From ccda4b7fe50dbf616f1c093871be08fe31fceeb3 Mon Sep 17 00:00:00 2001 From: Baihan Li Date: Wed, 13 Aug 2025 17:42:32 +0800 Subject: [PATCH] drm/hisilicon/hibmc: fix rare monitors cannot display problem [ Upstream commit 9f98b429ba67d430b873e06bcfb90afa22888978 ] In some case, the dp link training success at 8.1Gbps, but the sink's maximum supported rate is less than 8.1G. So change the default 8.1Gbps link rate to the rate that reads from devices' capabilities. Fixes: 54063d86e036 ("drm/hisilicon/hibmc: add dp link moduel in hibmc drivers") Signed-off-by: Baihan Li Signed-off-by: Yongbang Shi Reviewed-by: Dmitry Baryshkov Link: https://lore.kernel.org/r/20250813094238.3722345-6-shiyongbang@huawei.com Signed-off-by: Dmitry Baryshkov Signed-off-by: Sasha Levin --- drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c index 74f7832ea53ea..0726cb5b736e6 100644 --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c @@ -325,6 +325,17 @@ static int hibmc_dp_link_downgrade_training_eq(struct hibmc_dp_dev *dp) return hibmc_dp_link_reduce_rate(dp); } +static void hibmc_dp_update_caps(struct hibmc_dp_dev *dp) +{ + dp->link.cap.link_rate = dp->dpcd[DP_MAX_LINK_RATE]; + if (dp->link.cap.link_rate > DP_LINK_BW_8_1 || !dp->link.cap.link_rate) + dp->link.cap.link_rate = DP_LINK_BW_8_1; + + dp->link.cap.lanes = dp->dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK; + if (dp->link.cap.lanes > HIBMC_DP_LANE_NUM_MAX) + dp->link.cap.lanes = HIBMC_DP_LANE_NUM_MAX; +} + int hibmc_dp_link_training(struct hibmc_dp_dev *dp) { struct hibmc_dp_link *link = &dp->link; @@ -334,8 +345,7 @@ int hibmc_dp_link_training(struct hibmc_dp_dev *dp) if (ret) drm_err(dp->dev, "dp aux read dpcd failed, ret: %d\n", ret); - dp->link.cap.link_rate = dp->dpcd[DP_MAX_LINK_RATE]; - dp->link.cap.lanes = 0x2; + hibmc_dp_update_caps(dp); ret = hibmc_dp_get_serdes_rate_cfg(dp); if (ret < 0) -- 2.47.3