[PATCH v2 4/4] drm/imagination: Access FW initialised state with READ/WRITE_ONCE

[Brajesh Gupta]

Update FW initialised state shared resource access with READ/WRITE_ONCE
to prevent following:
- Non-atomic access to variable in multi-thread/CPU case.
- Merge successive loads from the same variable.

Signed-off-by: Brajesh Gupta <brajesh.gupta@xxxxxxxxxx>
---
 drivers/gpu/drm/imagination/pvr_device.c |  2 +-
 drivers/gpu/drm/imagination/pvr_fw.c     |  4 ++--
 drivers/gpu/drm/imagination/pvr_mmu.c    |  2 +-
 drivers/gpu/drm/imagination/pvr_power.c  | 10 +++++-----
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_device.c b/drivers/gpu/drm/imagination/pvr_device.c
index 49696101b547..2691ef9af0ca 100644
--- a/drivers/gpu/drm/imagination/pvr_device.c
+++ b/drivers/gpu/drm/imagination/pvr_device.c
@@ -213,7 +213,7 @@ static irqreturn_t pvr_device_irq_thread_handler(int irq, void *data)
 	while (pvr_fw_irq_pending(pvr_dev)) {
 		pvr_fw_irq_clear(pvr_dev);
 
-		if (pvr_dev->fw_dev.initialised) {
+		if (READ_ONCE(pvr_dev->fw_dev.initialised)) {
 			pvr_fwccb_process(pvr_dev);
 			pvr_kccb_wake_up_waiters(pvr_dev);
 			pvr_device_process_active_queues(pvr_dev);
diff --git a/drivers/gpu/drm/imagination/pvr_fw.c b/drivers/gpu/drm/imagination/pvr_fw.c
index b8ad3f1d222c..850a3ec8e775 100644
--- a/drivers/gpu/drm/imagination/pvr_fw.c
+++ b/drivers/gpu/drm/imagination/pvr_fw.c
@@ -1004,7 +1004,7 @@ pvr_fw_init(struct pvr_device *pvr_dev)
 		goto err_fw_stop;
 	}
 
-	fw_dev->initialised = true;
+	WRITE_ONCE(fw_dev->initialised, true);
 
 	return 0;
 
@@ -1044,7 +1044,7 @@ pvr_fw_fini(struct pvr_device *pvr_dev)
 {
 	struct pvr_fw_device *fw_dev = &pvr_dev->fw_dev;
 
-	fw_dev->initialised = false;
+	WRITE_ONCE(fw_dev->initialised, false);
 
 	pvr_fw_destroy_structures(pvr_dev);
 	pvr_fw_object_unmap_and_destroy(pvr_dev->kccb.rtn_obj);
diff --git a/drivers/gpu/drm/imagination/pvr_mmu.c b/drivers/gpu/drm/imagination/pvr_mmu.c
index e9fefcc4e234..3cac482e1034 100644
--- a/drivers/gpu/drm/imagination/pvr_mmu.c
+++ b/drivers/gpu/drm/imagination/pvr_mmu.c
@@ -134,7 +134,7 @@ int pvr_mmu_flush_exec(struct pvr_device *pvr_dev, bool wait)
 		return -EIO;
 
 	/* Can't flush MMU if the firmware hasn't been initialised yet. */
-	if (!pvr_dev->fw_dev.initialised)
+	if (!READ_ONCE(pvr_dev->fw_dev.initialised))
 		goto err_drm_dev_exit;
 
 	cmd_mmu_cache_data->cache_flags =
diff --git a/drivers/gpu/drm/imagination/pvr_power.c b/drivers/gpu/drm/imagination/pvr_power.c
index a73a6815306b..0ed9e7be604b 100644
--- a/drivers/gpu/drm/imagination/pvr_power.c
+++ b/drivers/gpu/drm/imagination/pvr_power.c
@@ -216,7 +216,7 @@ pvr_watchdog_worker(struct work_struct *work)
 	if (pm_runtime_get_if_in_use(from_pvr_device(pvr_dev)->dev) <= 0)
 		goto out_requeue;
 
-	if (!pvr_dev->fw_dev.initialised)
+	if (!READ_ONCE(pvr_dev->fw_dev.initialised))
 		goto out_pm_runtime_put;
 
 	stalled = pvr_watchdog_kccb_stalled(pvr_dev);
@@ -378,7 +378,7 @@ pvr_power_device_suspend(struct device *dev)
 	if (!drm_dev_enter(drm_dev, &idx))
 		return -EIO;
 
-	if (pvr_dev->fw_dev.initialised) {
+	if (READ_ONCE(pvr_dev->fw_dev.initialised)) {
 		err = pvr_power_fw_disable(pvr_dev, false);
 		if (err)
 			goto err_drm_dev_exit;
@@ -408,7 +408,7 @@ pvr_power_device_resume(struct device *dev)
 	if (err)
 		goto err_drm_dev_exit;
 
-	if (pvr_dev->fw_dev.initialised) {
+	if (READ_ONCE(pvr_dev->fw_dev.initialised)) {
 		err = pvr_power_fw_enable(pvr_dev);
 		if (err)
 			goto err_power_off;
@@ -548,7 +548,7 @@ pvr_power_reset(struct pvr_device *pvr_dev, bool hard_reset)
 		err = pvr_power_fw_disable(pvr_dev, hard_reset, false);
 		if (!err) {
 			if (hard_reset) {
-				pvr_dev->fw_dev.initialised = false;
+				WRITE_ONCE(pvr_dev->fw_dev.initialised, false);
 				WARN_ON(pvr_power_device_suspend(from_pvr_device(pvr_dev)->dev));
 
 				err = pvr_fw_hard_reset(pvr_dev);
@@ -556,7 +556,7 @@ pvr_power_reset(struct pvr_device *pvr_dev, bool hard_reset)
 					goto err_device_lost;
 
 				err = pvr_power_device_resume(from_pvr_device(pvr_dev)->dev);
-				pvr_dev->fw_dev.initialised = true;
+				WRITE_ONCE(pvr_dev->fw_dev.initialised, true);
 				if (err)
 					goto err_device_lost;
 			} else {

-- 
2.43.0