On Thu Sep 18 12:02:06 2025 +0100, Daniel Scally wrote:
> The current implementation of rzg2l_cru_fill_hw_slot() results in the
> artificial loss of frames. At present whenever a frame-complete IRQ
> is received the driver fills the hardware slot that was just written
> to with the address of the next buffer in the driver's queue. If the
> queue is empty, that hardware slot's address is set to the address of
> the scratch buffer to enable the capture loop to keep running. There
> is a minimum of a two-frame delay before that slot will be written to
> however, and in the intervening period userspace may queue more
> buffers which could be used.
>
> To resolve the issue rework rzg2l_cru_fill_hw_slot() so that it
> iteratively fills all slots from the queue which currently do not
> have a buffer assigned, until the queue is empty. The scratch
> buffer is only resorted to in the event that the queue is empty and
> the next slot that will be written to does not already have a buffer
> assigned.
>
> Signed-off-by: Daniel Scally <[email protected]>
> Signed-off-by: Jacopo Mondi <[email protected]>
> Tested-by: Tommaso Merciai <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
.../media/platform/renesas/rzg2l-cru/rzg2l-video.c | 64 +++++++++++++---------
1 file changed, 37 insertions(+), 27 deletions(-)
---
diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
index 715628878b90..c375cf9e261e 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
@@ -214,47 +214,52 @@ static void rzg2l_cru_set_slot_addr(struct rzg2l_cru_dev
*cru,
}
/*
- * Moves a buffer from the queue to the HW slot. If no buffer is
- * available use the scratch buffer. The scratch buffer is never
- * returned to userspace, its only function is to enable the capture
- * loop to keep running.
+ * Move as many buffers as possible from the queue to HW slots If no buffer is
+ * available use the scratch buffer. The scratch buffer is never returned to
+ * userspace, its only function is to enable the capture loop to keep running.
+ *
+ * @cru: the CRU device
+ * @slot: the slot that has just completed
*/
static void rzg2l_cru_fill_hw_slot(struct rzg2l_cru_dev *cru, int slot)
{
- struct vb2_v4l2_buffer *vbuf;
struct rzg2l_cru_buffer *buf;
+ struct vb2_v4l2_buffer *vbuf;
+ unsigned int next_slot;
dma_addr_t phys_addr;
- /* A already populated slot shall never be overwritten. */
- if (WARN_ON(cru->queue_buf[slot]))
- return;
+ lockdep_assert_held(&cru->hw_lock);
- dev_dbg(cru->dev, "Filling HW slot: %d\n", slot);
+ /* Find the next slot which hasn't a valid address programmed. */
+ for_each_cru_slot_from(cru, next_slot, slot) {
+ if (cru->queue_buf[next_slot])
+ continue;
- guard(spinlock)(&cru->qlock);
+ scoped_guard(spinlock_irqsave, &cru->qlock) {
+ buf = list_first_entry_or_null(&cru->buf_list,
+ struct rzg2l_cru_buffer,
list);
+ if (buf)
+ list_del_init(&buf->list);
+ }
- if (list_empty(&cru->buf_list)) {
- cru->queue_buf[slot] = NULL;
- phys_addr = cru->scratch_phys;
- } else {
- /* Keep track of buffer we give to HW */
- buf = list_entry(cru->buf_list.next,
- struct rzg2l_cru_buffer, list);
- vbuf = &buf->vb;
- list_del_init(to_buf_list(vbuf));
- cru->queue_buf[slot] = vbuf;
+ if (!buf) {
+ /* Direct frames to the scratch buffer. */
+ phys_addr = cru->scratch_phys;
+ cru->queue_buf[next_slot] = NULL;
+ rzg2l_cru_set_slot_addr(cru, next_slot, phys_addr);
+ return;
+ }
- /* Setup DMA */
+ vbuf = &buf->vb;
+ cru->queue_buf[next_slot] = vbuf;
phys_addr = vb2_dma_contig_plane_dma_addr(&vbuf->vb2_buf, 0);
+ rzg2l_cru_set_slot_addr(cru, next_slot, phys_addr);
}
-
- rzg2l_cru_set_slot_addr(cru, slot, phys_addr);
}
static void rzg2l_cru_initialize_axi(struct rzg2l_cru_dev *cru)
{
const struct rzg2l_cru_info *info = cru->info;
- unsigned int slot;
u32 amnaxiattr;
/*
@@ -263,8 +268,14 @@ static void rzg2l_cru_initialize_axi(struct rzg2l_cru_dev
*cru)
*/
rzg2l_cru_write(cru, AMnMBVALID, AMnMBVALID_MBVALID(cru->num_buf - 1));
- for (slot = 0; slot < cru->num_buf; slot++)
- rzg2l_cru_fill_hw_slot(cru, slot);
+ /*
+ * Program slot#0 with the first available buffer, if any. Pass to the
+ * function 'num_buf - 1' as rzg2l_cru_fill_hw_slot() calculates which
+ * is the next slot to program.
+ */
+ scoped_guard(spinlock_irq, &cru->hw_lock) {
+ rzg2l_cru_fill_hw_slot(cru, cru->num_buf - 1);
+ }
if (info->has_stride) {
u32 stride = cru->format.bytesperline;
@@ -695,7 +706,6 @@ irqreturn_t rzg3e_cru_irq(int irq, void *data)
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;
/*
* To hand buffers back in a known order to userspace start
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