drm/i915/display/dsc: Add Per connector debugfs node for DSC BPP enable

This patch creates a per connector debugfs node to expose
the Compressed BPP. The same node can be used from userspace
to force DSC to a certain BPP(all accepted values).

This is useful to verify all supported/requested
compression bpp's through IGT

v2: Remove unnecessary logic (Jani)
v3: Drop pipe bpp in debugfs node (Vandita)
v4: Minor cleanups (Vandita)
v5: Fix NULL pointer dereference
v6: Fix dim tool checkpatch errors
    Release the lock before return (Vandita)
v7: Rename to file to dsc_bpp, remove unwanted
    dsc bpp range check from v6, permissions (Jani)

Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Navare Manasi D <manasi.d.navare@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Patnana Venkata Sai <venkata.sai.patnana@intel.com>
Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210720064907.9771-3-vandita.kulkarni@intel.com

drivers/gpu/drm/i915/display/intel_display_debugfs.c

@@ -2395,6 +2395,73 @@ static const struct file_operations i915_dsc_fec_support_fops = {
 	.write = i915_dsc_fec_support_write
 };
 
+static int i915_dsc_bpp_show(struct seq_file *m, void *data)
+{
+	struct drm_connector *connector = m->private;
+	struct drm_device *dev = connector->dev;
+	struct drm_crtc *crtc;
+	struct intel_crtc_state *crtc_state;
+	struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
+	int ret;
+
+	if (!encoder)
+		return -ENODEV;
+
+	ret = drm_modeset_lock_single_interruptible(&dev->mode_config.connection_mutex);
+	if (ret)
+		return ret;
+
+	crtc = connector->state->crtc;
+	if (connector->status != connector_status_connected || !crtc) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	crtc_state = to_intel_crtc_state(crtc->state);
+	seq_printf(m, "Compressed_BPP: %d\n", crtc_state->dsc.compressed_bpp);
+
+out:	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+	return ret;
+}
+
+static ssize_t i915_dsc_bpp_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;
+	struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
+	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+	int dsc_bpp = 0;
+	int ret;
+
+	ret = kstrtoint_from_user(ubuf, len, 0, &dsc_bpp);
+	if (ret < 0)
+		return ret;
+
+	intel_dp->force_dsc_bpp = dsc_bpp;
+	*offp += len;
+
+	return len;
+}
+
+static int i915_dsc_bpp_open(struct inode *inode,
+			     struct file *file)
+{
+	return single_open(file, i915_dsc_bpp_show,
+			   inode->i_private);
+}
+
+static const struct file_operations i915_dsc_bpp_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_dsc_bpp_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = i915_dsc_bpp_write
+};
+
 /**
  * intel_connector_debugfs_add - add i915 specific connector debugfs files
  * @connector: pointer to a registered drm_connector
@@ -2433,10 +2500,17 @@ int intel_connector_debugfs_add(struct drm_connector *connector)
 				    connector, &i915_hdcp_sink_capability_fops);
 	}
 
-	if ((DISPLAY_VER(dev_priv) >= 11 || IS_CANNONLAKE(dev_priv)) && ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort && !to_intel_connector(connector)->mst_port) || connector->connector_type == DRM_MODE_CONNECTOR_eDP))
+	if ((DISPLAY_VER(dev_priv) >= 11 || IS_CANNONLAKE(dev_priv)) &&
+	    ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort &&
+	    !to_intel_connector(connector)->mst_port) ||
+	    connector->connector_type == DRM_MODE_CONNECTOR_eDP)) {
 		debugfs_create_file("i915_dsc_fec_support", 0644, root,
 				    connector, &i915_dsc_fec_support_fops);
 
+		debugfs_create_file("i915_dsc_bpp", 0644, root,
+				    connector, &i915_dsc_bpp_fops);
+	}
+
 	/* Legacy panels doesn't lpsp on any platform */
 	if ((DISPLAY_VER(dev_priv) >= 9 || IS_HASWELL(dev_priv) ||
 	     IS_BROADWELL(dev_priv)) &&

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1612,6 +1612,7 @@ struct intel_dp {
 
 	/* Display stream compression testing */
 	bool force_dsc_en;
+	int force_dsc_bpp;
 
 	bool hobl_failed;
 	bool hobl_active;