1 files changed, 430 insertions, 70 deletions

diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
index b429c2876a76..89fd2c043136 100644
--- a/drivers/gpu/drm/xe/xe_pm.c
+++ b/drivers/gpu/drm/xe/xe_pm.c
@@ -5,43 +5,108 @@
 
 #include "xe_pm.h"
 
+#include <linux/fault-inject.h>
 #include <linux/pm_runtime.h>
+#include <linux/suspend.h>
 
 #include <drm/drm_managed.h>
 #include <drm/ttm/ttm_placement.h>
 
+#include "display/xe_display.h"
 #include "xe_bo.h"
 #include "xe_bo_evict.h"
 #include "xe_device.h"
 #include "xe_device_sysfs.h"
-#include "xe_display.h"
 #include "xe_ggtt.h"
 #include "xe_gt.h"
 #include "xe_guc.h"
 #include "xe_irq.h"
 #include "xe_pcode.h"
+#include "xe_trace.h"
 #include "xe_wa.h"
 
 /**
  * DOC: Xe Power Management
  *
- * Xe PM shall be guided by the simplicity.
- * Use the simplest hook options whenever possible.
- * Let's not reinvent the runtime_pm references and hooks.
- * Shall have a clear separation of display and gt underneath this component.
+ * Xe PM implements the main routines for both system level suspend states and
+ * for the opportunistic runtime suspend states.
  *
- * What's next:
+ * System Level Suspend (S-States) - In general this is OS initiated suspend
+ * driven by ACPI for achieving S0ix (a.k.a. S2idle, freeze), S3 (suspend to ram),
+ * S4 (disk). The main functions here are `xe_pm_suspend` and `xe_pm_resume`. They
+ * are the main point for the suspend to and resume from these states.
  *
- * For now s2idle and s3 are only working in integrated devices. The next step
- * is to iterate through all VRAM's BO backing them up into the system memory
- * before allowing the system suspend.
+ * PCI Device Suspend (D-States) - This is the opportunistic PCIe device low power
+ * state D3, controlled by the PCI subsystem and ACPI with the help from the
+ * runtime_pm infrastructure.
+ * PCI D3 is special and can mean D3hot, where Vcc power is on for keeping memory
+ * alive and quicker low latency resume or D3Cold where Vcc power is off for
+ * better power savings.
+ * The Vcc control of PCI hierarchy can only be controlled at the PCI root port
+ * level, while the device driver can be behind multiple bridges/switches and
+ * paired with other devices. For this reason, the PCI subsystem cannot perform
+ * the transition towards D3Cold. The lowest runtime PM possible from the PCI
+ * subsystem is D3hot. Then, if all these paired devices in the same root port
+ * are in D3hot, ACPI will assist here and run its own methods (_PR3 and _OFF)
+ * to perform the transition from D3hot to D3cold. Xe may disallow this
+ * transition by calling pci_d3cold_disable(root_pdev) before going to runtime
+ * suspend. It will be based on runtime conditions such as VRAM usage for a
+ * quick and low latency resume for instance.
  *
- * Also runtime_pm needs to be here from the beginning.
+ * Runtime PM - This infrastructure provided by the Linux kernel allows the
+ * device drivers to indicate when the can be runtime suspended, so the device
+ * could be put at D3 (if supported), or allow deeper package sleep states
+ * (PC-states), and/or other low level power states. Xe PM component provides
+ * `xe_pm_runtime_suspend` and `xe_pm_runtime_resume` functions that PCI
+ * subsystem will call before transition to/from runtime suspend.
  *
- * RC6/RPS are also critical PM features. Let's start with GuCRC and GuC SLPC
- * and no wait boost. Frequency optimizations should come on a next stage.
+ * Also, Xe PM provides get and put functions that Xe driver will use to
+ * indicate activity. In order to avoid locking complications with the memory
+ * management, whenever possible, these get and put functions needs to be called
+ * from the higher/outer levels.
+ * The main cases that need to be protected from the outer levels are: IOCTL,
+ * sysfs, debugfs, dma-buf sharing, GPU execution.
+ *
+ * This component is not responsible for GT idleness (RC6) nor GT frequency
+ * management (RPS).
  */
 
