Re: [Intel-gfx] [PATCH] drm/i915: Add bigjoiner force enable option to debugfs

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 09 Oct 2023, Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> 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.
>
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  | 71 +++++++++++++++++++
>  .../drm/i915/display/intel_display_types.h    |  2 +
>  drivers/gpu/drm/i915/display/intel_dp.c       |  6 +-
>  3 files changed, 78 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 f6d7c4d45fae..c806957cb902 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -1399,6 +1399,35 @@ out:	drm_modeset_unlock(&dev->mode_config.connection_mutex);
>  	return ret;
>  }
>  
> +static int i915_bigjoiner_enable_show(struct seq_file *m, void *data)
> +{
> +	struct drm_connector *connector = m->private;

struct intel_connector *connector, please. Yeah, this is copy-paste from
other files, but they should be changed too.

> +	struct drm_device *dev = connector->dev;

struct drm_i915_private *i915, please.

> +	struct drm_crtc *crtc;
> +	struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
> +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	int ret;
> +
> +	if (!encoder)
> +		return -ENODEV;
> +
> +	ret = drm_modeset_lock_single_interruptible(&dev->mode_config.connection_mutex);
> +	if (ret)
> +		return ret;

Why does show need locking but write doesn't?

> +
> +	crtc = connector->state->crtc;
> +	if (connector->status != connector_status_connected || !crtc) {
> +		ret = -ENODEV;
> +		goto out;
> +	}

I guess because of the above, but... do we need it? Or is this just
copy-pasted from some other debugfs files, which copy-pasted from other
debugfs files, which... ;)

> +
> +	seq_printf(m, "Bigjoiner enable: %d\n", intel_dp->force_bigjoiner_en);
> +
> +out:	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +	return ret;
> +}
> +
>  static ssize_t i915_dsc_output_format_write(struct file *file,
>  					    const char __user *ubuf,
>  					    size_t len, loff_t *offp)
> @@ -1420,12 +1449,39 @@ 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 drm_connector *connector =
> +		((struct seq_file *)file->private_data)->private;

I think this reads better with

	struct seq_file *m = file->private_data;
        struct intel_connector *connector = m->private;

> +	struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
> +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	int bigjoiner_en = 0;
> +	int ret;
> +
> +	ret = kstrtoint_from_user(ubuf, len, 0, &bigjoiner_en);
> +	if (ret < 0)
> +		return ret;

If it's a bool, why kstrtoint? Yeah, because copy-paste, but why keep
percolating the same mistakes?

> +
> +	intel_dp->force_bigjoiner_en = 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,
> @@ -1435,6 +1491,15 @@ static const struct file_operations i915_dsc_output_format_fops = {
>  	.write = i915_dsc_output_format_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
> +};
> +
>  /*
>   * Returns the Current CRTC's bpc.
>   * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/i915_current_bpc
> @@ -1514,6 +1579,12 @@ void intel_connector_debugfs_add(struct intel_connector *intel_connector)
>  				    connector, &i915_dsc_output_format_fops);
>  	}
>  
> +	if (DISPLAY_VER(dev_priv) >= 11 &&
> +	    connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
> +		debugfs_create_file("i915_bigjoiner_force_enable", 0644, root,
> +				    connector, &i915_bigjoiner_enable_fops);

All of these should just pass struct intel_connector.

> +	}
> +
>  	if (connector->connector_type == DRM_MODE_CONNECTOR_DSI ||
>  	    connector->connector_type == DRM_MODE_CONNECTOR_eDP ||
>  	    connector->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 8d8b2f8d37a9..ecec8a25838e 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1753,6 +1753,8 @@ struct intel_dp {
>  	bool is_mst;
>  	int active_mst_links;
>  
> +	bool force_bigjoiner_en;

No need to try to shorten this, just spell out 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 f0f43aeabd21..7e553cb7ecbb 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1153,7 +1153,11 @@ 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;
> +	if (intel_dp->force_bigjoiner_en)
> +		drm_dbg_kms(&i915->drm, "Forcing bigjoiner mode");

Missing \n.

> +
> +	return clock > i915->max_dotclk_freq || hdisplay > 5120 ||
> +	       intel_dp->force_bigjoiner_en;
>  }
>  
>  static enum drm_mode_status

-- 
Jani Nikula, Intel