From: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>

Buffers are programmed into slots in queueing order.

When returning pending buffers we can't simply start from the first slot
but we should actually iterate slots starting from the one is use. The
rzg3e_cru_irq() handler already uses 'active_slot', make rzg2l_cru_irq()
use it as well to know where to start iterating from.

As the pattern of iterating over slots in order will be used for slots
programming in the next patches, provide an helper macro to do that.

While at it, rename return_unused_buffers() to rzg2l_cru_return_buffers().

Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
---
 .../media/platform/renesas/rzg2l-cru/rzg2l-video.c | 68 +++++++++++++++-------
 1 file changed, 47 insertions(+), 21 deletions(-)

diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
index b02940369a18..a5197196a408 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
@@ -42,6 +42,24 @@ struct rzg2l_cru_buffer {
 #define to_buf_list(vb2_buffer) \
 	(&container_of(vb2_buffer, struct rzg2l_cru_buffer, vb)->list)
 
+/*
+ * The CRU hardware cycles over its slots when transferring frames. All drivers
+ * structure that contains programming data for the slots, such as the memory
+ * destination addresses have to be iterated as they were circular buffers.
+ *
+ * Provide here utilities to iterate over slots and the associated data.
+ */
+static inline unsigned int rzg2l_cru_slot_next(struct rzg2l_cru_dev *cru,
+					       unsigned int slot)
+{
+	return (slot + 1) % cru->num_buf;
+}
+
+/* Start cycling on cru slots from the one after 'start'. */
+#define for_each_cru_slot_from(cru, slot, start)			\
+	for (slot = rzg2l_cru_slot_next(cru, start);			\
+	     slot != start; slot = rzg2l_cru_slot_next(cru, slot))
+
 /* -----------------------------------------------------------------------------
  * DMA operations
  */
@@ -105,28 +123,36 @@ __rzg2l_cru_read_constant(struct rzg2l_cru_dev *cru, u32 offset)
 	 __rzg2l_cru_read_constant(cru, offset) : \
 	 __rzg2l_cru_read(cru, offset))
 
-static void return_unused_buffers(struct rzg2l_cru_dev *cru,
-				  enum vb2_buffer_state state)
+static void rzg2l_cru_return_buffers(struct rzg2l_cru_dev *cru,
+				     enum vb2_buffer_state state)
 {
 	struct rzg2l_cru_buffer *buf, *node;
-	unsigned int i;
 
 	scoped_guard(spinlock_irq, &cru->hw_lock) {
-		for (i = 0; i < cru->num_buf; i++) {
-			if (cru->queue_buf[i]) {
-				vb2_buffer_done(&cru->queue_buf[i]->vb2_buf,
-						state);
-				cru->queue_buf[i] = NULL;
-			}
+		/* Return the buffer in progress first, if not completed yet. */
+		unsigned int slot = cru->active_slot;
+
+		if (cru->queue_buf[slot]) {
+			vb2_buffer_done(&cru->queue_buf[slot]->vb2_buf, state);
+			cru->queue_buf[slot] = NULL;
 		}
-	}
 
-	scoped_guard(spinlock_irq, &cru->qlock) {
-		list_for_each_entry_safe(buf, node, &cru->buf_list, list) {
-			vb2_buffer_done(&buf->vb.vb2_buf, state);
-			list_del(&buf->list);
+		/* Return all the pending buffers after the active one. */
+		for_each_cru_slot_from(cru, slot, cru->active_slot) {
+			if (!cru->queue_buf[slot])
+				continue;
+
+			vb2_buffer_done(&cru->queue_buf[slot]->vb2_buf, state);
+			cru->queue_buf[slot] = NULL;
 		}
 	}
+
+	guard(spinlock_irq)(&cru->qlock);
+
+	list_for_each_entry_safe(buf, node, &cru->buf_list, list) {
+		vb2_buffer_done(&buf->vb.vb2_buf, state);
+		list_del(&buf->list);
+	}
 }
 
 static int rzg2l_cru_queue_setup(struct vb2_queue *vq, unsigned int *nbuffers,
@@ -588,16 +614,16 @@ irqreturn_t rzg2l_cru_irq(int irq, void *data)
 
 	/* Prepare for capture and update state */
 	amnmbs = rzg2l_cru_read(cru, AMnMBS);
-	slot = amnmbs & AMnMBS_MBSTS;
+	cru->active_slot = amnmbs & AMnMBS_MBSTS;
 
 	/*
 	 * AMnMBS.MBSTS indicates the destination of Memory Bank (MB).
 	 * Recalculate to get the current transfer complete MB.
 	 */
-	if (slot == 0)
+	if (cru->active_slot == 0)
 		slot = cru->num_buf - 1;
 	else
-		slot--;
+		slot = cru->active_slot - 1;
 
 	/*
 	 * To hand buffers back in a known order to userspace start
@@ -666,7 +692,7 @@ irqreturn_t rzg3e_cru_irq(int irq, void *data)
 	}
 
 	slot = cru->active_slot;
-	cru->active_slot = (cru->active_slot + 1) % cru->num_buf;
+	cru->active_slot = rzg2l_cru_slot_next(cru, cru->active_slot);
 
 	dev_dbg(cru->dev, "Current written slot: %d\n", slot);
 	cru->buf_addr[slot] = 0;
@@ -737,7 +763,7 @@ static int rzg2l_cru_start_streaming_vq(struct vb2_queue *vq, unsigned int count
 	cru->scratch = dma_alloc_coherent(cru->dev, cru->format.sizeimage,
 					  &cru->scratch_phys, GFP_KERNEL);
 	if (!cru->scratch) {
-		return_unused_buffers(cru, VB2_BUF_STATE_QUEUED);
+		rzg2l_cru_return_buffers(cru, VB2_BUF_STATE_QUEUED);
 		dev_err(cru->dev, "Failed to allocate scratch buffer\n");
 		ret = -ENOMEM;
 		goto assert_presetn;
@@ -748,7 +774,7 @@ static int rzg2l_cru_start_streaming_vq(struct vb2_queue *vq, unsigned int count
 
 	ret = rzg2l_cru_set_stream(cru, 1);
 	if (ret) {
-		return_unused_buffers(cru, VB2_BUF_STATE_QUEUED);
+		rzg2l_cru_return_buffers(cru, VB2_BUF_STATE_QUEUED);
 		goto out;
 	}
 
@@ -785,7 +811,7 @@ static void rzg2l_cru_stop_streaming_vq(struct vb2_queue *vq)
 	dma_free_coherent(cru->dev, cru->format.sizeimage,
 			  cru->scratch, cru->scratch_phys);
 
-	return_unused_buffers(cru, VB2_BUF_STATE_ERROR);
+	rzg2l_cru_return_buffers(cru, VB2_BUF_STATE_ERROR);
 
 	reset_control_assert(cru->presetn);
 	clk_disable_unprepare(cru->vclk);

-- 
2.53.0