linux-kernel - Re: [PATCH v10 drm-dp 1/4] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq

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Message-ID: <d6otacjtio25alb2stjscl47xkq7lhexmciuiuot3pk5x4hcqd@tq7ckfvnd6oy>
Date: Tue, 20 Jan 2026 10:51:52 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yongbang Shi <shiyongbang@...wei.com>
Cc: xinliang.liu@...aro.org, tiantao6@...ilicon.com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        kong.kongxinwei@...ilicon.com, liangjian010@...wei.com,
        chenjianmin@...wei.com, fengsheng5@...wei.com, libaihan@...wei.com,
        shenjian15@...wei.com, shaojijie@...wei.com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 drm-dp 1/4] drm/hisilicon/hibmc: fix dp
 probabilistical detect errors after HPD irq

On Wed, Dec 10, 2025 at 10:37:56AM +0800, Yongbang Shi wrote:
> From: Baihan Li <libaihan@...wei.com>
> 
> The issue is that drm_connector_helper_detect_from_ddc() returns wrong
> status when plugging or unplugging the monitor, which may cause the link
> failed err.[0] Use HPD pin status in DP's detect_ctx() for real physical
> monitor in/out, and implement a complete DP detection including read DPCD,
> check if it's a branch device and its sink count for different situations.
> 
> [0]:
> 	hibme-drm 0000:83:00.0: [drm] *ERROR* channel equalization failed 5 times
> 	hibme-drm 0000:83:00.0: [drm] *ERROR* channel equalization failed 5 times
> 	hibme-drm 0000:83:00.0: [drm] *ERROR* dp link training failed, ret: -16
> 	hibmc-drm 0000:83:00.0: [drm] *ERROR* hibme dp mode set failed: -16
> 
> Fixes: 3c7623fb5bb6 ("drm/hisilicon/hibmc: Enable this hot plug detect of irq feature")
> Signed-off-by: Baihan Li <libaihan@...wei.com>
> Signed-off-by: Yongbang Shi <shiyongbang@...wei.com>
> Reviewed-by: Tao Tian <tiantao6@...ilicon.com>
> ---
> ChangeLog:
> v9 -> v10:
>   - delete 100ms delay in hibmc_dp_check_hpd_status().
>   - delete redundant checks in atomic_enable().
> v8 -> v9:
>   - refactor the hibmc_dp_check_hpd_status(), and add some checks
>     in dp_encoder_enable.
> v7 -> v8:
>   - fix build errors reported by kernel test robot <lkp@...el.com>
>     Closes: https://lore.kernel.org/oe-kbuild-all/202509241625.o4mNleVb-lkp@intel.com/
> v6 -> v7:
>   - add the check about branch devices, suggested by Dmitry Baryshkov.
> v5 -> v6:
>   - use HPD status in DP detect_ctx(), suggested by Dmitry Baryshkov.
> v4 -> v5:
>   - fix the commit message and DP detect_ctx(), suggested by Dmitry Baryshkov.
> ---
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h  |  4 ++
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c    | 19 +++++++
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h    |  6 +++
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h   |  3 ++
>  .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    | 52 +++++++++++++++++--
>  5 files changed, 80 insertions(+), 4 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>


-- 
With best wishes
Dmitry