Re: [PATCH 07/10] dmaengine: sun6i: Retrieve channel count/max request from devicetree

André Przywara
2017-09-03T23:48:36Z

Hi,

On 03/09/17 23:40, Stefan Brüns wrote:
> To avoid introduction of a new compatible for each small SoC/DMA controller
> variation, move the definition of the channel count to the devicetree.
>
> The number of vchans is no longer explicit, but limited by the highest
> port/DMA request number. The result is a slight overallocation for SoCs
> with a sparse port mapping.
>
> Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
> ---
> drivers/dma/sun6i-dma.c | 35 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index c69dadb853d2..bd4c2e4a759b 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -42,6 +42,9 @@
>
> #define DMA_STAT 0x30
>
> +/* Offset between DMA_IRQ_EN and DMA_IRQ_STAT limits number of channels */
> +#define DMA_MAX_CHANNELS (DMA_IRQ_CHAN_NR * 0x10 / 4)
> +
> /*
> * sun8i specific registers
> */
> @@ -65,7 +68,8 @@
> #define DMA_CHAN_LLI_ADDR 0x08
>
> #define DMA_CHAN_CUR_CFG 0x0c
> -#define DMA_CHAN_CFG_SRC_DRQ(x) ((x) & 0x1f)
> +#define DMA_CHAN_MAX_DRQ 0x1f
> +#define DMA_CHAN_CFG_SRC_DRQ(x) ((x) & DMA_CHAN_MAX_DRQ)
> #define DMA_CHAN_CFG_SRC_IO_MODE BIT(5)
> #define DMA_CHAN_CFG_SRC_LINEAR_MODE (0 << 5)
> #define DMA_CHAN_CFG_SRC_BURST_A31(x) (((x) & 0x3) << 7)
> @@ -1173,6 +1177,35 @@ static int sun6i_dma_probe(struct platform_device *pdev)
> sdc->num_vchans = sdc->cfg->nr_max_vchans;
> sdc->max_request = sdc->cfg->nr_max_requests;
>
> + ret = of_property_read_u32(np, "dma-channels", &sdc->num_pchans);
> + if (ret && !sdc->num_pchans) {
> + dev_err(&pdev->dev, "Can't get dma-channels.\n");
> + return ret;
> + }
> +
> + if (sdc->num_pchans > DMA_MAX_CHANNELS) {
> + dev_err(&pdev->dev, "Number of dma-channels out of range.\n");
> + return -EINVAL;
> + }
> +
> + ret = of_property_read_u32(np, "dma-requests", &sdc->max_request);
> + if (ret && !sdc->max_request) {
> + dev_info(&pdev->dev, "Missing dma-requests, using %u.\n",
> + DMA_CHAN_MAX_DRQ);

Mmmh, is this mapping of "!sdc->max_request" -> DMA_CHAN_MAX_DRQ
implemented somewhere else? Or is it just missing here:
sdc->max_request = DMA_CHAN_MAX_DRQ;

Otherwise this is looking good, thanks for picking up the DT property
approach!

Cheers,
Andre.

> + }
> +
> + if (sdc->max_request > DMA_CHAN_MAX_DRQ) {
> + dev_err(&pdev->dev, "Value of dma-requests out of range.\n");
> + return -EINVAL;
> + }
> +
> + /*
> + * If the number of vchans is not specified, derive it from the
> + * highest port number, at most one channel per port and direction.
> + */
> + if (!sdc->num_vchans)
> + sdc->num_vchans = 2 * (sdc->max_request + 1);
> +
> sdc->pchans = devm_kcalloc(&pdev->dev, sdc->num_pchans,
> sizeof(struct sun6i_pchan), GFP_KERNEL);
> if (!sdc->pchans)
>