drm/xe/pm: Init pcode and restore vram on power lost

Don't init pcode and restore VRAM objects in vain.
We can rely on primary GT GUC_STATUS to detect whether
card has really lost power even when d3cold is allowed by xe.
Adding d3cold.lost_power flag to avoid pcode init and vram
restoration.
Also cleaning up the TODO code comment.

v2:
- %s/xe_guc_has_lost_power()/xe_guc_in_reset().
- Used existing gt instead of new variable. [Rodrigo]
- Added kernel-doc function comment. [Rodrigo]
- xe_guc_in_reset() return true if failed to get fw.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230718080703.239343-6-anshuman.gupta@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_device_types.h

@@ -335,6 +335,9 @@ struct xe_device {
 		/** @allowed: Indicates if d3cold is a valid device state */
 		bool allowed;
 
+		/** @power_lost: Indicates if card has really lost power. */
+		bool power_lost;
+
 		/**
 		 * @vram_threshold:
 		 *

drivers/gpu/drm/xe/xe_guc.c

@@ -844,3 +844,30 @@ void xe_guc_print_info(struct xe_guc *guc, struct drm_printer *p)
 	xe_guc_ct_print(&guc->ct, p, false);
 	xe_guc_submit_print(guc, p);
 }
+
+/**
+ * xe_guc_in_reset() - Detect if GuC MIA is in reset.
+ * @guc: The GuC object
+ *
+ * This function detects runtime resume from d3cold by leveraging
+ * GUC_STATUS, GUC doesn't get reset during d3hot,
+ * it strictly to be called from RPM resume handler.
+ *
+ * Return: true if failed to get forcewake or GuC MIA is in Reset,
+ * otherwise false.
+ */
+bool xe_guc_in_reset(struct xe_guc *guc)
+{
+	struct xe_gt *gt = guc_to_gt(guc);
+	u32 status;
+	int err;
+
+	err = xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
+	if (err)
+		return true;
+
+	status = xe_mmio_read32(gt, GUC_STATUS);
+	xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
+
+	return  status & GS_MIA_IN_RESET;
+}

drivers/gpu/drm/xe/xe_guc.h

@@ -35,6 +35,7 @@ void xe_guc_reset_wait(struct xe_guc *guc);
 void xe_guc_stop_prepare(struct xe_guc *guc);
 int xe_guc_stop(struct xe_guc *guc);
 int xe_guc_start(struct xe_guc *guc);
+bool xe_guc_in_reset(struct xe_guc *guc);
 
 static inline u16 xe_engine_class_to_guc_class(enum xe_engine_class class)
 {

drivers/gpu/drm/xe/xe_pci.c

@@ -818,8 +818,6 @@ static int xe_pci_runtime_idle(struct device *dev)
 		 * but maybe include some other conditions. So, before
 		 * we can re-enable the D3cold, we need to:
 		 * 1. rewrite the VRAM save / restore to avoid buffer object locks
-		 * 2. at resume, detect if we really lost power and avoid memory
-		 *    restoration if we were only up to d3cold
 		 */
 		xe->d3cold.allowed = false;
 	}

drivers/gpu/drm/xe/xe_pm.c

@@ -16,6 +16,7 @@
 #include "xe_device_sysfs.h"
 #include "xe_ggtt.h"
 #include "xe_gt.h"
+#include "xe_guc.h"
 #include "xe_irq.h"
 #include "xe_pcode.h"
 
@@ -186,7 +187,15 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 	u8 id;
 	int err;
 
-	if (xe->d3cold.allowed) {
+	/*
+	 * It can be possible that xe has allowed d3cold but other pcie devices
+	 * in gfx card soc would have blocked d3cold, therefore card has not
+	 * really lost power. Detecting primary Gt power is sufficient.
+	 */
+	gt = xe_device_get_gt(xe, 0);
+	xe->d3cold.power_lost = xe_guc_in_reset(&gt->uc.guc);
+
+	if (xe->d3cold.allowed && xe->d3cold.power_lost) {
 		for_each_gt(gt, xe, id) {
 			err = xe_pcode_init(gt);
 			if (err)
@@ -207,7 +216,7 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 	for_each_gt(gt, xe, id)
 		xe_gt_resume(gt);
 
-	if (xe->d3cold.allowed) {
+	if (xe->d3cold.allowed && xe->d3cold.power_lost) {
 		err = xe_bo_restore_user(xe);
 		if (err)
 			return err;