From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 753EBCD98F0 for ; Sun, 21 Jun 2026 06:51:53 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9F53A10E230; Sun, 21 Jun 2026 06:51:52 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kemnade.info header.i=@kemnade.info header.b="h4IvxKbm"; dkim-atps=neutral Received: from mail.andi.de1.cc (mail.andi.de1.cc [178.238.236.174]) by gabe.freedesktop.org (Postfix) with ESMTPS id A6CD310E230 for ; Sun, 21 Jun 2026 06:51:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kemnade.info; s=20220719; h=References:In-Reply-To:Subject:Cc:To:From: Reply-To:Content-ID:Content-Description; bh=4P63oFqyxvE5wl0PfmAzNnEHPyZnJVNTOK5k5qm2RuY=; t=1782024711; x=1783234311; b=h4IvxKbmdfa0enOPdR9BoOP/LJZkmPOw1NrD3fmBnxMsc1LeuuRf+S8XTEq9BIId4OlRmqDKQcE IO5aC9ciwEDmU7lApHy25CpGajS8AEcDBcZO5+agJyjFoS1c9fj8xzuhrYdXHG25R2fIMhWDFqD+q bO8lZl37Tz6lvVhahthDOcRATZqwWW7Z3JYfZP7biqds9p5Mmbmmo2paZLlhrFgMacrspNEy3ulOT vAnXQnuv1jfRj3nnw5622vwb+OQW88RgnxOSaNjVs5tx+7hWWkPPrdv8wMcNECjv5freJBISqRr28 96v+e5Uvy9WUjm+mudo0DD+p4Y82WLHCwkQQ==; Date: Sun, 21 Jun 2026 08:51:44 +0200 From: Andreas Kemnade To: Tomi Valkeinen Cc: Marek Vasut , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Dave Stevenson Subject: Re: [PATCH v3 08/13] drm/bridge: tc358762: Support VTG Message-ID: <20260621085144.0bb1b96e@kemnade.info> In-Reply-To: <20260513-tc358762-fixes-v3-8-6698b55008b9@ideasonboard.com> References: <20260513-tc358762-fixes-v3-0-6698b55008b9@ideasonboard.com> <20260513-tc358762-fixes-v3-8-6698b55008b9@ideasonboard.com> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; aarch64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Wed, 13 May 2026 16:10:17 +0300 Tomi Valkeinen wrote: > 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. > > Signed-off-by: Tomi Valkeinen Seems to produce beside of HFP the same values as the variant with hard coded values with the same videomode struct value. So this looks sane. So based on that. Reviewed-by: Andreas Kemnade > --- > 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 c5734c4df440..2d9491e8e582 100644 > --- a/drivers/gpu/drm/bridge/tc358762.c > +++ b/drivers/gpu/drm/bridge/tc358762.c > @@ -19,6 +19,7 @@ > #include > > #include