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Fri, 29 Nov 2024 07:59:30 GMT Received: from szioemm-lnxbld002.qualcomm.com (10.80.80.8) by nasanex01c.na.qualcomm.com (10.45.79.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Thu, 28 Nov 2024 23:59:23 -0800 From: Xiangxu Yin Date: Fri, 29 Nov 2024 15:57:47 +0800 Subject: [PATCH 7/8] drm/msm/dp: Retry Link Training 2 with lower pattern Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20241129-add-displayport-support-for-qcs615-platform-v1-7-09a4338d93ef@quicinc.com> References: <20241129-add-displayport-support-for-qcs615-platform-v1-0-09a4338d93ef@quicinc.com> In-Reply-To: <20241129-add-displayport-support-for-qcs615-platform-v1-0-09a4338d93ef@quicinc.com> To: Rob Clark , Abhinav Kumar , Dmitry Baryshkov , Sean Paul , Marijn Suijten , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Kuogee Hsieh , Vinod Koul , Kishon Vijay Abraham I , Linus Walleij , Bartosz Golaszewski , , CC: , , , , , , , Xiangxu Yin X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; 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This approach enhances compatibility, particularly addressing issues caused by certain hub configurations. Signed-off-by: Xiangxu Yin --- drivers/gpu/drm/msm/dp/dp_ctrl.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c index 49c8ce9b2d0e57a613e50865be3fe98e814d425a..b1862294cb98c9f756b0108b7670cb42de37bae4 100644 --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c @@ -1220,7 +1220,7 @@ static void msm_dp_ctrl_clear_training_pattern(struct msm_dp_ctrl_private *ctrl) } static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl, - int *training_step) + int *training_step, bool downgrade) { int tries = 0, ret = 0; u8 pattern; @@ -1243,6 +1243,28 @@ static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl, state_ctrl_bit = 2; } + /* + * DP link training uses the highest allowed pattern by default. + * If it fails, the pattern is downgraded to improve cable and monitor compatibility. + */ + if (downgrade) { + switch (pattern) { + case DP_TRAINING_PATTERN_4: + pattern = DP_TRAINING_PATTERN_3; + state_ctrl_bit = 3; + break; + case DP_TRAINING_PATTERN_3: + pattern = DP_TRAINING_PATTERN_2; + state_ctrl_bit = 2; + break; + default: + break; + } + } + + drm_dbg_dp(ctrl->drm_dev, "pattern(%d) state_ctrl_bit(%d) downgrade(%d)\n", + pattern, state_ctrl_bit, downgrade); + ret = msm_dp_catalog_ctrl_set_pattern_state_bit(ctrl->catalog, state_ctrl_bit); if (ret) return ret; @@ -1311,10 +1333,14 @@ static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl, /* print success info as this is a result of user initiated action */ drm_dbg_dp(ctrl->drm_dev, "link training #1 successful\n"); - ret = msm_dp_ctrl_link_train_2(ctrl, training_step); + ret = msm_dp_ctrl_link_train_2(ctrl, training_step, false); if (ret) { - DRM_ERROR("link training #2 failed. ret=%d\n", ret); - goto end; + drm_dbg_dp(ctrl->drm_dev, "link training #2 failed, retry downgrade.\n"); + ret = msm_dp_ctrl_link_train_2(ctrl, training_step, true); + if (ret) { + DRM_ERROR("link training #2 failed. ret=%d\n", ret); + goto end; + } } /* print success info as this is a result of user initiated action */