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<body><span class="vcard"><a class="email" href="mailto:jani.nikula@intel.com" title="Jani Nikula <jani.nikula@intel.com>"> <span class="fn">Jani Nikula</span></a>
</span> changed
<a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [BAT][SKL] igt@kms_flip@basic-flip-vs-dpms produces a dmesg-fail"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101167">bug 101167</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>NEEDINFO
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<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [BAT][SKL] igt@kms_flip@basic-flip-vs-dpms produces a dmesg-fail"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101167#c7">Comment # 7</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [BAT][SKL] igt@kms_flip@basic-flip-vs-dpms produces a dmesg-fail"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101167">bug 101167</a>
from <span class="vcard"><a class="email" href="mailto:jani.nikula@intel.com" title="Jani Nikula <jani.nikula@intel.com>"> <span class="fn">Jani Nikula</span></a>
</span></b>
<pre>(In reply to Marta Löfstedt from <a href="show_bug.cgi?id=101167#c6">comment #6</a>)
<span class="quote">> If I revert:
>
> "commit 9301397a63b3bf1090dffe846c6f1c8efa032236
> Author: Manasi Navare <<a href="mailto:manasi.d.navare@intel.com">manasi.d.navare@intel.com</a>>
> Date: Thu Apr 6 16:44:19 2017 +0300
>
> drm/i915: Implement Link Rate fallback on Link training failure"
>
> I can't reproduce the test failing. However I still get the dmesg-warn (see
> bug <a class="bz_bug_link
bz_status_NEW "
title="NEW - [BAT][SKL] *ERROR* failed to enable link training"
href="show_bug.cgi?id=101144">https://bugs.freedesktop.org/show_bug.cgi?id=101144</a> )</span >
Before the change, we plunge on with channel equalization regardless of
failures during clock recovery phase. By magic, on some machines it'll still
all work despite the errors.
Per spec, the correct thing to do is to check and handle the failures
gracefully, and reducing the link, which Manasi's commit attempts to do.
(In reply to Marta Löfstedt from <a href="show_bug.cgi?id=101167#c5">comment #5</a>)
<span class="quote">> But I since the issue hasn't been 100% reproducible I believe we need to
> find a root cause and not just slowing things down.</span >
Agreed. In this case it seems to boil down to DP aux channel communication. On
a whim, please try:
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fc691b8b317c..fb568f75939f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2431,6 +2431,8 @@ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int
mode)
{
int ret, i;
+ return;
+
/* Should have a valid DPCD by this point */
if (intel_dp->dpcd[DP_DPCD_REV] < 0x11)
return;</pre>
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