Re: [PATCH 6/7] media: rzv2h-ivc: Avoid double job scheduling

[Barnabás Pőcze]

2026. 03. 13. 12:14 keltezéssel, Jacopo Mondi írta:
> From: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
>
> The scheduling of a new buffer transfer in the IVC driver is triggered
> by two occurrences of the "frame completed" interrupt.
>
> The first interrupt occurrence identifies when all image data have been
> transferred to the ISP, the second occurrence identifies when the
> post-transfer VBLANK has completed and a new buffer can be transferred.
>
> Under heavy system load conditions the actual execution of the workqueue
> item might be delayed and two items might happen to run concurrently,
> leading to a new frame transfer being triggered while the previous one
> has not yet finished.
>
> This error condition is only visible because the driver maintains a
> status variable that counts the number of interrupts since the last
> transfer, and warns in case an IRQ happens before the counter has been
> reset.
>
> To ensure sequential execution of the worqueue items and avoid a double
> buffer transfer to run concurrently, protect the whole function body
> with the spinlock that so far was solely used to reset the counter and
> inspect the interrupt counter variable at the beginning of the buffer
> transfer function.
> and return
>
> As soon as the ongoing transfer completes, the workqueue item will be
> re-scheduled and will consume the pending buffer.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: f0b3984d821b ("media: platform: Add Renesas Input Video Control block driver")
> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
> ---

Looks ok to me.

Reviewed-by: Barnabás Pőcze <barnabas.pocze@xxxxxxxxxxxxxxxx>


>   drivers/media/platform/renesas/rzv2h-ivc/rzv2h-ivc-video.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/platform/renesas/rzv2h-ivc/rzv2h-ivc-video.c b/drivers/media/platform/renesas/rzv2h-ivc/rzv2h-ivc-video.c
> index a22aee0fe1cf..3580a57738a6 100644
> --- a/drivers/media/platform/renesas/rzv2h-ivc/rzv2h-ivc-video.c
> +++ b/drivers/media/platform/renesas/rzv2h-ivc/rzv2h-ivc-video.c
> @@ -149,6 +149,11 @@ static void rzv2h_ivc_transfer_buffer(struct work_struct *work)
>   					     buffers.work);
>   	struct rzv2h_ivc_buf *buf;
>   
> +	guard(spinlock_irqsave)(&ivc->spinlock);
> +
> +	if (ivc->vvalid_ifp)
> +		return;
> +
>   	/* Setup buffers */
>   	scoped_guard(spinlock_irqsave, &ivc->buffers.lock) {
>   		buf = list_first_entry_or_null(&ivc->buffers.queue,
> @@ -163,9 +168,7 @@ static void rzv2h_ivc_transfer_buffer(struct work_struct *work)
>   	buf->addr = vb2_dma_contig_plane_dma_addr(&buf->vb.vb2_buf, 0);
>   	rzv2h_ivc_write(ivc, RZV2H_IVC_REG_AXIRX_SADDL_P0, buf->addr);
>   
> -	scoped_guard(spinlock_irqsave, &ivc->spinlock) {
> -		ivc->vvalid_ifp = 2;
> -	}
> +	ivc->vvalid_ifp = 2;
>   	rzv2h_ivc_write(ivc, RZV2H_IVC_REG_FM_FRCON, 0x1);
>   }
>   
> @@ -200,7 +203,7 @@ static void rzv2h_ivc_buf_queue(struct vb2_buffer *vb)
>   	}
>   
>   	scoped_guard(spinlock_irq, &ivc->spinlock) {
> -		if (vb2_is_streaming(vb->vb2_queue) && !ivc->vvalid_ifp)
> +		if (vb2_is_streaming(vb->vb2_queue))
>   			queue_work(ivc->buffers.async_wq, &ivc->buffers.work);
>   	}
>   }