Re: [Intel-gfx] [PATCH] drm/i915: Fix the i915_dsc_fec_support debugfs file for DP MST connectors

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Jun 08, 2020 at 09:10:23PM +0300, Imre Deak wrote:
> DSC is not supported on DP MST streams so just return -EINVAL when
> reading/writing the i915_dsc_fec_support debugfs file for such
> connectors.
> 
> This also fixes an OOPS, caused by the encoder->digport cast, which is
> not valid for MST encoders.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  | 36 +++++++++++++++----
>  1 file changed, 29 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index 2b640d8ab9d2..ebca8e488d03 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -2094,6 +2094,8 @@ static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
>  	drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);
>  
>  	do {
> +		struct intel_encoder *encoder;
> +
>  		try_again = false;
>  		ret = drm_modeset_lock(&dev->mode_config.connection_mutex,
>  				       &ctx);
> @@ -2120,8 +2122,17 @@ static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
>  		} else if (ret) {
>  			break;
>  		}
> -		intel_dp = intel_attached_dp(to_intel_connector(connector));
> +
> +		encoder = intel_attached_encoder(to_intel_connector(connector));
> +		/* TODO: Add DSC support for MST streams */
> +		if (encoder->type == INTEL_OUTPUT_DP_MST) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		intel_dp = &enc_to_dig_port(encoder)->dp;
>  		crtc_state = to_intel_crtc_state(crtc->state);
> +
>  		seq_printf(m, "DSC_Enabled: %s\n",
>  			   yesno(crtc_state->dsc.compression_enable));
>  		seq_printf(m, "DSC_Sink_Support: %s\n",
> @@ -2147,9 +2158,8 @@ static ssize_t i915_dsc_fec_support_write(struct file *file,
>  	int ret;
>  	struct drm_connector *connector =
>  		((struct seq_file *)file->private_data)->private;
> -	struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
> -	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
> -	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	struct drm_i915_private *i915 = to_i915(connector->dev);
> +	struct intel_encoder *encoder;
>  
>  	if (len == 0)
>  		return 0;
> @@ -2163,10 +2173,22 @@ static ssize_t i915_dsc_fec_support_write(struct file *file,
>  
>  	drm_dbg(&i915->drm, "Got %s for DSC Enable\n",
>  		(dsc_enable) ? "true" : "false");
> -	intel_dp->force_dsc_en = dsc_enable;
>  
> -	*offp += len;
> -	return len;
> +	drm_modeset_lock(&i915->drm.mode_config.connection_mutex, NULL);
> +
> +	encoder = intel_attached_encoder(to_intel_connector(connector));
> +	/* TODO: Add DSC support for MST streams */
> +	if (encoder->type == INTEL_OUTPUT_DP_MST) {

The attached encoder can be NULL for MST.

Can't we just not add this debugfs file for MST connectors?

> +		ret = -EINVAL;
> +	} else {
> +		enc_to_intel_dp(encoder)->force_dsc_en = dsc_enable;
> +		*offp += len;
> +		ret = len;
> +	}
> +
> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +	return ret;
>  }
>  
>  static int i915_dsc_fec_support_open(struct inode *inode,
> -- 
> 2.23.1
> 
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-- 
Ville Syrjälä
Intel
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