Probably related: https://patchwork.kernel.org/patch/9716467/
Since the introduction of kernel 4.8 I've been experiencing color banding on my Lenovo G50-80 notebook. I also had reports of the same symptoms on the G50-70 model. I figured out that the problem had been introduced by commit 210a021dab639694600450c14b877bf3e3240adc The G50-80's LCD panel supports 6bpc, but is now set to 8bpc, and the system probably falls back to 6bpc without any dithering, which result in heavily banded gradients. I fixed it for myself by adding an EDID quirk for that particular LCD panel (see the attached patch). It's unknown to me, however, if there are any other panels affected by the issue, so maybe a more general solution might be desirable. diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index fad3d44e4642..ee3124bcae87 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -147,6 +147,9 @@ static const struct edid_quirk { /* Medion MD 30217 PG */ { "MED", 0x7b8, EDID_QUIRK_PREFER_LARGE_75 }, + /* Fix for Lenovo G50 */ + { "SDC", 18514, EDID_QUIRK_FORCE_6BPC }, + /* Panel in Samsung NP700G7A-S01PL notebook reports 6bpc */ { "SEC", 0xd033, EDID_QUIRK_FORCE_8BPC }, ** Tags added: banding bionic color edid i915 lenovo-g50 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1819968 Title: Colour banding in Lenovo G50-80 laptop display (i915) Status in linux package in Ubuntu: Incomplete Bug description: Colour bandind is visible everywhere in the system. I believe it's not a hardware problem, since booting with 'nomodeset' works as expected and the previously installed Ubuntu 14.04 also worked. I tried installing kernel 4.18.0-16.17 from ppa:canonical-kernel- team/ppa but the problem remained. There were already similar bugs, https://bugs.launchpad.net/bugs/1749420 , https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1794387 and https://bugs.launchpad.net/bugs/1788308, but the fixes provided for those bugs did not work for my specific monitor. cat /proc/version_signature Ubuntu 4.15.0-46.49-generic 4.15.18 sudo lspci -vnvn 00:00.0 Host bridge [0600]: Intel Corporation Haswell-ULT DRAM Controller [8086:0a04] (rev 0b) Subsystem: Lenovo Haswell-ULT DRAM Controller [17aa:390b] Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+ >SERR- <PERR- INTx- Latency: 0 Capabilities: [e0] Vendor Specific Information: Len=0c <?> Kernel driver in use: hsw_uncore 00:02.0 VGA compatible controller [0300]: Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 0b) (prog-if 00 [VGA controller]) Subsystem: Lenovo Haswell-ULT Integrated Graphics Controller [17aa:390b] Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+ Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- Latency: 0 Interrupt: pin A routed to IRQ 46 Region 0: Memory at b0000000 (64-bit, non-prefetchable) [size=4M] Region 2: Memory at a0000000 (64-bit, prefetchable) [size=256M] Region 4: I/O ports at 4000 [size=64] [virtual] Expansion ROM at 000c0000 [disabled] [size=128K] Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit- Address: fee02004 Data: 4023 Capabilities: [d0] Power Management version 2 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-) Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME- Capabilities: [a4] PCI Advanced Features AFCap: TP+ FLR+ AFCtrl: FLR- AFStatus: TP- Kernel driver in use: i915 Kernel modules: i915 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1819968/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp