Hi, On Thu, Nov 27, 2025 at 09:46:07AM +0100, Luca Ceresoli wrote: > Hello Francesco, all, > > On Tue Nov 25, 2025 at 11:38 AM CET, Francesco Dolcini wrote: > > From: Francesco Dolcini <[email protected]> > > > > This reverts commit ad5c6ecef27e ("drm: bridge: ti-sn65dsi83: Add error > > recovery mechanism"). > > > > The reverted commit introduces a regression on Verdin AM62, and > > potentially on more devices, not being able to generate a clock > > that the TI SN65DSI83 PLL can lock to, with the display periodically > > blinking. > > > > Verdin AM62 SoM has a Toshiba TC358778 DPI to DSI bridge, that can be > > connected to an LVDS display over a TI SN65DSI83 bridge. Before this > > change despite the TI SN65DSI83 reporting with a debug print a PLL > > locking error the display was working fine with no visible glitches. > > > > The reasons for this issue was investigated without getting to a final > > conclusion: > > > > - the DPI clock was measure and it is stable/accurate > > - the DSI clock was not possible to measure, but this setup is used > > with other display/bridges with no known issues > > - the DSI clock is configured in continuous mode > > - the actual DSI clock generated from the TC358778 is generate with a > > PLL from a 25MHz reference clock > > - it's not clear why some frequencies are working and some are not, for > > example 50000000, 68750000, 72750000, 75000000 frequencies are fine, > > while 69750000, 71100000, 72500000 are not > > > > Given that the safest approach is to just revert the commit, till a > > proper solution for error recovery that is not introducing regression > > is figured out. > > > > Reported-by: João Paulo Gonçalves <[email protected]> > > Closes: > > https://lore.kernel.org/all/bhkn6hley4xrol5o3ytn343h4unkwsr26p6s6ltcwexnrsjsdx@mgkdf6ztow42/ > > Fixes: ad5c6ecef27e ("drm: bridge: ti-sn65dsi83: Add error recovery > > mechanism") > > Cc: [email protected] > > Signed-off-by: Francesco Dolcini <[email protected]> > > Thanks for having sent this revert patch. > > However after evaluating the overall situation I decided to send a > different patch to address this issue in the short term. The idea is to > just ignore the PLL_UNLOCK error, keeping the existing > structure. Rationale: > > * this sloves the issue for Toradex, based on João's initial report > * there is no evidence of any bugs in the recovery mechanism, it's > just exposing a pre-existing problem that was only producing a > non-fatal dev_err() before > * a full revert would remove error checking for all errors, including > those not creating any issue, thus removing a useful feature > * a full revert would require rewriting patches such as [0] (not a big > deal per se, but see next bullet) > * after patches such as [0] are applied, re-adding the error recovery > mechanism would require another rework, so more work for authors, > reviewers, testers and maintainers
Were are we on this? Both patches work for me, but we need to take a decision. Maxime
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