drm/i915/dsc: Add debugfs entry to validate DSC fractional bpp

DSC_Sink_BPP_Precision entry is added to i915_dsc_fec_support_show
to depict sink's precision.
Also, new debugfs entry is created to enforce fractional bpp.
If Force_DSC_Fractional_BPP_en is set then while iterating over
output bpp with fractional step size we will continue if output_bpp is
computed as integer. With this approach, we will be able to validate
DSC with fractional bpp.

v2:
Add drm_modeset_unlock to new line(Suraj)
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Link: https://patchwork.freedesktop.org/patch/msgid/20231110101020.4067342-8-ankit.k.nautiyal@intel.com

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

@@ -1257,6 +1257,8 @@ static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
 								      DP_DSC_YCbCr420_Native)),
 			   str_yes_no(drm_dp_dsc_sink_supports_format(connector->dp.dsc_dpcd,
 								      DP_DSC_YCbCr444)));
+		seq_printf(m, "DSC_Sink_BPP_Precision: %d\n",
+			   drm_dp_dsc_sink_bpp_incr(connector->dp.dsc_dpcd));
 		seq_printf(m, "Force_DSC_Enable: %s\n",
 			   str_yes_no(intel_dp->force_dsc_en));
 		if (!intel_dp_is_edp(intel_dp))
@@ -1449,6 +1451,85 @@ static const struct file_operations i915_dsc_output_format_fops = {
 	.write = i915_dsc_output_format_write
 };
 
+static int i915_dsc_fractional_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_dp *intel_dp;
+	struct intel_connector *intel_connector = to_intel_connector(connector);
+	struct intel_encoder *encoder = intel_attached_encoder(intel_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;
+	}
+
+	intel_dp = intel_attached_dp(intel_connector);
+	seq_printf(m, "Force_DSC_Fractional_BPP_Enable: %s\n",
+		   str_yes_no(intel_dp->force_dsc_fractional_bpp_en));
+
+out:
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+	return ret;
+}
+
+static ssize_t i915_dsc_fractional_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 drm_i915_private *i915 = to_i915(encoder->base.dev);
+	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+	bool dsc_fractional_bpp_enable = false;
+	int ret;
+
+	if (len == 0)
+		return 0;
+
+	drm_dbg(&i915->drm,
+		"Copied %zu bytes from user to force fractional bpp for DSC\n", len);
+
+	ret = kstrtobool_from_user(ubuf, len, &dsc_fractional_bpp_enable);
+	if (ret < 0)
+		return ret;
+
+	drm_dbg(&i915->drm, "Got %s for DSC Fractional BPP Enable\n",
+		(dsc_fractional_bpp_enable) ? "true" : "false");
+	intel_dp->force_dsc_fractional_bpp_en = dsc_fractional_bpp_enable;
+
+	*offp += len;
+
+	return len;
+}
+
+static int i915_dsc_fractional_bpp_open(struct inode *inode,
+					struct file *file)
+{
+	return single_open(file, i915_dsc_fractional_bpp_show, inode->i_private);
+}
+
+static const struct file_operations i915_dsc_fractional_bpp_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_dsc_fractional_bpp_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = i915_dsc_fractional_bpp_write
+};
+
 /*
  * Returns the Current CRTC's bpc.
  * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/i915_current_bpc
@@ -1526,6 +1607,9 @@ void intel_connector_debugfs_add(struct intel_connector *intel_connector)
 
 		debugfs_create_file("i915_dsc_output_format", 0644, root,
 				    connector, &i915_dsc_output_format_fops);
+
+		debugfs_create_file("i915_dsc_fractional_bpp", 0644, root,
+				    connector, &i915_dsc_fractional_bpp_fops);
 	}
 
 	if (connector->connector_type == DRM_MODE_CONNECTOR_DSI ||

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

@@ -1815,6 +1815,7 @@ struct intel_dp {
 	/* Display stream compression testing */
 	bool force_dsc_en;
 	int force_dsc_output_format;
+	bool force_dsc_fractional_bpp_en;
 	int force_dsc_bpc;
 
 	bool hobl_failed;