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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [HSW] *ERROR* crtc 21: Can't calculate constants, dotclock = 0!"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91428">91428</a>
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<th>Summary</th>
<td>[HSW] *ERROR* crtc 21: Can't calculate constants, dotclock = 0!
</td>
</tr>
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<th>Product</th>
<td>DRI
</td>
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<th>Version</th>
<td>XOrg git
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
</td>
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<th>OS</th>
<td>Linux (All)
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>DRM/Intel
</td>
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<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
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<th>Reporter</th>
<td>andreas.reis@gmail.com
</td>
</tr>
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>CC</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr></table>
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<pre>Getting said error both on my HSW 4200U and 4770. No apparent consequences or
related dmesg lines. Driver module is compiled-in.
[drm:drm_calc_timestamping_constants] *ERROR* crtc 21: Can't calculate
constants, dotclock = 0!
Kernel is drm-nightly-intel started with i915_enable_rc6=7. On 4770:
[ 0.796626] [drm] Initialized drm 1.1.0 20060810
[ 0.796908] [drm] Memory usable by graphics device = 2048M
[ 0.796909] [drm] VT-d active for gfx access
[ 0.796910] checking generic (d0000000 300000) vs hw (d0000000 10000000)
[ 0.796910] fb: switching to inteldrmfb from EFI VGA
[ 0.796918] Console: switching to colour dummy device 80x25
[ 0.796955] [drm] Replacing VGA console driver
[ 0.801751] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 0.801752] [drm] Driver supports precise vblank timestamp query.
[ 0.801761] [drm] DMAR active, disabling use of stolen memory
[ 0.801803] vgaarb: device changed decodes:
PCI:0000:00:02.0,olddecodes=io+mem,decodes=none:owns=io+mem
[ 0.868011] [drm:drm_calc_timestamping_constants] *ERROR* crtc 21: Can't
calculate constants, dotclock = 0!
[ 0.873265] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no)
[ 0.873534] acpi device:60: registered as cooling_device13
[ 0.873571] input: Video Bus as
/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input2
[ 0.873582] [drm] Initialized i915 1.6.0 20150717 for 0000:00:02.0 on minor
0</pre>
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