[Bug 90725] [965g] Undetected bit17 swizzling (note desktop not mobile)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90725

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #51 from Chris Wilson <chris at chris-wilson.co.uk> ---
Should be all fixed up now:

commit a53f2afb7e3dfc2c7acbb0c015b44783d99d8119
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Nov 19 09:58:05 2015 +0000

    drm/i915: Mark uneven memory banks on gen4 desktop as unknown swizzling

    We have varied reports of swizzling corruption on gen4 desktop, and
    confirmation that one at least is triggered by uneven memory banks
    (L-shaped memory). The implication is that the swizzling varies between
    the paired channels and the remainder of memory on the single channel. As
    the object then has unpredictable swizzling (it will vary depending on
    exact page allocation and may even change during the object's lifetime as
    the pages are replaced), we have to report to userspace that the swizzling
    is unknown.

    However, some existing userspace is buggy when it meets an unknown
    swizzling configuration and so we need to tell another white lie and
    mark the swizzling as NONE but report it as UNKNOWN through the extended
    get-tiling-ioctl. See

    commit 5eb3e5a5e11d14f9deb2a4b83555443b69ab9940
    Author: Chris Wilson <chris at chris-wilson.co.uk>
    Date:   Sun Jun 28 09:19:26 2015 +0100

        drm/i915: Declare the swizzling unknown for L-shaped configurations

    for the previous example where we found that telling the truth to
    userspace just ends up in a world of hurt.

    Also since we don't truly know what the swizzling is on the pages, we
    need to keep them pinned to prevent swapping as the reports also
    suggest that some gen4 devices have previously undetected bit17
    swizzling.

    v2: Combine unknown + quirk patches to prevent userspace ever seeing
    unknown swizzling through the normal get-tiling-ioctl. Also use the same
    path for the existing uneven bank detection for mobile gen4.

    Reported-by: Matti Hämäläinen <ccr at tnsp.org>
    Tested-by: Matti Hämäläinen <ccr at tnsp.org>
    References: https://bugs.freedesktop.org/show_bug.cgi?id=90725
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Matti Hämäläinen <ccr at tnsp.org>
    Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
    Cc: Jani Nikula <jani.nikula at intel.com>
    Cc: stable at vger.kernel.org
    Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
    Link:
http://patchwork.freedesktop.org/patch/msgid/1447927085-31726-1-git-send-email-chris@chris-wilson.co.uk
    Signed-off-by: Jani Nikula <jani.nikula at intel.com>

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