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 4313B10854BE for ; Wed, 18 Mar 2026 08:51:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9FEE810E75C; Wed, 18 Mar 2026 08:51:57 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=bootlin.com header.i=@bootlin.com header.b="cp7fSnBA"; dkim-atps=neutral Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) by gabe.freedesktop.org (Postfix) with ESMTPS id 75F8310E761 for ; Wed, 18 Mar 2026 08:51:55 +0000 (UTC) Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id AA9AE1A2E9F; Wed, 18 Mar 2026 08:51:53 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 7BE096004F; Wed, 18 Mar 2026 08:51:53 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 059E5104506D1; Wed, 18 Mar 2026 09:51:40 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1773823908; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=alSZ2fWiAi+9qwfblfCJyz0fVMs/+X5EwPZ2SQgxmLQ=; b=cp7fSnBAyWP25/Vl+tF6iiCGYoJXIVWSHpR+5L4HAY2v19vJBUA+qoEwIqKJjlYpXVYFKU Yq/xbInLIl8Xv1/Voi2LGVlm/wbox8/Amb44AfhPFY/gmjxrTRpemc4pjxTIQAMnoTLyw2 g/yB36lMoqLyAtZhDQpUwycEQlOiAqtyzbZUifcFFfHQl1LLamw5Gq3anHAcBrrd5KD/TD UGdCu0DPDZUIVaCoYr5e7qCNStyb8YbtIuP9G/SVDOxsz8Fw6mDvQK2W2lA2o+OrgK7dw9 xfvyjQm57SPNyLS8gCsk6D63W1plQhrX2xNGRmpYFwIFl5mw4xP0uyeg54NoGA== Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 18 Mar 2026 09:51:39 +0100 Message-Id: From: "Luca Ceresoli" Subject: Re: [PATCH v2 0/2] drm: bridge: ti-sn65dsi83: Improve dual-link LVDS support Cc: , , , , , , , , , , , , , , , To: , "Marek Vasut" , , , X-Mailer: aerc 0.20.1 References: <20260312043743.261475-1-tessolveupstream@gmail.com> <9f694b2d-44bc-46ad-8aa3-b464c2f0da13@nabladev.com> <176ed865-11a6-42de-89e0-06951b59a430@gmail.com> <49b79a0d-844b-4fee-bccb-706187ed76d1@gmail.com> In-Reply-To: <49b79a0d-844b-4fee-bccb-706187ed76d1@gmail.com> X-Last-TLS-Session-Version: TLSv1.3 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" Hello Sudarshan, On Wed Mar 18, 2026 at 6:45 AM CET, tessolveupstream wrote: >>>> You might want to look at recently posted: >>>> >>>> [PATCH 2/3] drm/bridge: ti-sn65dsi83: halve horizontal syncs for dual = LVDS output >>> >>> Thanks for pointing this out. >>> I tried applying the patch =E2=80=9C[PATCH 2/3] drm/bridge: ti-sn65dsi8= 3: halve horizontal syncs for dual LVDS output=E2=80=9D on top of the curre= nt tree and >>> removed the changes that I had previously added in the driver. >>> However, with this patch applied, I am currently seeing only the backli= ght turning on and no image on the LVDS panel. >>> For reference, the LVDS panel used on our platform is G133HAN01.1 and t= he >>> DSI-to-dual-link LVDS bridge is SN65DSI84ZXHR. >> >> Thanks for having tried. >> >> Can you please test with both the fixes in the series applied + the test >> pattern feature and report the results you get with and without test >> pattern enabled? >> >> The patches to apply are: >> >> - https://lore.kernel.org/all/20260226-ti-sn65dsi83-dual-lvds-fixes-and= -test-pattern-v1-1-2e15f5a9a6a0@bootlin.com/ >> - https://lore.kernel.org/all/20260226-ti-sn65dsi83-dual-lvds-fixes-and= -test-pattern-v1-2-2e15f5a9a6a0@bootlin.com/ >> - https://lore.kernel.org/lkml/20260309-ti-sn65dsi83-dual-lvds-fixes-an= d-test-pattern-v2-1-e6aaa7e1d181@bootlin.com/ >> > > Thanks for the suggestions. > > I tested the three patches together as mentioned, but the LVDS panel > still only shows the backlight and no image. I also tried removing the > test-pattern patch and retesting with only the remaining two fixes, but > the result remained the same =E2=80=94 only the backlight turns on and no= image > is displayed. Sure, the test pattern patch does not change anything, unless you enable the test pattern. >> The first thing I suggest doing on your side is testing with the 3 patch= es >> mentioned above. >> >> If you display works, good! Let us know (you can also add your Tested-by= / >> Reviewed-by tags to the test_pattern patch too if applicable). >> >> If it doesn't work, compare the individual register values to find the >> differences, try to figure out why the working setting works and how to >> apply that change to the driver in away that keeps other boards >> working. You're welcome to come back here to discuss it in case you can'= t >> find out on your own. >> > > I tested the three patches as suggested, but the panel still shows only t= he > backlight with no visible image. I=E2=80=99m unsure how to translate the = working > register values into a generic fix based on display timings. Any guidance > on the right direction would be helpful. What you should do is: 1. with your patches, and while the display is enabled (and working) do cat /sys/kernel/debug/regmap/4-002c/registers >regs.working 2. remove your patches, add the 3 I mentioned, and while the display is enabled (but only backlight is working) do cat /sys/kernel/debug/regmap/4-002c/registers >regs.broken Then compare regs.working and regs.broken. Which registers differ? Can you give a reason for the differences? You can come back with these values here so we may discuss them. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com