From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (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 B8B4539EF30 for ; Wed, 15 Apr 2026 08:07:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776240464; cv=none; b=jAidpTG28/NTPc6atD19piu/5sEAR7uszJUCqI6CZ1OIaNG1EpSGWGHssrsiYyTjrVOOwQIImlI9G+p/XUaEvOAy3zurnZsOYzj4p/SZQIysJMtmcPdiG3Pc1Y57CgY7dn1SY+XuVlXPLNbx23i1OBjYXOFifCeTK8uqf/iCddg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776240464; c=relaxed/simple; bh=G2BuYglCxNNM5pN0uBSE6sK8eTk0+fRpuk4CphDvlk8=; h=Mime-Version:Content-Type:Date:Message-Id:Subject:Cc:To:From: References:In-Reply-To; b=cfPva1XPnyFK7fJBtpIP5/2ow8sZ9aqrdQE3w9Kb6ITrFVZtN8WwJ9AMF5kf5RXUVbbPQwINTJMBgr8kxPY7EC6t2jXUUwyQOOf39a0vsUlWp5M1+bI3AU70lPx+EWGuiLbYZXDtBIHP1NVXdv7zy+ZPQQAJmIC+3TESTbnQp0s= 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=PwmHiPX+; arc=none smtp.client-ip=185.171.202.116 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="PwmHiPX+" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 711A6C5AABF; Wed, 15 Apr 2026 08:08:17 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id CCCB660420; Wed, 15 Apr 2026 08:07:39 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 5417510451BC2; Wed, 15 Apr 2026 10:07:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1776240458; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=cSY2tIyXcuZuOelcL3Cqr3aN8E+YxAI8Sm5cELy+gE8=; b=PwmHiPX+F8ofsnKYyNtXxrLCvlu/Fj31sxBhVXJX8vXTEVm1EliSp8nsaTchrDtR0aaP9S XerBnyaldACNW9+VirY2vZycQpoIwUO3tTc+uXg+ihrTY2H6RXoPj2Xf+0e9hRpwOuHlHH EZlaONrjIoP/WzH3voEODKKDp8h54nxzVi9CJbCC/ORfK2RT+T2/w7a7distYC1eUPndeD bAvvSE5P4YD0k7B7zcNYKYG4gGKkVd0ot4QHufH4mv8iO/JVwr9kuIIgRbNba7W71LRD7L yG8UOj6tJn7C4DibnGkg5sMmgm9K5xL3oSzCgRsFcDSJx4A2FIcASRiDArJMzQ== Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 15 Apr 2026 10:07:32 +0200 Message-Id: Subject: Re: [PATCH v3 1/1] drm: bridge: ti-sn65dsi83: Fix DSI mode flags for stable LVDS output Cc: , , , , , , , , , , , , , To: "Luca Ceresoli" , "Sudarshan Shetty" , , , From: "Luca Ceresoli" X-Mailer: aerc 0.20.1 References: <20260412053811.662461-1-tessolveupstream@gmail.com> <20260412053811.662461-2-tessolveupstream@gmail.com> In-Reply-To: X-Last-TLS-Session-Version: TLSv1.3 On Wed Apr 15, 2026 at 9:13 AM CEST, Luca Ceresoli wrote: > Hello Sudarshan, > > On Sun Apr 12, 2026 at 7:38 AM CEST, Sudarshan Shetty wrote: >> The current DSI mode configuration enables VIDEO_BURST and disables >> horizontal front porch (HFP) and back porch (HBP) transmission using >> MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP. >> >> However, the SN65DSI83/84 bridge relies on receiving full horizontal >> timing information over DSI in order to correctly reconstruct the LVDS >> output timings. When HFP and HBP are not transmitted, the bridge cannot >> recreate the required timing parameters, resulting in unstable or >> missing display output on some panels. >> >> Additionally, while burst mode is supported by the hardware, its use >> depends on continuous clock behavior from the DSI host. In practice, >> burst mode may introduce instability depending on the host controller >> implementation, as the DSI link may transition to low-power state >> between bursts. >> >> In testing, removing burst mode and ensuring full horizontal timing >> transmission results in stable LVDS output across affected panels. >> >> Update the DSI mode flags to: >> - Drop MIPI_DSI_MODE_VIDEO_BURST >> - Drop MIPI_DSI_MODE_VIDEO_NO_HFP >> - Drop MIPI_DSI_MODE_VIDEO_NO_HBP >> >> This aligns with common system configurations where non-burst mode is >> preferred and full timing information is transmitted over DSI. >> >> Signed-off-by: Sudarshan Shetty > > Thanks for having gone into the details and provide a good explanation fo= r > the removal of these three flags. > > It would be still great to have authoritative info from TI, possibly as a= n > update to the documentation. > > I managed to test on a board with i.MX93, a TI SN65DSI84 and a 1920x1080p= 60 > panel, and: > > - no image shown with the current mainline driver > - it works by removing only MIPI_DSI_MODE_VIDEO_BURST (my current setup) > - it works with this patch applied > > Tested-by: Luca Ceresoli # imx93 1920x1080p60 And tested on a i.MX8MP board too, with a different 1920x1080p60 panel. This one was working without the patch and is equally working with the patch applied. Tested-by: Luca Ceresoli # imx8mp 1920x1080p60 Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com