+#ifdef CONFIG_LOCKDEP
+static struct lockdep_map xe_pm_runtime_d3cold_map = {
+	.name = "xe_rpm_d3cold_map"
+};
+
+static struct lockdep_map xe_pm_runtime_nod3cold_map = {
+	.name = "xe_rpm_nod3cold_map"
+};
+#endif
+
+/**
+ * xe_rpm_reclaim_safe() - Whether runtime resume can be done from reclaim context
+ * @xe: The xe device.
+ *
+ * Return: true if it is safe to runtime resume from reclaim context.
+ * false otherwise.
+ */
+bool xe_rpm_reclaim_safe(const struct xe_device *xe)
+{
+	return !xe->d3cold.capable && !xe->info.has_sriov;
+}
+
+static void xe_rpm_lockmap_acquire(const struct xe_device *xe)
+{
+	lock_map_acquire(xe_rpm_reclaim_safe(xe) ?
+			 &xe_pm_runtime_nod3cold_map :
+			 &xe_pm_runtime_d3cold_map);
+}
+
+static void xe_rpm_lockmap_release(const struct xe_device *xe)
+{
+	lock_map_release(xe_rpm_reclaim_safe(xe) ?
+			 &xe_pm_runtime_nod3cold_map :
+			 &xe_pm_runtime_d3cold_map);
+}
+
 /**
  * xe_pm_suspend - Helper for System suspend, i.e. S0->S3 / S0->S2idle
  * @xe: xe device instance
@@ -54,21 +119,24 @@ int xe_pm_suspend(struct xe_device *xe)
 	u8 id;
 	int err;
 
+	drm_dbg(&xe->drm, "Suspending device\n");
+	trace_xe_pm_suspend(xe, __builtin_return_address(0));
+
 	for_each_gt(gt, xe, id)
 		xe_gt_suspend_prepare(gt);
 
+	xe_display_pm_suspend(xe);
+
 	/* FIXME: Super racey... */
 	err = xe_bo_evict_all(xe);
 	if (err)
-		return err;
-
-	xe_display_pm_suspend(xe);
+		goto err;
 
 	for_each_gt(gt, xe, id) {
 		err = xe_gt_suspend(gt);
 		if (err) {
 			xe_display_pm_resume(xe);
-			return err;
+			goto err;
 		}
 	}
 
@@ -76,7 +144,11 @@ int xe_pm_suspend(struct xe_device *xe)
 
 	xe_display_pm_suspend_late(xe);
 
+	drm_dbg(&xe->drm, "Device suspended\n");
 	return 0;
+err:
+	drm_dbg(&xe->drm, "Device suspend failed %d\n", err);
+	return err;
 }
 
 /**
@@ -92,14 +164,15 @@ int xe_pm_resume(struct xe_device *xe)
 	u8 id;
 	int err;
 
+	drm_dbg(&xe->drm, "Resuming device\n");
+	trace_xe_pm_resume(xe, __builtin_return_address(0));
+
 	for_each_tile(tile, xe, id)
 		xe_wa_apply_tile_workarounds(tile);
 
-	for_each_gt(gt, xe, id) {
-		err = xe_pcode_init(gt);
-		if (err)
-			return err;
-	}
+	err = xe_pcode_ready(xe, true);
+	if (err)
+		return err;
 
 	xe_display_pm_resume_early(xe);
 
@@ -109,33 +182,46 @@ int xe_pm_resume(struct xe_device *xe)
 	 */
 	err = xe_bo_restore_kernel(xe);
 	if (err)
-		return err;
+		goto err;
 
 	xe_irq_resume(xe);
 
-	xe_display_pm_resume(xe);
-
 	for_each_gt(gt, xe, id)
 		xe_gt_resume(gt);
 
+	xe_display_pm_resume(xe);
+
 	err = xe_bo_restore_user(xe);
 	if (err)
-		return err;
+		goto err;
 
+	drm_dbg(&xe->drm, "Device resumed\n");
 	return 0;
+err:
+	drm_dbg(&xe->drm, "Device resume failed %d\n", err);
+	return err;
 }
 
-static bool xe_pm_pci_d3cold_capable(struct pci_dev *pdev)
+static bool xe_pm_pci_d3cold_capable(struct xe_device *xe)
 {
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
 	struct pci_dev *root_pdev;
 
 	root_pdev = pcie_find_root_port(pdev);
 	if (!root_pdev)
 		return false;
 
