Re: [PATCH 2/3] rcar-vin: allocate a scratch buffer at stream start

[jacopo mondi <jacopo@jmondi.org>]

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Hi Niklas,

On Sat, Mar 10, 2018 at 01:09:52AM +0100, Niklas Söderlund wrote:
> Before starting capturing allocate a scratch buffer which can be used by
> the driver to give to the hardware if no buffers are available from
> userspace. The buffer is not used in this patch but prepares for future
> refactoring where the scratch buffer can be used to avoid the need to
> fallback on single capture mode if userspace don't queue buffers as fast
> as the VIN driver consumes them.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
>  drivers/media/platform/rcar-vin/rcar-dma.c | 19 +++++++++++++++++++
>  drivers/media/platform/rcar-vin/rcar-vin.h |  4 ++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-dma.c b/drivers/media/platform/rcar-vin/rcar-dma.c
> index b4be75d5009080f7..8ea73cdc9a720abe 100644
> --- a/drivers/media/platform/rcar-vin/rcar-dma.c
> +++ b/drivers/media/platform/rcar-vin/rcar-dma.c
> @@ -1070,6 +1070,17 @@ static int rvin_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	unsigned long flags;
>  	int ret;
>
> +	/* Allocate scratch buffer. */
> +	vin->scratch = dma_alloc_coherent(vin->dev, vin->format.sizeimage,
> +					  &vin->scratch_phys, GFP_KERNEL);
> +	if (!vin->scratch) {
> +		spin_lock_irqsave(&vin->qlock, flags);
> +		return_all_buffers(vin, VB2_BUF_STATE_QUEUED);
> +		spin_unlock_irqrestore(&vin->qlock, flags);
> +		vin_err(vin, "Failed to allocate scratch buffer\n");
> +		return -ENOMEM;
> +	}
> +
>  	sd = vin_to_source(vin);
>  	v4l2_subdev_call(sd, video, s_stream, 1);
>
> @@ -1085,6 +1096,10 @@ static int rvin_start_streaming(struct vb2_queue *vq, unsigned int count)
>
>  	spin_unlock_irqrestore(&vin->qlock, flags);
>
> +	if (ret)
> +		dma_free_coherent(vin->dev, vin->format.sizeimage, vin->scratch,
> +				  vin->scratch_phys);
> +
>  	return ret;
>  }
>
> @@ -1135,6 +1150,10 @@ static void rvin_stop_streaming(struct vb2_queue *vq)
>
>  	/* disable interrupts */
>  	rvin_disable_interrupts(vin);
> +
> +	/* Free scratch buffer. */
> +	dma_free_coherent(vin->dev, vin->format.sizeimage, vin->scratch,
> +			  vin->scratch_phys);
>  }
>
>  static const struct vb2_ops rvin_qops = {
> diff --git a/drivers/media/platform/rcar-vin/rcar-vin.h b/drivers/media/platform/rcar-vin/rcar-vin.h
> index 5382078143fb3869..11a981d707c7ca47 100644
> --- a/drivers/media/platform/rcar-vin/rcar-vin.h
> +++ b/drivers/media/platform/rcar-vin/rcar-vin.h
> @@ -102,6 +102,8 @@ struct rvin_graph_entity {
>   *
>   * @lock:		protects @queue
>   * @queue:		vb2 buffers queue
> + * @scratch:		cpu address for scratch buffer
> + * @scratch_phys:	pysical address of the scratch buffer

Nitpicking: physical

Thanks
   j

>   *
>   * @qlock:		protects @queue_buf, @buf_list, @continuous, @sequence
>   *			@state
> @@ -130,6 +132,8 @@ struct rvin_dev {
>
>  	struct mutex lock;
>  	struct vb2_queue queue;
> +	void *scratch;
> +	dma_addr_t scratch_phys;
>
>  	spinlock_t qlock;
>  	struct vb2_v4l2_buffer *queue_buf[HW_BUFFER_NUM];
> --
> 2.16.2
>

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