author: Chris Wilson <chris at chris-wilson.co.uk>
   Date:   Mon Jun 4 17:05:40 2012 +0100

       drm/i915: Mark the ringbuffers as being in the GTT domain

    By correctly describing the rinbuffers as being in the GTT domain, it
    appears that we are more careful with the management of the CPU cache
    upon resume and so prevent some coherency issue when submitting commands
    to the GPU later. A secondary effect is that the debug logs are then
    consistent with the actual usage (i.e. they no longer describe the
    ringbuffers as being in the CPU write domain when we are accessing them
    through an wc iomapping.)


are needed to fix this issue.

Both commits are part of 3.2.x and 3.4.x stable however not of 3.0.x.

Commit b7884eb45ec98c0d34c7f49005ae9d4b4b4e38f6 may also be useful to have,
however in the context of the hardware that I have tested it is not required.

Will notify stable@

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