linux-kernel - Re: [PATCH drm-dp 05/10] drm/hisilicon/hibmc: fix rare monitors cannot display problem

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Message-ID: <j23q7vjp2s2gfautba7hcbvd5vrrycr5akl3m24eu4nlvy65s7@5uytzwucogxw>
Date: Sun, 8 Jun 2025 15:36:31 +0300
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, lidongming5@...wei.com, libaihan@...wei.com,
        shenjian15@...wei.com, shaojijie@...wei.com,
        jani.nikula@...ux.intel.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-dp 05/10] drm/hisilicon/hibmc: fix rare monitors
 cannot display problem

On Fri, May 30, 2025 at 05:54:27PM +0800, Yongbang Shi wrote:
> From: Baihan Li <libaihan@...wei.com>
> 
> DP Link training successful at 8.1Gbps with some monitors' max link rate
> are 2.7Gbps. So change the default 8.1Gbps link rate to the rate that reads
> from devices' capabilities.

I've hard time understanding this message.

> 
> Fixes: f9698f802e50 ("drm/hisilicon/hibmc: Restructuring the header dp_reg.h")

No, the tag is incorrect. Mentioned commit is not related.

> Signed-off-by: Baihan Li <libaihan@...wei.com>
> ---
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h  |  4 ++-
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c    |  6 +---
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c  | 33 +++++++++++++------
>  .../gpu/drm/hisilicon/hibmc/dp/dp_serdes.c    | 12 -------
>  4 files changed, 27 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> index 676059d4c1e6..8191233aa965 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> @@ -57,15 +57,3 @@ int hibmc_dp_serdes_rate_switch(u8 rate, struct hibmc_dp_dev *dp)
>  
>  	return 0;
>  }
> -
> -int hibmc_dp_serdes_init(struct hibmc_dp_dev *dp)
> -{
> -	dp->serdes_base = dp->base + HIBMC_DP_HOST_OFFSET;
> -
> -	writel(FIELD_PREP(HIBMC_DP_PMA_TXDEEMPH, DP_SERDES_VOL0_PRE0),
> -	       dp->serdes_base + HIBMC_DP_PMA_LANE0_OFFSET);
> -	writel(FIELD_PREP(HIBMC_DP_PMA_TXDEEMPH, DP_SERDES_VOL0_PRE0),
> -	       dp->serdes_base + HIBMC_DP_PMA_LANE1_OFFSET);

Where did these two writes go?

> -
> -	return hibmc_dp_serdes_rate_switch(DP_SERDES_BW_8_1, dp);
> -}
> -- 
> 2.33.0
> 

-- 
With best wishes
Dmitry