<html>
<head>
<base href="https://bugs.freedesktop.org/" />
</head>
<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 - [SKL][v4.3 bisected]SKL OpenCL performance reduced hugely"
href="https://bugs.freedesktop.org/show_bug.cgi?id=92975">bug 92975</a>
<br>
<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
</td>
</tr></table>
<p>
<div>
<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [SKL][v4.3 bisected]SKL OpenCL performance reduced hugely"
href="https://bugs.freedesktop.org/show_bug.cgi?id=92975#c4">Comment # 4</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [SKL][v4.3 bisected]SKL OpenCL performance reduced hugely"
href="https://bugs.freedesktop.org/show_bug.cgi?id=92975">bug 92975</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 meng from <a href="show_bug.cgi?id=92975#c2">comment #2</a>)
<span class="quote">> No "i915.preliminary_hw_support=1" set in grub.</span >
Before v4.3 you don't get SKL gfx support without that, or
CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y.
When running pre-v4.3, do you see something along these lines in the dmesg:
"""
This hardware requires preliminary hardware support.
See CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT, and/or modparam
preliminary_hw_support
"""
<span class="quote">> By skipping many commits, found out the first bad commit:
> commit 3bbaba0ceaa254c9ee261e329bfd92e4ba4fe32a
> Author: Peter Antoine <<a href="mailto:peter.antoine@intel.com">peter.antoine@intel.com</a>>
> Date: Fri Jul 10 20:13:11 2015 +0300
>
> drm/i915: Added Programming of the MOCS</span >
Please pick a badly performing kernel (verify that it does!) and then try this
on top:
diff --git a/drivers/gpu/drm/i915/intel_lrc.c
b/drivers/gpu/drm/i915/intel_lrc.c
index 06180dce954e..0eaeccdc5a49 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1867,7 +1867,7 @@ static int gen8_init_rcs_context(struct
drm_i915_gem_request *req)
if (ret)
return ret;
- ret = intel_rcs_context_init_mocs(req);
+ ret = 1;
/*
* Failing to program the MOCS is non-fatal.The system will not
* run at peak performance. So generate an error and carry on.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the QA Contact for the bug.</li>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>