From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-03.galae.net (smtpout-03.galae.net [185.246.85.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 34175313E02 for ; Mon, 1 Dec 2025 17:40:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.85.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764610855; cv=none; b=GYfQsc1tuGluXW1qpF0rAa+vQ7hgOgRdZY7QNv+916nZCsjum6zomVd8hBi9zrwJgbrq2D/co3/f6bn9Lou45tDuVt/CR13ZoSIAtwAA0KapoWPrxz+juCJ5Q70XRAA7Z/CWMWRYU+ty2pbLHp8t2cOeFRljDKtcvqWdmDdMwx0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764610855; c=relaxed/simple; bh=ZJgcv4I6cPzN5ewPb64u//TiNBozHJSD9tXsZw4/GkY=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Jz00YXkOqC+rOYkXJL/yRR2rLxtqE/mdVRLq+uYw293TEtLqyiBt2ZqlVP7U5ApLxujhamu2NZdG+d3B0+KgMwmzeOO23YrVfA3tnpAdFG+SBNMA3dly+XPxmb3w4oQisfgoERdAz40zREROM6G9SpQlWFkwaqxUGsF3VZbdFIk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=AvW9leFg; arc=none smtp.client-ip=185.246.85.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="AvW9leFg" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-03.galae.net (Postfix) with ESMTPS id 1CB664E419B6; Mon, 1 Dec 2025 17:40:50 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id C655B606BB; Mon, 1 Dec 2025 17:40:49 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 730E711918329; Mon, 1 Dec 2025 18:40:40 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1764610848; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=Ot37QYp52dk/c6cg1uKc5U/w8URSDggHQSTyrflhd14=; b=AvW9leFg8jVl+bXv8jgPKspC4XBtIAppmVqvKhO1reZeykAV+EllsRmw5uwL3QUTUJ4TOn gW8AseHMgE02QMwlEPoLg1lirC4iP/RHX2uUa0PdMiGPFUaDpfVq+cgxAGkwN3p4envMiL haHabee2OpV8mduvN2dlX7OMfdeUziVtK1/FwxJ+OP2BAo4d6PltFOZn/I10NOgE433uc5 uFodZe5R2Yp6NypGObg/xkgpiVXwIEnql/oMSCmIZ2q/H6DTWCF21tLyeZ4jIBG9UzeAiZ 6D9YL2MnAq66j3b1RdTzTd5f1bqXX6K8eRjqFgfczZuMH+SP2lHBj1b370+Gqw== Date: Mon, 1 Dec 2025 18:40:39 +0100 From: Herve Codina To: Maxime Ripard , Francesco Dolcini , =?UTF-8?B?Sm/Do28=?= Paulo =?UTF-8?B?R29uw6dhbHZl?= =?UTF-8?B?cw==?= , Emanuele Ghidoli Cc: Luca Ceresoli , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Francesco Dolcini , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Tomi Valkeinen Subject: Re: [PATCH v1] Revert "drm: bridge: ti-sn65dsi83: Add error recovery mechanism" Message-ID: <20251201184039.79dfe0bb@bootlin.com> In-Reply-To: <20251201-uptight-limpet-of-chivalry-404dff@houat> References: <20251125103900.31750-1-francesco@dolcini.it> <20251201-uptight-limpet-of-chivalry-404dff@houat> Organization: Bootlin X-Mailer: Claws Mail 4.3.1 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 Hi Maxime, On Mon, 1 Dec 2025 17:36:13 +0100 Maxime Ripard wrote: > 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 > > > > > > 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 > > > Closes: https://lore.kernel.org/all/bhkn6hley4xrol5o3ytn343h4unkwsr26p6s6ltcwexnrsjsdx@mgkdf6ztow42/ > > > Fixes: ad5c6ecef27e ("drm: bridge: ti-sn65dsi83: Add error recovery mechanism") > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Francesco Dolcini > > > > 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. > IMHO, Luca's patch [0] is more interesting than this current patch doing a full revert. Indeed, Luca's patch keeps the monitoring active except for cases we known broken. Francesco, Emanuele, João have you had time to test Luca's patch ? [0] https://lore.kernel.org/all/20251127-drm-ti-sn65dsi83-ignore-pll-unlock-v1-1-8a03fdf562e9@bootlin.com/ Best regards, Hervé