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Tue, 07 Jul 2026 12:38:24 +0200 (CEST) Message-ID: <6fed12a6-0c94-477f-8a2e-466c33ea2e29@collabora.com> Date: Tue, 7 Jul 2026 12:38:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/mediatek: mtk_dsi: enable hs clock during pre-enable To: Thorsten Leemhuis , =?UTF-8?B?Q0sgSHUgKOiDoeS/iuWFiSk=?= , "me@adamthiede.com" , "bisson.gary@gmail.com" Cc: "chunkuang.hu@kernel.org" , "simona@ffwll.ch" , "dri-devel@lists.freedesktop.org" , "airlied@gmail.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "p.zabel@pengutronix.de" , "matthias.bgg@gmail.com" , "linux-mediatek@lists.infradead.org" , "regressions@lists.linux.dev" References: <20260120-mtkdsi-v1-1-b0f4094f3ac3@gmail.com> <42607fa4-485d-4142-b31c-7bfac71118d2@adamthiede.com> <5baeb90d2c3736df67ad075ede4ac765bfeaed2d.camel@mediatek.com> <84233951-ee22-4980-9f17-2af1df51fdbf@leemhuis.info> From: AngeloGioacchino Del Regno Content-Language: en-US In-Reply-To: <84233951-ee22-4980-9f17-2af1df51fdbf@leemhuis.info> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260707_033827_257287_9E5B86CC X-CRM114-Status: GOOD ( 28.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/7/26 10:51, Thorsten Leemhuis wrote: > On 7/7/26 04:20, CK Hu (胡俊光) wrote: >> On Mon, 2026-07-06 at 12:16 +0200, Thorsten Leemhuis wrote: >>> On 6/22/26 15:23, Adam Thiede wrote: >>>> On 6/22/26 06:22, Gary Bisson wrote: >>>>> On Thu, Jun 18, 2026 at 04:06:28PM -0500, Adam Thiede wrote: >>>>>> On 1/20/26 05:36, Gary Bisson wrote: >>>>>>> Some bridges, such as the TI SN65DSI83, require the HS clock to be >>>>>>> running in order to lock its PLL during its own pre-enable function. >>>>>>> >>>>>>> Without this change, the bridge gives the following error: >>>>>>> sn65dsi83 14-002c: failed to lock PLL, ret=-110 >>>>>>> sn65dsi83 14-002c: Unexpected link status 0x01 >>>>>>> sn65dsi83 14-002c: reset the pipe >>>>>>> [...] >>>>>> >>>>>> This commit was part of 7.1 and caused a problem for me. >>>>>> I'm running postmarketOS (basically Alpine Linux) on a Lenovo C330 >>>>>> chromebook with a Mediatek MT8173 processor. >>>>>> The problem: when the display on my laptop powers off (via suspend or >>>>>> idle, >>>>>> like xset dpms off) the picture does not come back when the display >>>>>> powers >>>>>> back on (from resume). The display backlight comes on and brightness is >>>>>> adjustable but there is no picture. The only fix is to reboot. >>>>>> >>>>>> Reverting this commit and applying it as a patch on top of 7.1 >>>>>> addresses the >>>>>> issue for me. >>>>>> >>>>>> You can view the config I'm using here: >>>>>> https://urldefense.com/v3/__https://gitlab.postmarketos.org/postmarketOS/pmaports/-/__;!!CTRNKA9wMg0ARbw!jrsPDtSEUdaINzLlq92Li8gmsEBkTOxZ6WUzNHjvIN6CyOJjHiHkNSOhIRPXFTLPlaYlxU2uvryVkwjUAN9bmax5$ >>>>>> merge_requests/8819 >>>>>> >>>>>> Is there any sort of testing or other debugging info I can provide to >>>>>> help >>>>>> address this issue? >>>>> >>>>> Thanks for reporting the issue, could you share some logs? Is the driver >>>>> saying anything during resume? Also, what type of panel is used on that >>>>> chromebook? >>>> >>>> The curious thing is that there are no real logs in dmesg or /var/log/ >>>> messages about this. This picture just fails to come back. If there are >>>> some kernel params I can set to get deeper logging, that would help, but >>>> I'm not aware of any. >>>> >>>> I think the panel is a "BOE NV116WHM-T00" - I used this command to get >>>> info: cat /sys/class/drm/card0-eDP-1/edid | edid-decode >>>> >>>> Output: https://urldefense.com/v3/__https://termbin.com/8nbd__;!!CTRNKA9wMg0ARbw!jrsPDtSEUdaINzLlq92Li8gmsEBkTOxZ6WUzNHjvIN6CyOJjHiHkNSOhIRPXFTLPlaYlxU2uvryVkwjUAJooSyqL$ >>> >>> This looked stalled. If I'm mistaken here, please let me known; but if >>> no solution is in sight, should we maybe just revert the change until a >>> proper was found? >> >> It's welcome anyone to provide a revert patch, >> but I would still wait for the fixup patch until 7.2-rc4. >> If no fixup patch exist, then apply the revert patch. > From my understanding of things the position in the devel cycle doesn't > matter much in a case like this. To quote Linus statements from > https://www.kernel.org/doc/html/latest/process/handling-regressions.html#on-how-quickly-regressions-should-be-fixed > > """ > From 2026-01-22: > > But a user complaining should basically result in an immediate fix - > possibly a "revert and rethink". > > With a later clarification on 2026-01-28: > > It's also worth noting that "immediate" obviously doesn't mean "right > this *second* when the problem has been reported". > > But if it's a regression with a known commit that caused it, I think > the rule of thumb should generally be "within a week", preferably > before the next rc. > """ > > Adam reported the problem about three weeks ago, so we are way past the > "rule of thumb" timeframe Linus set. > > Ciao, Thorsten This is a kind of odd situation here. The fix from Adam is actually correct, as in, the SN65DSI83 bridge gets broken without... ....but then, there's some more oddness going on: I tried to reproduce this on my MT8173 Elm device, but there I can resume the system just fine, and the display is up and running like normal? I'm not sure what to advice here at this point - just adding some info. Cheers, Angelo