drm/msm: Document and rename preempt_lock

[ Upstream commit 77c406038e ]

Before adding another lock, give ring->lock a more descriptive name.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Stable-dep-of: b4fb748f0b ("drm/msm/a5xx: fix the emptyness check in the preempt code")
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/msm/adreno/a5xx_gpu.c

@@ -36,7 +36,7 @@ void a5xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
 		OUT_RING(ring, upper_32_bits(shadowptr(a5xx_gpu, ring)));
 	}
 
-	spin_lock_irqsave(&ring->lock, flags);
+	spin_lock_irqsave(&ring->preempt_lock, flags);
 
 	/* Copy the shadow to the actual register */
 	ring->cur = ring->next;
@@ -44,7 +44,7 @@ void a5xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
 	/* Make sure to wrap wptr if we need to */
 	wptr = get_wptr(ring);
 
-	spin_unlock_irqrestore(&ring->lock, flags);
+	spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 	/* Make sure everything is posted before making a decision */
 	mb();

drivers/gpu/drm/msm/adreno/a5xx_preempt.c

@@ -45,9 +45,9 @@ static inline void update_wptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 	if (!ring)
 		return;
 
-	spin_lock_irqsave(&ring->lock, flags);
+	spin_lock_irqsave(&ring->preempt_lock, flags);
 	wptr = get_wptr(ring);
-	spin_unlock_irqrestore(&ring->lock, flags);
+	spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 	gpu_write(gpu, REG_A5XX_CP_RB_WPTR, wptr);
 }
@@ -62,9 +62,9 @@ static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
 		bool empty;
 		struct msm_ringbuffer *ring = gpu->rb[i];
 
-		spin_lock_irqsave(&ring->lock, flags);
+		spin_lock_irqsave(&ring->preempt_lock, flags);
 		empty = (get_wptr(ring) == ring->memptrs->rptr);
-		spin_unlock_irqrestore(&ring->lock, flags);
+		spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 		if (!empty)
 			return ring;
@@ -132,9 +132,9 @@ void a5xx_preempt_trigger(struct msm_gpu *gpu)
 	}
 
 	/* Make sure the wptr doesn't update while we're in motion */
-	spin_lock_irqsave(&ring->lock, flags);
+	spin_lock_irqsave(&ring->preempt_lock, flags);
 	a5xx_gpu->preempt[ring->id]->wptr = get_wptr(ring);
-	spin_unlock_irqrestore(&ring->lock, flags);
+	spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 	/* Set the address of the incoming preemption record */
 	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_LO,

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

@@ -65,7 +65,7 @@ static void a6xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 		OUT_RING(ring, upper_32_bits(shadowptr(a6xx_gpu, ring)));
 	}
 
-	spin_lock_irqsave(&ring->lock, flags);
+	spin_lock_irqsave(&ring->preempt_lock, flags);
 
 	/* Copy the shadow to the actual register */
 	ring->cur = ring->next;
@@ -73,7 +73,7 @@ static void a6xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 	/* Make sure to wrap wptr if we need to */
 	wptr = get_wptr(ring);
 
-	spin_unlock_irqrestore(&ring->lock, flags);
+	spin_unlock_irqrestore(&ring->preempt_lock, flags);
 
 	/* Make sure everything is posted before making a decision */
 	mb();

drivers/gpu/drm/msm/msm_ringbuffer.c

@@ -46,7 +46,7 @@ struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
 	ring->memptrs_iova = memptrs_iova;
 
 	INIT_LIST_HEAD(&ring->submits);
-	spin_lock_init(&ring->lock);
+	spin_lock_init(&ring->preempt_lock);
 
 	snprintf(name, sizeof(name), "gpu-ring-%d", ring->id);
 

drivers/gpu/drm/msm/msm_ringbuffer.h

@@ -46,7 +46,12 @@ struct msm_ringbuffer {
 	struct msm_rbmemptrs *memptrs;
 	uint64_t memptrs_iova;
 	struct msm_fence_context *fctx;
-	spinlock_t lock;
+
+	/*
+	 * preempt_lock protects preemption and serializes wptr updates against
+	 * preemption.  Can be aquired from irq context.
+	 */
+	spinlock_t preempt_lock;
 };
 
 struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,