[PATCH 2/3] drm/panthor: Revisit reqs_lock handling in flush/reset paths

[Nicolas Frattaroli]

panthor_gpu_flush_caches() and panthor_gpu_soft_reset() would read (and
even reset) the contents of the pending_reqs register outside of holding
the reqs_lock. Additionally, when it did hold the lock, it did so with
the irqsave/irqrestore variants, even though the spinlock was never
acquired in an atomic context, just the threaded handler.

Use the new wait_event_lock_timeout() macro to check pending_reqs under
the lock, and only do so without disabling interrupts.

Fixes: 5cd894e258c4 ("drm/panthor: Add the GPU logical block")
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/panthor/panthor_gpu.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
index c013d6bf9a59..f015bde80abf 100644
--- a/drivers/gpu/drm/panthor/panthor_gpu.c
+++ b/drivers/gpu/drm/panthor/panthor_gpu.c
@@ -330,35 +330,34 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev,
 			     u32 l2, u32 lsc, u32 other)
 {
 	struct panthor_gpu *gpu = ptdev->gpu;
-	unsigned long flags;
 	int ret = 0;
 
 	/* Serialize cache flush operations. */
 	guard(mutex)(&ptdev->gpu->cache_flush_lock);
 
-	spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
+	spin_lock(&ptdev->gpu->reqs_lock);
 	if (!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED)) {
 		ptdev->gpu->pending_reqs |= GPU_IRQ_CLEAN_CACHES_COMPLETED;
 		gpu_write(gpu->iomem, GPU_CMD, GPU_FLUSH_CACHES(l2, lsc, other));
 	} else {
 		ret = -EIO;
 	}
-	spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
 
-	if (ret)
+	if (ret) {
+		spin_unlock(&ptdev->gpu->reqs_lock);
 		return ret;
+	}
 
-	if (!wait_event_timeout(ptdev->gpu->reqs_acked,
+	if (!wait_event_lock_timeout(ptdev->gpu->reqs_acked,
 				!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED),
-				msecs_to_jiffies(100))) {
-		spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
+				ptdev->gpu->reqs_lock, msecs_to_jiffies(100))) {
 		if ((ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED) != 0 &&
 		    !(gpu_read(gpu->irq.iomem, INT_RAWSTAT) & GPU_IRQ_CLEAN_CACHES_COMPLETED))
 			ret = -ETIMEDOUT;
 		else
 			ptdev->gpu->pending_reqs &= ~GPU_IRQ_CLEAN_CACHES_COMPLETED;
-		spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
 	}
+	spin_unlock(&ptdev->gpu->reqs_lock);
 
 	if (ret) {
 		panthor_device_schedule_reset(ptdev);
@@ -378,27 +377,25 @@ int panthor_gpu_soft_reset(struct panthor_device *ptdev)
 {
 	struct panthor_gpu *gpu = ptdev->gpu;
 	bool timedout = false;
-	unsigned long flags;
 
-	spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
+	guard(spinlock)(&ptdev->gpu->reqs_lock);
+
 	if (!drm_WARN_ON(&ptdev->base,
 			 ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED)) {
 		ptdev->gpu->pending_reqs |= GPU_IRQ_RESET_COMPLETED;
 		gpu_write(gpu->irq.iomem, INT_CLEAR, GPU_IRQ_RESET_COMPLETED);
 		gpu_write(gpu->iomem, GPU_CMD, GPU_SOFT_RESET);
 	}
-	spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
 
-	if (!wait_event_timeout(ptdev->gpu->reqs_acked,
+	if (!wait_event_lock_timeout(ptdev->gpu->reqs_acked,
 				!(ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED),
+				ptdev->gpu->reqs_lock,
 				msecs_to_jiffies(100))) {
-		spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
 		if ((ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED) != 0 &&
 		    !(gpu_read(gpu->irq.iomem, INT_RAWSTAT) & GPU_IRQ_RESET_COMPLETED))
 			timedout = true;
 		else
 			ptdev->gpu->pending_reqs &= ~GPU_IRQ_RESET_COMPLETED;
-		spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
 	}
 
 	if (timedout) {

-- 
2.55.0