-	/* D3Cold requires PME capability and _PR3 power resource */
-	if (!pci_pme_capable(root_pdev, PCI_D3cold) || !pci_pr3_present(root_pdev))
+	/* D3Cold requires PME capability */
+	if (!pci_pme_capable(root_pdev, PCI_D3cold)) {
+		drm_dbg(&xe->drm, "d3cold: PME# not supported\n");
+		return false;
+	}
+
+	/* D3Cold requires _PR3 power resource */
+	if (!pci_pr3_present(root_pdev)) {
+		drm_dbg(&xe->drm, "d3cold: ACPI _PR3 not present\n");
 		return false;
+	}
 
 	return true;
 }
@@ -163,26 +249,72 @@ static void xe_pm_runtime_init(struct xe_device *xe)
 	pm_runtime_put(dev);
 }
 
-void xe_pm_init(struct xe_device *xe)
+int xe_pm_init_early(struct xe_device *xe)
 {
-	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+	int err;
+
+	INIT_LIST_HEAD(&xe->mem_access.vram_userfault.list);
+
+	err = drmm_mutex_init(&xe->drm, &xe->mem_access.vram_userfault.lock);
+	if (err)
+		return err;
+
+	err = drmm_mutex_init(&xe->drm, &xe->d3cold.lock);
+	if (err)
+		return err;
+
+	return 0;
+}
+ALLOW_ERROR_INJECTION(xe_pm_init_early, ERRNO); /* See xe_pci_probe() */
+
+static u32 vram_threshold_value(struct xe_device *xe)
+{
+	/* FIXME: D3Cold temporarily disabled by default on BMG */
+	if (xe->info.platform == XE_BATTLEMAGE)
+		return 0;
+
+	return DEFAULT_VRAM_THRESHOLD;
+}
+
+/**
+ * xe_pm_init - Initialize Xe Power Management
+ * @xe: xe device instance
+ *
+ * This component is responsible for System and Device sleep states.
+ *
+ * Returns 0 for success, negative error code otherwise.
+ */
+int xe_pm_init(struct xe_device *xe)
+{
+	u32 vram_threshold;
+	int err;
 
 	/* For now suspend/resume is only allowed with GuC */
 	if (!xe_device_uc_enabled(xe))
-		return;
-
-	drmm_mutex_init(&xe->drm, &xe->d3cold.lock);
+		return 0;
 
-	xe->d3cold.capable = xe_pm_pci_d3cold_capable(pdev);
+	xe->d3cold.capable = xe_pm_pci_d3cold_capable(xe);
 
 	if (xe->d3cold.capable) {
-		xe_device_sysfs_init(xe);
-		xe_pm_set_vram_threshold(xe, DEFAULT_VRAM_THRESHOLD);
+		err = xe_device_sysfs_init(xe);
+		if (err)
+			return err;
+
+		vram_threshold = vram_threshold_value(xe);
+		err = xe_pm_set_vram_threshold(xe, vram_threshold);
+		if (err)
+			return err;
 	}
 
 	xe_pm_runtime_init(xe);
+
+	return 0;
 }
 
+/**
+ * xe_pm_runtime_fini - Finalize Runtime PM
+ * @xe: xe device instance
+ */
 void xe_pm_runtime_fini(struct xe_device *xe)
 {
 	struct device *dev = xe->drm.dev;
@@ -212,24 +344,45 @@ struct task_struct *xe_pm_read_callback_task(struct xe_device *xe)
 	return READ_ONCE(xe->pm_callback_task);
 }
 
+/**
+ * xe_pm_runtime_suspended - Check if runtime_pm state is suspended
+ * @xe: xe device instance
+ *
+ * This does not provide any guarantee that the device is going to remain
+ * suspended as it might be racing with the runtime state transitions.
+ * It can be used only as a non-reliable assertion, to ensure that we are not in
+ * the sleep state while trying to access some memory for instance.
+ *
+ * Returns true if PCI device is suspended, false otherwise.
+ */
+bool xe_pm_runtime_suspended(struct xe_device *xe)
+{
+	return pm_runtime_suspended(xe->drm.dev);
+}
+
+/**
+ * xe_pm_runtime_suspend - Prepare our device for D3hot/D3Cold
+ * @xe: xe device instance
+ *
+ * Returns 0 for success, negative error code otherwise.
+ */
 int xe_pm_runtime_suspend(struct xe_device *xe)
 {
+	struct xe_bo *bo, *on;
 	struct xe_gt *gt;
 	u8 id;
 	int err = 0;
 
-	if (xe->d3cold.allowed && xe_device_mem_access_ongoing(xe))
-		return -EBUSY;
-
+	trace_xe_pm_runtime_suspend(xe, __builtin_return_address(0));
 	/* Disable access_ongoing asserts and prevent recursive pm calls */
 	xe_pm_write_callback_task(xe, current);
 
