Re: [PATCH 1/3] drm/i915: Add bigjoiner force enable option to debugfs

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

On Mon, Jan 08, 2024 at 02:07:23PM +0200, Stanislav Lisovskiy wrote:
> For validation purposes, it might be useful to be able to
> force Bigjoiner mode, even if current dotclock/resolution
> do not require that.
> Lets add such to option to debugfs.
> 
> v2: - Apparently intel_dp_need_bigjoiner can't be used, when
>       debugfs entry is created so lets just check manually
>       the DISPLAY_VER.
> 
> v3: - Switch to intel_connector from drm_connector(Jani Nikula)
>     - Remove redundant modeset lock(Jani Nikula)
>     - Use kstrtobool_from_user for boolean value(Jani Nikula)
> 
> v4: - Apply the changes to proper function(Jani Nikula)
> 
> v5: - Removed unnecessary check from i915_bigjoiner_enable_show
>       (Ville Syrjälä)
>     - Added eDP connector check to intel_connector_debugfs_add
>       (Ville Syrjälä)
>     - Removed debug message in order to prevent dmesg flooding
>       (Ville Syrjälä)
> 
> v6: - Assume now always that m->private is intel_connector
>     - Fixed other similar conflicts
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  | 59 +++++++++++++++++++
>  .../drm/i915/display/intel_display_types.h    |  2 +
>  drivers/gpu/drm/i915/display/intel_dp.c       |  3 +-
>  3 files changed, 63 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index d951edb366871..353e71b4e1db2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -1413,6 +1413,22 @@ out:	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
>  	return ret;
>  }
>  
> +static int i915_bigjoiner_enable_show(struct seq_file *m, void *data)
> +{
> +	struct intel_connector *connector = m->private;
> +	struct intel_encoder *encoder = intel_attached_encoder(connector);
> +	struct intel_dp *intel_dp;
> +
> +	if (!encoder)
> +		return -ENODEV;
> +
> +	intel_dp = enc_to_intel_dp(encoder);
> +
> +	seq_printf(m, "Bigjoiner enable: %d\n", intel_dp->force_bigjoiner_enable);

So it's a per-connector debugfs knob but we track it in the
SST DP encoder? That's rather odd, and not going to work for MST.

> +
> +	return 0;
> +}
> +
>  static ssize_t i915_dsc_output_format_write(struct file *file,
>  					    const char __user *ubuf,
>  					    size_t len, loff_t *offp)
> @@ -1434,12 +1450,39 @@ static ssize_t i915_dsc_output_format_write(struct file *file,
>  	return len;
>  }
>  
> +static ssize_t i915_bigjoiner_enable_fops_write(struct file *file,
> +						const char __user *ubuf,
> +						size_t len, loff_t *offp)
> +{
> +	struct seq_file *m = file->private_data;
> +	struct intel_connector *connector = m->private;
> +	struct intel_encoder *encoder = intel_attached_encoder(connector);
> +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	bool bigjoiner_en = 0;
> +	int ret;
> +
> +	ret = kstrtobool_from_user(ubuf, len, &bigjoiner_en);
> +	if (ret < 0)
> +		return ret;
> +
> +	intel_dp->force_bigjoiner_enable = bigjoiner_en;
> +	*offp += len;
> +
> +	return len;
> +}
> +
>  static int i915_dsc_output_format_open(struct inode *inode,
>  				       struct file *file)
>  {
>  	return single_open(file, i915_dsc_output_format_show, inode->i_private);
>  }
>  
> +static int i915_bigjoiner_enable_open(struct inode *inode,
> +				      struct file *file)
> +{
> +	return single_open(file, i915_bigjoiner_enable_show, inode->i_private);
> +}
> +
>  static const struct file_operations i915_dsc_output_format_fops = {
>  	.owner = THIS_MODULE,
>  	.open = i915_dsc_output_format_open,
> @@ -1527,6 +1570,15 @@ static const struct file_operations i915_dsc_fractional_bpp_fops = {
>  	.write = i915_dsc_fractional_bpp_write
>  };
>  
> +static const struct file_operations i915_bigjoiner_enable_fops = {
> +	.owner = THIS_MODULE,
> +	.open = i915_bigjoiner_enable_open,
> +	.read = seq_read,
> +	.llseek = seq_lseek,
> +	.release = single_release,
> +	.write = i915_bigjoiner_enable_fops_write
> +};

Why are we implementing this long-hand for a simple boolean flag?

> +
>  /*
>   * Returns the Current CRTC's bpc.
>   * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/i915_current_bpc
> @@ -1608,6 +1660,13 @@ void intel_connector_debugfs_add(struct intel_connector *connector)
>  				    connector, &i915_dsc_fractional_bpp_fops);
>  	}
>  
> +	if (DISPLAY_VER(i915) >= 11 &&
> +	    (connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
> +	     connector_type == DRM_MODE_CONNECTOR_eDP)) {
> +		debugfs_create_file("i915_bigjoiner_force_enable", 0644, root,
> +				    &connector->base, &i915_bigjoiner_enable_fops);
> +	}
> +
>  	if (connector_type == DRM_MODE_CONNECTOR_DSI ||
>  	    connector_type == DRM_MODE_CONNECTOR_eDP ||
>  	    connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index b9b9d9f2bc0ba..e4c5a44dd02f5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1768,6 +1768,8 @@ struct intel_dp {
>  	bool is_mst;
>  	int active_mst_links;
>  
> +	bool force_bigjoiner_enable;
> +
>  	/* connector directly attached - won't be use for modeset in mst world */
>  	struct intel_connector *attached_connector;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 9ff0cbd9c0df5..525ab926582d5 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1208,7 +1208,8 @@ bool intel_dp_need_bigjoiner(struct intel_dp *intel_dp,
>  	if (!intel_dp_can_bigjoiner(intel_dp))
>  		return false;
>  
> -	return clock > i915->max_dotclk_freq || hdisplay > 5120;
> +	return clock > i915->max_dotclk_freq || hdisplay > 5120 ||
> +	       intel_dp->force_bigjoiner_enable;
>  }
>  
>  static enum drm_mode_status
> -- 
> 2.37.3

-- 
Ville Syrjälä
Intel