Re: [PATCH 08/14] media: rz2gl-cru: Introduce a spinlock for hw operations

[Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>]

Hi Jacopo,
Thanks for your patch.

On Fri, Mar 27, 2026 at 06:10:13PM +0100, Jacopo Mondi wrote:
> From: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
> 
> The CRU driver uses a single spinlock to protect the buffers queue and
> the hardware operations.
> 
> This single spinlock is held for the whole duration of the interrupt
> handler, causing all other driver's operations to freeze.
> 
> Under heavy system stress conditions with userspace not providing
> buffers fast enough, this causes loss of frames.
> 
> Prepare to re-work the driver locking by introducing (but not using yet)
> a new spinlock to protect the hardware registers programming.
> 

Reviewed-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>

Kind Regards,
Tommaso

> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
> ---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-cru.h   | 10 +++++++---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c |  1 +
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-cru.h b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-cru.h
> index 3a200db15730..b46696a0012b 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-cru.h
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-cru.h
> @@ -109,7 +109,6 @@ struct rzg2l_cru_info {
>   * @v4l2_dev:		V4L2 device
>   * @num_buf:		Holds the current number of buffers enabled
>   * @svc_channel:	SVC0/1/2/3 to use for RZ/G3E
> - * @buf_addr:		Memory addresses where current video data is written.
>   * @notifier:		V4L2 asynchronous subdevs notifier
>   *
>   * @ip:			Image processing subdev info
> @@ -118,6 +117,10 @@ struct rzg2l_cru_info {
>   * @mdev_lock:		protects the count, notifier and csi members
>   * @pad:		media pad for the video device entity
>   *
> + * @hw_lock:		protects the slot counter, hardware programming of
> + *			slot addresses and the @buf_addr[] list
> + * @buf_addr:		Memory addresses where current video data is written
> + *
>   * @lock:		protects @queue
>   * @queue:		vb2 buffers queue
>   * @scratch:		cpu address for scratch buffer
> @@ -147,8 +150,6 @@ struct rzg2l_cru_dev {
>  	u8 num_buf;
>  
>  	u8 svc_channel;
> -	dma_addr_t buf_addr[RZG2L_CRU_HW_BUFFER_DEFAULT];
> -
>  	struct v4l2_async_notifier notifier;
>  
>  	struct rzg2l_cru_ip ip;
> @@ -157,6 +158,9 @@ struct rzg2l_cru_dev {
>  	struct mutex mdev_lock;
>  	struct media_pad pad;
>  
> +	spinlock_t hw_lock;
> +	dma_addr_t buf_addr[RZG2L_CRU_HW_BUFFER_DEFAULT];
> +
>  	struct mutex lock;
>  	struct vb2_queue queue;
>  	void *scratch;
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 27079c17a54c..a79b17e146bf 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -844,6 +844,7 @@ int rzg2l_cru_dma_register(struct rzg2l_cru_dev *cru)
>  	mutex_init(&cru->lock);
>  	INIT_LIST_HEAD(&cru->buf_list);
>  
> +	spin_lock_init(&cru->hw_lock);
>  	spin_lock_init(&cru->qlock);
>  
>  	cru->state = RZG2L_CRU_DMA_STOPPED;
> 
> -- 
> 2.53.0
>