 	/*
-	 * The actual xe_device_mem_access_put() is always async underneath, so
+	 * The actual xe_pm_runtime_put() is always async underneath, so
 	 * exactly where that is called should makes no difference to us. However
 	 * we still need to be very careful with the locks that this callback
 	 * acquires and the locks that are acquired and held by any callers of
-	 * xe_device_mem_access_get(). We already have the matching annotation
+	 * xe_runtime_pm_get(). We already have the matching annotation
 	 * on that side, but we also need it here. For example lockdep should be
 	 * able to tell us if the following scenario is in theory possible:
 	 *
@@ -237,15 +390,27 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
 	 * lock(A)                       |
 	 *                               | xe_pm_runtime_suspend()
 	 *                               |      lock(A)
-	 * xe_device_mem_access_get()    |
+	 * xe_pm_runtime_get()           |
 	 *
 	 * This will clearly deadlock since rpm core needs to wait for
 	 * xe_pm_runtime_suspend() to complete, but here we are holding lock(A)
 	 * on CPU0 which prevents CPU1 making forward progress.  With the
-	 * annotation here and in xe_device_mem_access_get() lockdep will see
+	 * annotation here and in xe_pm_runtime_get() lockdep will see
 	 * the potential lock inversion and give us a nice splat.
 	 */
-	lock_map_acquire(&xe_device_mem_access_lockdep_map);
+	xe_rpm_lockmap_acquire(xe);
+
+	/*
+	 * Applying lock for entire list op as xe_ttm_bo_destroy and xe_bo_move_notify
+	 * also checks and deletes bo entry from user fault list.
+	 */
+	mutex_lock(&xe->mem_access.vram_userfault.lock);
+	list_for_each_entry_safe(bo, on,
+				 &xe->mem_access.vram_userfault.list, vram_userfault_link)
+		xe_bo_runtime_pm_release_mmap_offset(bo);
+	mutex_unlock(&xe->mem_access.vram_userfault.lock);
+
+	xe_display_pm_runtime_suspend(xe);
 
 	if (xe->d3cold.allowed) {
 		err = xe_bo_evict_all(xe);
@@ -260,37 +425,41 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
 	}
 
 	xe_irq_suspend(xe);
+
+	xe_display_pm_runtime_suspend_late(xe);
+
 out:
-	lock_map_release(&xe_device_mem_access_lockdep_map);
+	if (err)
+		xe_display_pm_runtime_resume(xe);
+	xe_rpm_lockmap_release(xe);
 	xe_pm_write_callback_task(xe, NULL);
 	return err;
 }
 
+/**
+ * xe_pm_runtime_resume - Waking up from D3hot/D3Cold
+ * @xe: xe device instance
+ *
+ * Returns 0 for success, negative error code otherwise.
+ */
 int xe_pm_runtime_resume(struct xe_device *xe)
 {
 	struct xe_gt *gt;
 	u8 id;
 	int err = 0;
 
+	trace_xe_pm_runtime_resume(xe, __builtin_return_address(0));
 	/* Disable access_ongoing asserts and prevent recursive pm calls */
 	xe_pm_write_callback_task(xe, current);
 
-	lock_map_acquire(&xe_device_mem_access_lockdep_map);
+	xe_rpm_lockmap_acquire(xe);
 
-	/*
-	 * 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)
-				goto out;
-		}
+	if (xe->d3cold.allowed) {
+		err = xe_pcode_ready(xe, true);
+		if (err)
+			goto out;
+
+		xe_display_pm_resume_early(xe);
 
 		/*
 		 * This only restores pinned memory which is the memory
@@ -306,33 +475,202 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 	for_each_gt(gt, xe, id)
 		xe_gt_resume(gt);
 
-	if (xe->d3cold.allowed && xe->d3cold.power_lost) {
+	xe_display_pm_runtime_resume(xe);
+
+	if (xe->d3cold.allowed) {
 		err = xe_bo_restore_user(xe);
 		if (err)
 			goto out;
 	}
+
 out:
-	lock_map_release(&xe_device_mem_access_lockdep_map);
+	xe_rpm_lockmap_release(xe);
 	xe_pm_write_callback_task(xe, NULL);
 	return err;
 }
 
