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[143.177.148.84]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64b5886d434sm760731a12.21.2025.12.17.15.18.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Dec 2025 15:18:16 -0800 (PST) Message-ID: <6dc26bf0-6e28-4478-9ec4-20622cc8a19e@gmail.com> Date: Thu, 18 Dec 2025 00:18:18 +0100 Precedence: bulk X-Mailing-List: linux-kernel@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 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> Content-Language: en-US From: Jasper Korten In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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