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Mon, 20 Apr 2026 23:02:06 -0700 (PDT) Received: from [172.16.20.13] ([136.226.252.245]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8e9fbb85sm14768763b3a.22.2026.04.20.23.01.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Apr 2026 23:02:05 -0700 (PDT) Message-ID: <7056b23b-ed81-4d79-b782-5cfcb0102ef7@gmail.com> Date: Tue, 21 Apr 2026 11:31:57 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/1] drm: bridge: ti-sn65dsi83: Fix DSI mode flags for stable LVDS output From: tessolveupstream@gmail.com To: Luca Ceresoli , andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org Cc: Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, marex@denx.de, valentin@compulab.co.il, philippe.schenker@toradex.com, alexander.stein@ew.tq-group.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260412053811.662461-1-tessolveupstream@gmail.com> <20260412053811.662461-2-tessolveupstream@gmail.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 16-04-2026 14:40, tessolveupstream@gmail.com wrote: > > > On 15-04-2026 12:43, 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 for >> the removal of these three flags. >> >> It would be still great to have authoritative info from TI, possibly as an >> update to the documentation. >> >> I managed to test on a board with i.MX93, a TI SN65DSI84 and a 1920x1080p60 >> 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 >> > > Thanks for testing the patch and for the Tested-by tag. > I’ll reach out to TI for clarification on the DSI mode flag behavior and > any documentation updates, and will share any feedback I receive, though I > cannot guarantee a response. I had reached out to TI for clarification and any related documentation updates, but I have not received any response so far.Given this, it is uncertain whether we will be able to obtain further details or official confirmation from TI in the near term. I would appreciate your guidance on how you would prefer us to proceed from here. >> Luca >> >> -- >> Luca Ceresoli, Bootlin >> Embedded Linux and Kernel engineering >> https://bootlin.com >