Re: [PATCH 13/16] media: ti-vpe: csi2rx: Add CSI2RX support

["Péter Ujfalusi" <peter.ujfalusi@gmail.com>]

Hi Pratyush,

+1 from me also to the points Tomi raised.

few minor comments on the DMAengie side.

On 3/30/21 8:33 PM, Pratyush Yadav wrote:
> TI's J721E uses the Cadence CSI2RX and DPHY peripherals to facilitate
> capture over a CSI-2 bus.
> 
> The Cadence CSI2RX IP acts as a bridge between the TI specific parts and
> the CSI-2 protocol parts. TI then has a wrapper on top of this bridge
> called the SHIM layer. It takes in data from stream 0, repacks it, and
> sends it to memory over PSI-L DMA.
> 
> This driver acts as the "front end" to V4L2 client applications. It
> implements the required ioctls and buffer operations, passes the
> necessary calls on to the bridge, programs the SHIM layer, and performs
> DMA via the dmaengine API to finally return the data to a buffer
> supplied by the application.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> ---
>  MAINTAINERS                               |   7 +
>  drivers/media/platform/Kconfig            |  11 +
>  drivers/media/platform/ti-vpe/Makefile    |   1 +
>  drivers/media/platform/ti-vpe/ti-csi2rx.c | 964 ++++++++++++++++++++++
>  4 files changed, 983 insertions(+)
>  create mode 100644 drivers/media/platform/ti-vpe/ti-csi2rx.c

...

> diff --git a/drivers/media/platform/ti-vpe/ti-csi2rx.c b/drivers/media/platform/ti-vpe/ti-csi2rx.c
> new file mode 100644
> index 000000000000..355204ae473b
> --- /dev/null
> +++ b/drivers/media/platform/ti-vpe/ti-csi2rx.c

...

> +static int ti_csi2rx_init_vb2q(struct ti_csi2rx_dev *csi)
> +{
> +	struct vb2_queue *q = &csi->vidq;
> +	int ret;
> +
> +	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> +	q->io_modes = VB2_MMAP | VB2_USERPTR | VB2_DMABUF | VB2_READ;
> +	q->drv_priv = csi;
> +	q->buf_struct_size = sizeof(struct ti_csi2rx_buffer);
> +	q->ops = &csi_vb2_qops;
> +	q->mem_ops = &vb2_dma_contig_memops;
> +	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> +	q->dev = csi->dma->device->dev;

q->dev = dmaengine_get_dma_device(csi->dma);

> +	q->lock = &csi->mutex;
> +
> +	ret = vb2_queue_init(q);
> +	if (ret)
> +		return ret;
> +
> +	csi->vdev.queue = q;
> +
> +	return 0;
> +}
> +
> +static int ti_csi2rx_init_dma(struct ti_csi2rx_dev *csi)
> +{
> +	struct dma_slave_config cfg;
> +	int ret;
> +
> +	INIT_LIST_HEAD(&csi->dmaq.list);
> +
> +	csi->dma = NULL;
> +
> +	csi->dma = dma_request_chan(csi->dev, "rx0");
> +	if (IS_ERR(csi->dma))
> +		return PTR_ERR(csi->dma);
> +
> +	memset(&cfg, 0, sizeof(cfg));
> +
> +	cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_16_BYTES;
> +	cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_16_BYTES;

No need to set the dst_addr_width as you only support RX.

Another note: UDMA with PSI-L native peripherals ignores this
cofniguration, only used for PDMAs, but I can remain to future proof the
driver and to keep it generic.

> +
> +	ret = dmaengine_slave_config(csi->dma, &cfg);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}

-- 
Péter