drm/i915/dram: add return value and handling to intel_dram_detect()

We'll want to start returning errors from intel_dram_detect(). As the
first step, add the return value and error handling, even if we still
only return 0.

Do no functional changes, but leave a comment about whether we should
bail out on dram detection failures.

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Link: https://lore.kernel.org/r/be2c31c459fb95d8161b719d499403eea5ec17b7.1748337870.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Author: jnikula

drivers/gpu/drm/i915/i915_driver.c

@@ -568,7 +568,9 @@ static int i915_driver_hw_probe(struct drm_i915_private *dev_priv)
 	 * Fill the dram structure to get the system dram info. This will be
 	 * used for memory latency calculation.
 	 */
-	intel_dram_detect(dev_priv);
+	ret = intel_dram_detect(dev_priv);
+	if (ret)
+		goto err_opregion;
 
 	intel_bw_init_hw(display);
 

drivers/gpu/drm/i915/soc/intel_dram.c

@@ -704,7 +704,7 @@ static int xelpdp_get_dram_info(struct drm_i915_private *i915, struct dram_info
 	return 0;
 }
 
-void intel_dram_detect(struct drm_i915_private *i915)
+int intel_dram_detect(struct drm_i915_private *i915)
 {
 	struct dram_info *dram_info = &i915->dram_info;
 	int ret;
@@ -713,7 +713,7 @@ void intel_dram_detect(struct drm_i915_private *i915)
 	detect_mem_freq(i915);
 
 	if (GRAPHICS_VER(i915) < 9 || IS_DG2(i915) || !HAS_DISPLAY(i915))
-		return;
+		return 0;
 
 	/*
 	 * Assume level 0 watermark latency adjustment is needed until proven
@@ -735,15 +735,18 @@ void intel_dram_detect(struct drm_i915_private *i915)
 	drm_dbg_kms(&i915->drm, "DRAM type: %s\n",
 		    intel_dram_type_str(dram_info->type));
 
+	/* TODO: Do we want to abort probe on dram detection failures? */
 	if (ret)
-		return;
+		return 0;
 
 	drm_dbg_kms(&i915->drm, "Num qgv points %u\n", dram_info->num_qgv_points);
 
 	drm_dbg_kms(&i915->drm, "DRAM channels: %u\n", dram_info->num_channels);
 
 	drm_dbg_kms(&i915->drm, "Watermark level 0 adjustment needed: %s\n",
 		    str_yes_no(dram_info->wm_lv_0_adjust_needed));
+
+	return 0;
 }
 
 const struct dram_info *intel_dram_info(struct drm_device *drm)

drivers/gpu/drm/i915/soc/intel_dram.h

@@ -11,7 +11,7 @@ struct drm_device;
 struct dram_info;
 
 void intel_dram_edram_detect(struct drm_i915_private *i915);
-void intel_dram_detect(struct drm_i915_private *i915);
+int intel_dram_detect(struct drm_i915_private *i915);
 unsigned int i9xx_fsb_freq(struct drm_i915_private *i915);
 const struct dram_info *intel_dram_info(struct drm_device *drm);
 

drivers/gpu/drm/xe/display/xe_display.c

@@ -122,7 +122,9 @@ int xe_display_init_early(struct xe_device *xe)
 	 * Fill the dram structure to get the system dram info. This will be
 	 * used for memory latency calculation.
 	 */
-	intel_dram_detect(xe);
+	err = intel_dram_detect(xe);
+	if (err)
+		goto err_opregion;
 
 	intel_bw_init_hw(display);