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<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [HSW] kms_flip atomic warnings"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91579#c13">Comment # 13</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [HSW] kms_flip atomic warnings"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91579">bug 91579</a>
from <span class="vcard"><a class="email" href="mailto:jbarnes@virtuousgeek.org" title="Jesse Barnes <jbarnes@virtuousgeek.org>"> <span class="fn">Jesse Barnes</span></a>
</span></b>
<pre>Update from yesterday's experiments. I confirmed that the frame counter is
incrementing correctly and at the right rate, but the scanline register read
returns 0 when read around the start of vblank. A sequence of reads might
return:
0
0
0
<delay 1us>
1600
This happens right around the time the frame counter increments, so when this
happens we trigger the warning in the atomic update end function. I posted a
patch to workaround this by ignoring scanline read results for the first couple
of lines in the display; that should be safe everywhere and lets us schedule
things correctly when we hit this case.</pre>
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