-int xe_pm_runtime_get(struct xe_device *xe)
+/*
+ * For places where resume is synchronous it can be quite easy to deadlock
+ * if we are not careful. Also in practice it might be quite timing
+ * sensitive to ever see the 0 -> 1 transition with the callers locks
+ * held, so deadlocks might exist but are hard for lockdep to ever see.
+ * With this in mind, help lockdep learn about the potentially scary
+ * stuff that can happen inside the runtime_resume callback by acquiring
+ * a dummy lock (it doesn't protect anything and gets compiled out on
+ * non-debug builds).  Lockdep then only needs to see the
+ * xe_pm_runtime_xxx_map -> runtime_resume callback once, and then can
+ * hopefully validate all the (callers_locks) -> xe_pm_runtime_xxx_map.
+ * For example if the (callers_locks) are ever grabbed in the
+ * runtime_resume callback, lockdep should give us a nice splat.
+ */
+static void xe_rpm_might_enter_cb(const struct xe_device *xe)
+{
+	xe_rpm_lockmap_acquire(xe);
+	xe_rpm_lockmap_release(xe);
+}
+
+/*
+ * Prime the lockdep maps for known locking orders that need to
+ * be supported but that may not always occur on all systems.
+ */
+static void xe_pm_runtime_lockdep_prime(void)
 {
+	struct dma_resv lockdep_resv;
+
+	dma_resv_init(&lockdep_resv);
+	lock_map_acquire(&xe_pm_runtime_d3cold_map);
+	/* D3Cold takes the dma_resv locks to evict bos */
+	dma_resv_lock(&lockdep_resv, NULL);
+	dma_resv_unlock(&lockdep_resv);
+	lock_map_release(&xe_pm_runtime_d3cold_map);
+
+	/* Shrinkers might like to wake up the device under reclaim. */
+	fs_reclaim_acquire(GFP_KERNEL);
+	lock_map_acquire(&xe_pm_runtime_nod3cold_map);
+	lock_map_release(&xe_pm_runtime_nod3cold_map);
+	fs_reclaim_release(GFP_KERNEL);
+}
+
+/**
+ * xe_pm_runtime_get - Get a runtime_pm reference and resume synchronously
+ * @xe: xe device instance
+ */
+void xe_pm_runtime_get(struct xe_device *xe)
+{
+	trace_xe_pm_runtime_get(xe, __builtin_return_address(0));
+	pm_runtime_get_noresume(xe->drm.dev);
+
+	if (xe_pm_read_callback_task(xe) == current)
+		return;
+
+	xe_rpm_might_enter_cb(xe);
+	pm_runtime_resume(xe->drm.dev);
+}
+
+/**
+ * xe_pm_runtime_put - Put the runtime_pm reference back and mark as idle
+ * @xe: xe device instance
+ */
+void xe_pm_runtime_put(struct xe_device *xe)
+{
+	trace_xe_pm_runtime_put(xe, __builtin_return_address(0));
+	if (xe_pm_read_callback_task(xe) == current) {
+		pm_runtime_put_noidle(xe->drm.dev);
+	} else {
+		pm_runtime_mark_last_busy(xe->drm.dev);
+		pm_runtime_put(xe->drm.dev);
+	}
+}
+
+/**
+ * xe_pm_runtime_get_ioctl - Get a runtime_pm reference before ioctl
+ * @xe: xe device instance
+ *
+ * Returns: Any number greater than or equal to 0 for success, negative error
+ * code otherwise.
+ */
+int xe_pm_runtime_get_ioctl(struct xe_device *xe)
+{
+	trace_xe_pm_runtime_get_ioctl(xe, __builtin_return_address(0));
+	if (WARN_ON(xe_pm_read_callback_task(xe) == current))
+		return -ELOOP;
+
+	xe_rpm_might_enter_cb(xe);
 	return pm_runtime_get_sync(xe->drm.dev);
 }
 
-int xe_pm_runtime_put(struct xe_device *xe)
+/**
+ * xe_pm_runtime_get_if_active - Get a runtime_pm reference if device active
+ * @xe: xe device instance
+ *
+ * Return: True if device is awake (regardless the previous number of references)
+ * and a new reference was taken, false otherwise.
+ */
+bool xe_pm_runtime_get_if_active(struct xe_device *xe)
+{
+	return pm_runtime_get_if_active(xe->drm.dev) > 0;
+}
+
+/**
+ * xe_pm_runtime_get_if_in_use - Get a new reference if device is active with previous ref taken
+ * @xe: xe device instance
+ *
+ * Return: True if device is awake, a previous reference had been already taken,
+ * and a new reference was now taken, false otherwise.
+ */
+bool xe_pm_runtime_get_if_in_use(struct xe_device *xe)
 {
-	pm_runtime_mark_last_busy(xe->drm.dev);
-	return pm_runtime_put(xe->drm.dev);
+	if (xe_pm_read_callback_task(xe) == current) {
+		/* The device is awake, grab the ref and move on */
+		pm_runtime_get_noresume(xe->drm.dev);
+		return true;
+	}
+
+	return pm_runtime_get_if_in_use(xe->drm.dev) > 0;
 }
 
