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[143.177.148.84]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64b91599844sm7577559a12.25.2025.12.21.08.15.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 21 Dec 2025 08:15:17 -0800 (PST) Message-ID: Date: Sun, 21 Dec 2025 17:15:17 +0100 Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/tegra: Enable cmu for Tegra186 and Tegra194 From: Jasper Korten To: Aaron Kling Cc: Thierry Reding , Mikko Perttunen , David Airlie , Simona Vetter , Jonathan Hunter , dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251101-tegra-drm-cmu-v1-1-211799755ab8@gmail.com> <72llskwvuwyllvz24zoex4ad6v6t5skiehmwylj7exoh7bmzjo@xq3v7vja5w62> <6dc26bf0-6e28-4478-9ec4-20622cc8a19e@gmail.com> Content-Language: en-US In-Reply-To: <6dc26bf0-6e28-4478-9ec4-20622cc8a19e@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 18/12/2025 00:18, Jasper Korten wrote: > On 09/12/2025 05:23, Aaron Kling wrote: > >> On Wed, Nov 5, 2025 at 3:28 PM Jasper Korten wrote: >>> Hi all, >>> >>> On 11/4/25 19:12, Aaron Kling wrote: >>>> On Tue, Nov 4, 2025 at 3:14 AM Thierry Reding >>>> wrote: >>>>> On Mon, Nov 03, 2025 at 12:39:57PM -0600, Aaron Kling wrote: >>>>>> On Mon, Nov 3, 2025 at 5:54 AM Thierry Reding >>>>>> wrote: >>>>>>> On Sat, Nov 01, 2025 at 06:15:17PM -0500, Aaron Kling via B4 >>>>>>> Relay wrote: >>>>>>>> From: Aaron Kling >>>>>>>> >>>>>>>> Without the cmu, nvdisplay will display colors that are notably >>>>>>>> darker >>>>>>>> than intended. The vendor bootloader and the downstream display >>>>>>>> driver >>>>>>>> enable the cmu and sets a sRGB table. Loading that table here >>>>>>>> results in >>>>>>>> the intended colors. >>>>>>>> >>>>>>>> Signed-off-by: Aaron Kling >>>>>>>> --- >>>>>>>>    drivers/gpu/drm/tegra/dc.h  |  13 +++ >>>>>>>>    drivers/gpu/drm/tegra/sor.c | 206 >>>>>>>> ++++++++++++++++++++++++++++++++++++++++++++ >>>>>>>>    2 files changed, 219 insertions(+) >>>>>>> What does "darker than intended" mean? Who defines the >>>>>>> intention? How do >>>>>>> we know what the intention is? What this patch ultimately seems >>>>>>> to be >>>>>>> doing is define sRGB to be the default colorspace. Is that >>>>>>> always the >>>>>>> right default choice? What if people want to specify a different >>>>>>> colorspace? >>>>>> I reported this issue almost a month ago. See kernel lore [0] and >>>>>> freedesktop issue [1]. The pictures in the latter show what >>>>>> nvdisplay >>>>>> looks like right now. It's nigh unusably dark. When booted into >>>>>> Android with a tv launcher that has a black background, as is >>>>>> default >>>>>> for LineageOS, it is really hard to read anything. Is it correct >>>>>> as a >>>>>> default? Well, cboot hardcodes this, so... presumably? It would be >>>>>> more ideal to expose this and csc to userspace, but I'm not sure if >>>>>> drm has a standardized interface for that or if tegra would have to >>>>>> make something vendor specific. I think that would be a separate >>>>>> change concept compared to setting this default, though. >>>>> The reason I'm asking is because I don't recall ever seeing "broken" >>>>> colors like you do. So I suspect that this may also be related to >>>>> what >>>>> display is connected, or the mode that we're setting. >>> I have tried it on both a MacroSilicon HDMI capture card and an Arzopa >>> Z1FC 1080p portable monitor and run into the same darker colors. Both >>> have in common that they use HDMI which seems to line up with what >>> Aaron >>> is reporting. I do not have an eDP display to test or another carrier >>> board with a different display out to test. >>>>> It could perhaps >>>>> also be related to what infoframes we're sending and how these are >>>>> supported/interpreted by the attached display. >>>>> >>>>> All of that is to say that maybe this looks broken on the particular >>>>> setup that you have but may works fine on other setups. Changing the >>>>> default may fix your setup and break others. >>>> Do you have a device set up so you can check? Or does the regression >>>> test bench have a display that can be forwarded? >>>> >>>> My current setup is a rack of units plugged via hdmi to a kvm which is >>>> then plugged to a pikvm. I also observed this issue before I had this >>>> setup, plugged directly to a 1080p monitor. I have not checked >>>> displayport. I can cycle through a couple other displays without this >>>> patch to see if I get any other result. I am fairly certain I have >>>> consistently seen this issue since I started trying to work with >>>> tegra-drm on kernel 6.1 or maybe even 5.15. I've never seen it work to >>>> allow for a bisect. >>>> >>>> I am in contact with one other person with a tx2 devkit, who >>>> replicated the issue when I asked. Who plans to reply to this thread >>>> with setup info later. >>> For reference, I am said person. I have a Jetson TX2 Devkit that uses >>> the P2771 Device Tree. I'm running a Fedora distrokernel with no >>> additional patches applied by myself. I have personally noticed the >>> issue to at least be present on 6.14.5 and 6.17.4. >>> >>> >>> I'm currently not at home to take screenshots with and without the >>> submitted patch, but will be able to do it tomorrownight or friday. >> Any further thoughts from the maintainers on this patch? As far as I >> know, this is an issue for all users, at the very least on hdmi. >> >> Aaron > > I've finally captured some footage of the colors of my TX2 within tty. > I've also added a reference in the form of my X13s doing the same > thing.[1] > > I will at a later date try the patch and update the MR comment, > but at least this shows the difference while recording using the same > setup. > > Kindest regards, > > Jasper > > [1]: https://gitlab.freedesktop.org/drm/tegra/-/issues/8#note_3242611 > As promised, I've added my test results to the Issue[1]. It seems to improve colors a lot more, haven't ran into any other issues. The patch seems to work therefore: Tested-by: Jasper Korten Kindest regards, Jasper Korten [1]: https://gitlab.freedesktop.org/drm/tegra/-/issues/8#note_3246713