[Intel-xe] [PATCH v4 1/6] Revert "drm/xe: Use atomic instead of mutex for xe_device_mem_access_ongoing"

[Matthew Auld]

This reverts commit c3712d924f6b5022498f4357009943c326389f9c.

We add a similar version back, once we fix the locking inside
xe_device_mem_access.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/xe/xe_device.c       | 18 ++++++++++--------
 drivers/gpu/drm/xe/xe_device.h       | 18 ++++++++++++------
 drivers/gpu/drm/xe/xe_device_types.h |  4 +++-
 3 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index f7f6a6a97757..d0297ee432b2 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -216,6 +216,8 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	if (err)
 		goto err_put;
 
+	drmm_mutex_init(&xe->drm, &xe->mem_access.lock);
+
 	return xe;
 
 err_put:
@@ -404,25 +406,25 @@ u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size)
 void xe_device_mem_access_get(struct xe_device *xe)
 {
 	bool resumed = xe_pm_runtime_resume_if_suspended(xe);
-	int ref = atomic_inc_return(&xe->mem_access.ref);
 
-	if (ref == 1)
+	mutex_lock(&xe->mem_access.lock);
+	if (xe->mem_access.ref++ == 0)
 		xe->mem_access.hold_rpm = xe_pm_runtime_get_if_active(xe);
+	mutex_unlock(&xe->mem_access.lock);
 
 	/* The usage counter increased if device was immediately resumed */
 	if (resumed)
 		xe_pm_runtime_put(xe);
 
-	XE_WARN_ON(ref == S32_MAX);
+	XE_WARN_ON(xe->mem_access.ref == S32_MAX);
 }
 
 void xe_device_mem_access_put(struct xe_device *xe)
 {
-	bool hold = xe->mem_access.hold_rpm;
-	int ref = atomic_dec_return(&xe->mem_access.ref);
-
-	if (!ref && hold)
+	mutex_lock(&xe->mem_access.lock);
+	if (--xe->mem_access.ref == 0 && xe->mem_access.hold_rpm)
 		xe_pm_runtime_put(xe);
+	mutex_unlock(&xe->mem_access.lock);
 
-	XE_WARN_ON(ref < 0);
+	XE_WARN_ON(xe->mem_access.ref < 0);
 }
diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
index cbae480a2092..9ab7e6134f89 100644
--- a/drivers/gpu/drm/xe/xe_device.h
+++ b/drivers/gpu/drm/xe/xe_device.h
@@ -90,14 +90,20 @@ static inline struct xe_force_wake * gt_to_fw(struct xe_gt *gt)
 void xe_device_mem_access_get(struct xe_device *xe);
 void xe_device_mem_access_put(struct xe_device *xe);
 
-static inline bool xe_device_mem_access_ongoing(struct xe_device *xe)
-{
-	return atomic_read(&xe->mem_access.ref);
-}
-
 static inline void xe_device_assert_mem_access(struct xe_device *xe)
 {
-	XE_WARN_ON(!xe_device_mem_access_ongoing(xe));
+	XE_WARN_ON(!xe->mem_access.ref);
+}
+
+static inline bool xe_device_mem_access_ongoing(struct xe_device *xe)
+{
+	bool ret;
+
+	mutex_lock(&xe->mem_access.lock);
+	ret = xe->mem_access.ref;
+	mutex_unlock(&xe->mem_access.lock);
+
+	return ret;
 }
 
 static inline bool xe_device_in_fault_mode(struct xe_device *xe)
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 6490a04614ce..d91193c41d2e 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -256,8 +256,10 @@ struct xe_device {
 	 * triggering additional actions when they occur.
 	 */
 	struct {
+		/** @lock: protect the ref count */
+		struct mutex lock;
 		/** @ref: ref count of memory accesses */
-		atomic_t ref;
+		s32 ref;
 		/** @hold_rpm: need to put rpm ref back at the end */
 		bool hold_rpm;
 	} mem_access;
-- 
2.40.1