From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 D7FAB478847 for ; Mon, 7 Sep 2026 11:28:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788780522; cv=none; b=CEKUjpxo8JIsdZVOWYrDWiGbhf1TNsgO443WTXXSASBHz07PdLhNvtll8LoBCNCuFRp7mSMA9+IYbQSTL4sdPt3O5a/j/xBHdbuKPpOaQ6k90r/6iimuc7LXDl3x3jYA5bqzBqRAKk7VCx1qPJ2odBV7YKAdYgbrViZCXJVNYxU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788780522; c=relaxed/simple; bh=1Uecn7x6YA7Ongo44LRbcp26WhmtFnehgnKpHJpp28Y=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=s0nj/uaQJfj1ap/11jZURFAA865cAlV5/tlCL2Q/JETU/obFYEx8yBC2JEZ6EYVHWrdXWsJeHICi46LbtLcIx5A92PN5ymgi3iIvTX9FZ5CeAO6rHsnVFGUbfVTYtF/XdCn4cdvMHADpIuDMZ2fFACDuKy5tt+ggzpbp1IgZTRk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=whr/abnM; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="whr/abnM" Received: from [127.0.1.1] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id B11CC157F; Mon, 7 Sep 2026 13:26:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1788780416; bh=1Uecn7x6YA7Ongo44LRbcp26WhmtFnehgnKpHJpp28Y=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=whr/abnMdORYLQaXMiX2K18JB25/YnaIX1qM5+4k/ic8gcJCAFJQxhOk4wy1+PvDV TpGNQvwp5u2Lwug21mjFZal2aUBfSfv6TltCq9vcB9GApwo+/I8Zc2BKG6KQyUz4Xm LRQxaoJcJFaPuP8SoTtUvka1fkfM4wG211xosnZk= From: Tomi Valkeinen Date: Mon, 07 Sep 2026 14:28:03 +0300 Subject: [PATCH v4 08/13] drm/bridge: tc358762: Support VTG 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: 7bit Message-Id: <20260907-tc358762-fixes-v4-8-e3fc3ab5cd83@ideasonboard.com> References: <20260907-tc358762-fixes-v4-0-e3fc3ab5cd83@ideasonboard.com> In-Reply-To: <20260907-tc358762-fixes-v4-0-e3fc3ab5cd83@ideasonboard.com> To: Marek Vasut , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Dave Stevenson , Tomi Valkeinen , Andreas Kemnade X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3465; i=tomi.valkeinen@ideasonboard.com; h=from:subject:message-id; bh=1Uecn7x6YA7Ongo44LRbcp26WhmtFnehgnKpHJpp28Y=; b=owEBbQKS/ZANAwAIAfo9qoy8lh71AcsmYgBqnp/UFyupikbOyZA07F+YrKzgr4yoQoLR/R+f5 8PdpCyneayJAjMEAAEIAB0WIQTEOAw+ll79gQef86f6PaqMvJYe9QUCap6f1AAKCRD6PaqMvJYe 9aVAD/0ftAubH68Fyjusg1gMLmkT1c0Oj8dUGbYSeeRoA/tzqhuAo3PGBvI8glIpQwyL5kbRDY8 oOf1/bss/vwATKsWki0WhNb5trbubUBhEvmwNlLkNjqnE8fNVZMI4I2djOGd1EuAcNOLPZ6Y/+A PE+nHdfXHBtLU0zfgWUbvxncBfk5/GFx7LDiD/x4dWQZ3P9aGjLgXhOCn152DHjymwcoJ5Kb7e4 mBT8u/QqQzWRXJIMgvoPBLfyH3zF9uMd7PmNAWZa9DgywfqynSMIWS5KHaivjxn9ZjgWRggtz9r 9TSkPxkx8DAHGXZw4g5LJLeLQb67HN8lXoBL9foWzJQ3iFt6t/ZmRETTriTtur6KXJOcZkBhJqb 1bsVhsRkjZ1xoRcwK8nLnpcquLwTaPrNeZmGyHERBUAUcvDP7WxAdXDhDoiNjQsYvzUkiAMCIL7 HL8QZxFN/BuKgqFr0ns/niiU9i0xVpRbfgFo26i5ktjItGJiCZqcItYHNweVtNKuH5gRjnXZYcv xc+5/yXb/hWpa8q2LiwJ3mvQIh1cBNxn/37d6scK6cEKErX+LYb8JCHKFnHyUISoB+5JLn6HI/k kzcW5kn/CEAfiwHiGUy72XF+taBe1vn5qEL2vSULyDo9VIaUYLZEf27r2Wy9TE4iF2KLTUsXMLy yZeeC4QzUsj/pMA== X-Developer-Key: i=tomi.valkeinen@ideasonboard.com; a=openpgp; fpr=C4380C3E965EFD81079FF3A7FA3DAA8CBC961EF5 TC358762 can generate the DPI output's timings in two ways, either Video Timings Generator (VTG) on or off: - VTG off: Duplicate the timings coming from the DSI. This requires DSI pulse mode. - VTG on: Sync frame on DSI VSync Start, but the exact output timings are defined in TC358762 registers. This can be used with DSI event/burst mode. We are currently using VTG off in the driver. I observe that the hsync signal, on my HW setup, is not 100% stable with VTG off, and it seems to lengthen by a single clock every now and then. However, it then stabilizes later. To me the DSI input looks solid, but that is more challenging to measure exactly. So I have not found the root cause for this. Turning VTG on removes that instability. As I dont' see any downsides with enabling VTG (and it would allow extending the driver to use event/burst mode in the future), let's always enable the VTG. Reviewed-by: Andreas Kemnade Signed-off-by: Tomi Valkeinen --- drivers/gpu/drm/bridge/tc358762.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/drivers/gpu/drm/bridge/tc358762.c b/drivers/gpu/drm/bridge/tc358762.c index 34f2bfd9977c..797866265b41 100644 --- a/drivers/gpu/drm/bridge/tc358762.c +++ b/drivers/gpu/drm/bridge/tc358762.c @@ -18,6 +18,7 @@ #include #include