linux-kernel - Re: [PATCH drm-dp 09/10] drm/hisilicon/hibmc: fix HPD no showing with VGA para of GRUB

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Message-ID: <5nansqkys4d3wlsefql6itgnpdoxhgjo7kkmovpm3gfbphxcs6@4anxx7hzoimh>
Date: Sun, 8 Jun 2025 15:47:23 +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 09/10] drm/hisilicon/hibmc: fix HPD no showing
 with VGA para of GRUB

On Fri, May 30, 2025 at 05:54:31PM +0800, Yongbang Shi wrote:
> From: Baihan Li <libaihan@...wei.com>
> 
> In early OS versions， there is a bug in hibmc-drm driver previously,

Which OS? What does that mean? Why do we need to workaround userspace
issues in the kernel?

> so some OS add a VGA parameter in GRUB(video=VGA-1:640x480-32@...e) to
> fix the bug, that will config a force VGA mode to drm driver. However, the
> HPD problem exists that mentioned in previous patch, so change VGA's status
> in force() to compatible with some older OS versions.
> 
> Fixes: f9698f802e50 ("drm/hisilicon/hibmc: Restructuring the header dp_reg.h")
> Signed-off-by: Baihan Li <libaihan@...wei.com>
> ---
>  drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> index 73dd3d5fc26c..d609ccda2f2a 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> @@ -61,6 +61,19 @@ static int hibmc_vdac_detect(struct drm_connector *connector, struct drm_modeset
>  	return connector_status_connected;
>  }
>  
> +static void hibmc_vdac_force(struct drm_connector *connector)
> +{
> +	struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
> +	struct hibmc_dp *dp = &priv->dp;
> +
> +	if (dp->hpd_status) {
> +		connector->status = connector_status_disconnected;
> +		return;
> +	}
> +
> +	connector->status = connector_status_connected;

You are again trying to tie VGA and DP status, so NAK.

> +}
> +
>  static void hibmc_connector_destroy(struct drm_connector *connector)
>  {
>  	struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
> @@ -81,6 +94,7 @@ static const struct drm_connector_funcs hibmc_connector_funcs = {
>  	.reset = drm_atomic_helper_connector_reset,
>  	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
>  	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +	.force = hibmc_vdac_force,
>  };
>  
>  static void hibmc_encoder_mode_set(struct drm_encoder *encoder,
> -- 
> 2.33.0
> 

-- 
With best wishes
Dmitry