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<base href="https://bugs.freedesktop.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - 4k monitor at 48hz leads to blank screen"
href="https://bugs.freedesktop.org/show_bug.cgi?id=86462">86462</a>
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<th>Summary</th>
<td>4k monitor at 48hz leads to blank screen
</td>
</tr>
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<th>Product</th>
<td>DRI
</td>
</tr>
<tr>
<th>Version</th>
<td>XOrg git
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<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>delamonpansie@gmail.com
</td>
</tr>
<tr>
<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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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=109723" name="attach_109723" title="boot dmesg">attachment 109723</a> <a href="attachment.cgi?id=109723&action=edit" title="boot dmesg">[details]</a></span>
boot dmesg
Error description : attemp to drive monitor at 48hz leads to blank screen.
Expected behhavior: working setup, since DP MST should able to drive this.
Hardware: dell e7440 with e-port+ port replicator, IBM T221 monitor. E-port+
replicator Synaptics VMM2320 MST HUB running updated firmware A01.
Monitor connected via two DualDVI ports, each running 1920x2400 resolution.
EDID is overriden with drm_kms_helper.edid_firmware.
kernel version: 3cb89f9 drm-intel-nightly: 2014y-11m-18d-15h-23m-21s UTC
integration manifest
EDID override is not strictly neccecary, because modes are added via xrandr:
xrandr --newmode "1920x2400_32.00" 202.75 1920 2056 2256 2592 2400 2403 2413
2447 -hsync +vsync
xrandr --addmode DP2 1920x2400_32.00
xrandr --addmode DP3 1920x2400_32.00
xrandr --output eDP1 --mode 1920x1080
xrandr --output DP2 --right-of eDP1 --mode 1920x2400_32.00
xrandr --output DP3 --right-of DP2 --mode 1920x2400_32.00
This monitor succesfully works on desktop system with nvidia card with refresh
up to 55Hz, however setting refresh higher than 32Hz when runnig on dell
results in a blank screen. 32hz mode is added and selected via xrandr.
I have noticed that setting 48hz mode leads to follwing error in dmesg:
[drm:drm_dp_check_act_status] failed to get ACT bit 1 after 30 retries
So, made following changes and retried
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 5682d7e..9afd0a9 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2405,13 +2405,14 @@ int drm_dp_check_act_status(struct
drm_dp_mst_topology_mgr *mgr)
count++;
udelay(100);
- } while (count < 30);
+ } while (count < 300);
if (!(status & DP_PAYLOAD_ACT_HANDLED)) {
DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n",
status, count);
ret = -EINVAL;
goto fail;
- }
+ } else
+ DRM_DEBUG_KMS("get ACT bit %d after %d retries\n", status,
count);
return 0;
fail:
return ret;
Still blank screen at 48hz, the dmesg difference is:
-[drm:drm_dp_check_act_status] get ACT bit 3 after 18 retries
+[drm:drm_dp_check_act_status] get ACT bit 3 after 27 retries
Attaching dmesg from nvidia, from 32Hz running ok, from 48Hz with blank screen,
xrandr --verbose</pre>
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