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[122.58.25.162]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36a7212aa06sm428572a91.3.2026.05.21.23.07.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 May 2026 23:07:28 -0700 (PDT) From: Graham O'Connor To: linux-arm-msm@vger.kernel.org Cc: andersson@kernel.org, konradybcio@kernel.org, robin.clark@oss.qualcomm.com, lumag@kernel.org, abhinav.kumar@linux.dev, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Graham O'Connor Subject: [PATCH 3/6] drm/msm/dp: Limit voltage swing level to 2 for RA620 bridge Date: Fri, 22 May 2026 18:06:42 +1200 Message-ID: <20260522060645.4399-4-graham.oconnor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260522060645.4399-1-graham.oconnor@gmail.com> References: <20260522060645.4399-1-graham.oconnor@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The RA620 DP-to-HDMI bridge used on the Radxa Dragon Q6A does not acknowledge DP link training at voltage swing level 3. The bridge requests maximum voltage swing but never completes link training when the driver attempts level 3, causing HDMI output to fail. Cap DP_TRAIN_LEVEL_MAX at 2 to match the behaviour of the vendor kernel, where link training completes successfully at level 2. This allows the RA620 bridge to establish a stable HDMI connection. Tested on Radxa Dragon Q6A (QCS6490) with RA620 DP-to-HDMI bridge Signed-off-by: Graham O'Connor --- drivers/gpu/drm/msm/dp/dp_link.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/msm/dp/dp_link.h b/drivers/gpu/drm/msm/dp/dp_link.h index 76125e9c0..ff0d8e99d 100644 --- a/drivers/gpu/drm/msm/dp/dp_link.h +++ b/drivers/gpu/drm/msm/dp/dp_link.h @@ -24,7 +24,7 @@ struct msm_dp_link_info { unsigned long capabilities; }; -#define DP_TRAIN_LEVEL_MAX 3 +#define DP_TRAIN_LEVEL_MAX 2 struct msm_dp_link_test_video { u32 test_video_pattern; -- 2.53.0