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Tue, 10 Nov 2026 05:15:33 -0800 (PST) Received: from desktop.home ([46.205.207.69]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6b75790353asm1126372a12.31.2026.11.10.05.15.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 05:15:33 -0800 (PST) From: =?UTF-8?q?Andrzej=20Pi=C4=85tyszek?= To: amd-gfx@lists.freedesktop.org Cc: Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , =?UTF-8?q?Christian=20K=C3=B6nig?= , Fangzhi Zuo , Relja Vojvodic , Ilya Bakoulin , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, =?UTF-8?q?Andrzej=20Pi=C4=85tyszek?= Subject: [PATCH 2/3] drm/amd/display: Wait up to 1 s for slow sinks in FRL link training Date: Tue, 10 Nov 2026 14:09:55 +0100 Message-ID: <20261110130956.160024-3-andrzej.piatyszek@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261110130956.160024-1-andrzej.piatyszek@gmail.com> References: <20261110130956.160024-1-andrzej.piatyszek@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit LTS:3 gives the sink 220 ms (320 ms at 16 Gbps and above) to answer an LTP request before the driver gives up on the rate. A Samsung QE65Q80T (2020) sometimes answers at 10 Gbps x 4 only after 225 to 967 ms, so link verification falls back to 6 Gbps x 3. Wait up to 1 s at every rate. Sinks that answer within the old limit are unaffected; a sink that never answers costs up to 1 s per rate in the polling loop instead of 220 ms. Fixes: cbb8e2044b9e ("drm/amd/display: Add DC link support for FRL") Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Andrzej Piątyszek --- .../drm/amd/display/dc/link/protocols/link_hdmi_frl.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_hdmi_frl.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_hdmi_frl.c index 78e62bfec..97b2b9b74 100644 --- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_hdmi_frl.c +++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_hdmi_frl.c @@ -612,10 +612,13 @@ static enum link_result hdmi_frl_perform_link_training(struct ddc_service *ddc_s FRL_INFO("FRL LINK TRAINING: Poll for FLT_UPDATE.\n"); /*LTS:3: Start Link Training*/ - /*Start FLT Timer = 200 ms, or 300ms if link rate >= 16Gbps*/ + /* + * Start FLT Timer. Some sinks need longer than the nominal 200 ms + * (300 ms at 16 Gbps and above) to answer an LTP request, so wait + * up to 1 s before giving up on this rate. + */ num_polls = 0; - if (link_settings->frl_link_rate >= HDMI_FRL_LINK_RATE_16GBPS) - poll_timeout_ns = 320 * 1000 * 1000; + poll_timeout_ns = 1000 * 1000 * 1000; flt_poll_start = dm_get_timestamp(ddc_service->ctx); uint8_t prev_flt_update = 0; -- 2.56.0