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<body><span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [965g] Undetected bit17 swizzling (note desktop not mobile)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=90725">bug 90725</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>FIXED
</td>
</tr></table>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [965g] Undetected bit17 swizzling (note desktop not mobile)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=90725#c51">Comment # 51</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [965g] Undetected bit17 swizzling (note desktop not mobile)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=90725">bug 90725</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>Should be all fixed up now:
commit a53f2afb7e3dfc2c7acbb0c015b44783d99d8119
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
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 <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
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 <<a href="mailto:ccr@tnsp.org">ccr@tnsp.org</a>>
Tested-by: Matti Hämäläinen <<a href="mailto:ccr@tnsp.org">ccr@tnsp.org</a>>
References: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [965g] Undetected bit17 swizzling (note desktop not mobile)"
href="show_bug.cgi?id=90725">https://bugs.freedesktop.org/show_bug.cgi?id=90725</a>
Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Cc: Matti Hämäläinen <<a href="mailto:ccr@tnsp.org">ccr@tnsp.org</a>>
Cc: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>>
Cc: Jani Nikula <<a href="mailto:jani.nikula@intel.com">jani.nikula@intel.com</a>>
Cc: <a href="mailto:stable@vger.kernel.org">stable@vger.kernel.org</a>
Reviewed-by: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>>
Link:
<a href="http://patchwork.freedesktop.org/patch/msgid/1447927085-31726-1-git-send-email-chris@chris-wilson.co.uk">http://patchwork.freedesktop.org/patch/msgid/1447927085-31726-1-git-send-email-chris@chris-wilson.co.uk</a>
Signed-off-by: Jani Nikula <<a href="mailto:jani.nikula@intel.com">jani.nikula@intel.com</a>></pre>
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