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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - eDP panel exhibits sparse random noise and flickering (link issue), forcing DP DDI profile helps [Lenovo T450s]"
href="https://bugs.freedesktop.org/show_bug.cgi?id=94087">94087</a>
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<th>Summary</th>
<td>eDP panel exhibits sparse random noise and flickering (link issue), forcing DP DDI profile helps [Lenovo T450s]
</td>
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<th>Product</th>
<td>DRI
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
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<th>OS</th>
<td>Linux (All)
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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
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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>
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<th>Reporter</th>
<td>alex@alexanderweb.de
</td>
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<th>CC</th>
<td>ben@bwidawsk.net, intel-gfx-bugs@lists.freedesktop.org
</td>
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<th>i915 features</th>
<td>display/eDP
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<pre>Created <span class=""><a href="attachment.cgi?id=121659" name="attach_121659" title="DDI profile switch from eDP to DP by ben@bwidawsk.net">attachment 121659</a> <a href="attachment.cgi?id=121659&action=edit" title="DDI profile switch from eDP to DP by ben@bwidawsk.net">[details]</a></span> <a href='page.cgi?id=splinter.html&bug=94087&attachment=121659'>[review]</a>
DDI profile switch from eDP to DP by <a href="mailto:ben@bwidawsk.net">ben@bwidawsk.net</a>
The internal eDP panel of my recently bought Lenovo Thinkpad T450s exhibits
sparse random noise and flickering (link issue). The CPU is i5200U (Broadwell).
Video of the symptom: <a href="http://ghostbusters.alexanderweb.de/t450s.mov">http://ghostbusters.alexanderweb.de/t450s.mov</a>
Ben and I discovered that forcing the DP DDI profile works around the problem.
See the patch by Ben (<a href="mailto:ben@bwidawsk.net">ben@bwidawsk.net</a>) that I attached.
Ben suspects the vswing to be incorrectly inferred from VBT.
Found on Kernel 4.2.0-27-generic, also affected: 4.4.1-vanilla.
Suggested fixes by Ben:
- Check whether VBT is correctly read and/or whether it is faulty.
- Either:
- Provide a vswing override that works on BDW (edp_vswing does not)
- Optionally contact Lenovo to fix the T450(s) BIOS (current one used:
JBET55WW, 1.20) to have a correct VBT.
- Or: Fix VBT parsing.
Kernel params used:
- Setting "i915.enable_ips=0 i915.modeset=1 i915.lvds_use_ssc=0" does not
change the behaviour.
Kernel messages related to VBT:
[drm:validate_vbt] Using VBT from OpRegion: $VBT HASWELL d
[drm:parse_general_features] BDB_GENERAL_FEATURES int_tv_support 0
int_crt_support 0 lvds_use_ssc 1 lvds_ssc_freq 120000 display_clock_mode 0
fdi_rx_polarity_inverted 0
[drm:parse_general_definitions] crt_ddc_bus_pin: 0
[drm:parse_lfp_panel_data] DRRS supported mode is static
[drm:parse_lfp_panel_data] Found panel mode in BIOS VBT tables:
[drm:drm_mode_debug_printmodeline] Modeline 0:"1920x1080" 0 141000 1920 1936
1952 2104 1080 1083 1097 1116 0x8 0xa
[drm:parse_lfp_panel_data] VBT initial LVDS value 30033c
[drm:parse_lfp_backlight] VBT backlight PWM modulation frequency 220 Hz, active
high, min brightness 3, level 255
[drm:parse_sdvo_panel_data] Found SDVO panel mode in BIOS VBT tables:
[drm:drm_mode_debug_printmodeline] Modeline 0:"1600x1200" 0 162000 1600 1664
1856 2160 1200 1201 1204 1250 0x8 0xa
[drm:parse_sdvo_device_mapping] No SDVO device info is found in VBT
[drm:parse_driver_features] DRRS State Enabled:1
[drm:parse_ddi_port] Port A VBT info: DP:1 HDMI:0 DVI:0 EDP:1 CRT:0
[drm:parse_ddi_port] VBT HDMI level shift for port A: 0
[drm:parse_ddi_port] Port B VBT info: DP:1 HDMI:1 DVI:1 EDP:0 CRT:0
[drm:parse_ddi_port] VBT HDMI level shift for port B: 2
[drm:parse_ddi_port] Port C VBT info: DP:1 HDMI:1 DVI:1 EDP:0 CRT:0
[drm:parse_ddi_port] VBT HDMI level shift for port C: 13
[drm:intel_dsm_pci_probe] no _DSM method for intel device
[drm:i915_gem_init_stolen] Memory reserved for graphics device: 32768K, usable:
31744K
[drm:intel_power_well_enable] enabling always-on</pre>
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