Wait a minute... it sounds like dithering is always going to be disabled (since commit 611032bfa71a7) for the case of (pipe_config->pipe_bpp == 6*3).
index 5a9da484bb23..ef65b4be5e56 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -13060,8 +13060,11 @@ intel_modeset_pipe_config(struct drm_crtc *crtc, } /* Dithering seems to not pass-through bits correctly when it should, so - * only enable it on 6bpc panels. */ - pipe_config->dither = pipe_config->pipe_bpp == 6*3; + * only enable it on 6bpc panels and when its not a compliance + * test requesting 6bpc video pattern. + */ + pipe_config->dither = (pipe_config->pipe_bpp == 6*3) && + !pipe_config->dither_force_disable; DRM_DEBUG_KMS("hw max bpp: %i, pipe bpp: %i, dithering: %i\n", base_bpp, pipe_config->pipe_bpp, pipe_config->dither); diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index e245802c5727..0fafbec6dacf 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -28,8 +28,10 @@ #include <linux/i2c.h> #include <linux/slab.h> #include <linux/export.h> +#include <linux/types.h> #include <linux/notifier.h> #include <linux/reboot.h> +#include <asm/byteorder.h> #include <drm/drmP.h> #include <drm/drm_atomic_helper.h> #include <drm/drm_crtc.h> @@ -1593,6 +1595,13 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp, if (bpc > 0) bpp = min(bpp, 3*bpc); + /* For DP Compliance we override the computed bpp for the pipe */ + if (intel_dp->compliance.test_data.bpc != 0) { + pipe_config->pipe_bpp = 3*intel_dp->compliance.test_data.bpc; + pipe_config->dither_force_disable = pipe_config->pipe_bpp == 6*3; + DRM_DEBUG_KMS("Setting pipe_bpp to %d\n", + pipe_config->pipe_bpp); + } return bpp; } -- 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/1749420 Title: Colour banding and artefacts appear system-wide on an Asus Zenbook UX303LA with Intel HD 4400 graphics Status in linux package in Ubuntu: Confirmed Bug description: - Ubuntu 18.04 (with updates as of 14 Feb 2018). - Laptop: Asus Zenbook UX303 - CPU: Intel i5 4210U - Graphics: Intel HD 4400 Problem description: Colour artefacts and banding in all apps. Graphics, photos and videos display as though the colour range is improperly configured. See this photo of a 1080p video taken with a camera (poor quality, but illustrates the issue): https://ubuntucommunity.s3-us- east-2.amazonaws.com/original/2X/c/c8f266715226953c6a77db6367ff9b7895784e35.jpg Look at the sky’s light colours. They display with smooth gradients on Ubuntu 16.04, but as the photo illustrates 18.04 seems to display the video with a smaller range of white colours. This is the most apparent with either very dark or very light colours. Even on window titlebars the banding is visible (displayed as lines with different shades of grey/black). Compared with a PrtSc shot of the same image: https://i.imgur.com/VkOSCaQ.png The artefacts are not present on PrtSc shots that are taken on Ubuntu 18.04 but viewed on a different system (16.04 and Windows). Installing a previous kernel version fixes the issue completely. I used UKUU Update Utility to install kernel 4.4 (the same that I use in Ubuntu 16.04 without issues) and upon a reboot with 4.4 running on 18.04 everything displayed smoothly. So this indicates that the system might be using a sub-optimal colour depth with the newer kernel? ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: linux-image-4.13.0-32-generic 4.13.0-32.35 [modified: boot/vmlinuz-4.13.0-32-generic] ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13 Uname: Linux 4.13.0-32-generic x86_64 ApportVersion: 2.20.8-0ubuntu10 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: ystein 1344 F.... pulseaudio /dev/snd/controlC1: ystein 1344 F.... pulseaudio CurrentDesktop: ubuntu:GNOME Date: Wed Feb 14 11:25:43 2018 EcryptfsInUse: Yes HibernationDevice: RESUME=UUID=d0bae648-a4d8-454c-b9fc-4cc04874d6c1 InstallationDate: Installed on 2018-02-12 (1 days ago) InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180210) Lsusb: Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 004: ID 8087:07dc Intel Corp. Bus 001 Device 003: ID 064e:9700 Suyin Corp. Asus Integrated Webcam Bus 001 Device 002: ID 046d:c52b Logitech, Inc. Unifying Receiver Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub MachineType: ASUSTeK COMPUTER INC. UX303LA ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-32-generic.efi.signed root=UUID=25279d7b-cc8a-4fee-9088-cfc69607cbca ro quiet splash vt.handoff=1 RelatedPackageVersions: linux-restricted-modules-4.13.0-32-generic N/A linux-backports-modules-4.13.0-32-generic N/A linux-firmware 1.170 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 09/01/2014 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: UX303LA.204 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: UX303LA dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX303LA.204:bd09/01/2014:svnASUSTeKCOMPUTERINC.:pnUX303LA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX303LA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.family: UX dmi.product.name: UX303LA dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. 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