-int xe_pm_runtime_get_if_active(struct xe_device *xe)
+/*
+ * Very unreliable! Should only be used to suppress the false positive case
+ * in the missing outer rpm protection warning.
+ */
+static bool xe_pm_suspending_or_resuming(struct xe_device *xe)
 {
-	return pm_runtime_get_if_active(xe->drm.dev, true);
+#ifdef CONFIG_PM
+	struct device *dev = xe->drm.dev;
+
+	return dev->power.runtime_status == RPM_SUSPENDING ||
+		dev->power.runtime_status == RPM_RESUMING ||
+		pm_suspend_target_state != PM_SUSPEND_ON;
+#else
+	return false;
+#endif
 }
 
+/**
+ * xe_pm_runtime_get_noresume - Bump runtime PM usage counter without resuming
+ * @xe: xe device instance
+ *
+ * This function should be used in inner places where it is surely already
+ * protected by outer-bound callers of `xe_pm_runtime_get`.
+ * It will warn if not protected.
+ * The reference should be put back after this function regardless, since it
+ * will always bump the usage counter, regardless.
+ */
+void xe_pm_runtime_get_noresume(struct xe_device *xe)
+{
+	bool ref;
+
+	ref = xe_pm_runtime_get_if_in_use(xe);
+
+	if (!ref) {
+		pm_runtime_get_noresume(xe->drm.dev);
+		drm_WARN(&xe->drm, !xe_pm_suspending_or_resuming(xe),
+			 "Missing outer runtime PM protection\n");
+	}
+}
+
+/**
+ * xe_pm_runtime_resume_and_get - Resume, then get a runtime_pm ref if awake.
+ * @xe: xe device instance
+ *
+ * Returns: True if device is awake and the reference was taken, false otherwise.
+ */
+bool xe_pm_runtime_resume_and_get(struct xe_device *xe)
+{
+	if (xe_pm_read_callback_task(xe) == current) {
+		/* The device is awake, grab the ref and move on */
+		pm_runtime_get_noresume(xe->drm.dev);
+		return true;
+	}
+
+	xe_rpm_might_enter_cb(xe);
+	return pm_runtime_resume_and_get(xe->drm.dev) >= 0;
+}
+
+/**
+ * xe_pm_assert_unbounded_bridge - Disable PM on unbounded pcie parent bridge
+ * @xe: xe device instance
+ */
 void xe_pm_assert_unbounded_bridge(struct xe_device *xe)
 {
 	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
@@ -347,6 +685,13 @@ void xe_pm_assert_unbounded_bridge(struct xe_device *xe)
 	}
 }
 
+/**
+ * xe_pm_set_vram_threshold - Set a vram threshold for allowing/blocking D3Cold
+ * @xe: xe device instance
+ * @threshold: VRAM size in bites for the D3cold threshold
+ *
+ * Returns 0 for success, negative error code otherwise.
+ */
 int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold)
 {
 	struct ttm_resource_manager *man;
@@ -371,6 +716,13 @@ int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold)
 	return 0;
 }
 
+/**
+ * xe_pm_d3cold_allowed_toggle - Check conditions to toggle d3cold.allowed
+ * @xe: xe device instance
+ *
+ * To be called during runtime_pm idle callback.
+ * Check for all the D3Cold conditions ahead of runtime suspend.
+ */
 void xe_pm_d3cold_allowed_toggle(struct xe_device *xe)
 {
 	struct ttm_resource_manager *man;
@@ -399,7 +751,15 @@ void xe_pm_d3cold_allowed_toggle(struct xe_device *xe)
 		xe->d3cold.allowed = false;
 
 	mutex_unlock(&xe->d3cold.lock);
+}
 
-	drm_dbg(&xe->drm,
-		"d3cold: allowed=%s\n", str_yes_no(xe->d3cold.allowed));
+/**
+ * xe_pm_module_init() - Perform xe_pm specific module initialization.
+ *
+ * Return: 0 on success. Currently doesn't fail.
+ */
+int __init xe_pm_module_init(void)
+{
+	xe_pm_runtime_lockdep_prime();
+	return 0;
 }