Re: [PATCH v4 02/10] dmaengine: Actions: Add support for S700 DMA engine

Vinod Koul
2020-06-24T06:15:36Z

Hi Amit,

On 09-06-20, 15:47, Amit Singh Tomar wrote:

> @@ -372,6 +383,7 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
> struct dma_slave_config *sconfig,
> bool is_cyclic)
> {
> + struct owl_dma *od = to_owl_dma(vchan->vc.chan.device);
> u32 mode, ctrlb;
>
> mode = OWL_DMA_MODE_PW(0);
> @@ -427,14 +439,26 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
> lli->hw[OWL_DMADESC_DADDR] = dst;
> lli->hw[OWL_DMADESC_SRC_STRIDE] = 0;
> lli->hw[OWL_DMADESC_DST_STRIDE] = 0;
> - /*
> - * Word starts from offset 0xC is shared between frame length
> - * (max frame length is 1MB) and frame count, where first 20
> - * bits are for frame length and rest of 12 bits are for frame
> - * count.
> - */
> - lli->hw[OWL_DMADESC_FLEN] = len | FCNT_VAL << 20;
> - lli->hw[OWL_DMADESC_CTRLB] = ctrlb;
> +
> + if (od->devid == S700_DMA) {
> + /* Max frame length is 1MB */
> + lli->hw[OWL_DMADESC_FLEN] = len;
> + /*
> + * On S700, word starts from offset 0x1C is shared between
> + * frame count and ctrlb, where first 12 bits are for frame
> + * count and rest of 20 bits are for ctrlb.
> + */
> + lli->hw[OWL_DMADESC_CTRLB] = FCNT_VAL | ctrlb;
> + } else {
> + /*
> + * On S900, word starts from offset 0xC is shared between
> + * frame length (max frame length is 1MB) and frame count,
> + * where first 20 bits are for frame length and rest of
> + * 12 bits are for frame count.
> + */
> + lli->hw[OWL_DMADESC_FLEN] = len | FCNT_VAL << 20;
> + lli->hw[OWL_DMADESC_CTRLB] = ctrlb;

Unfortunately this wont scale, we will keep adding new conditions for
newer SoC's! So rather than this why not encode max frame length in
driver_data rather than S900_DMA/S700_DMA.. In future one can add values
for newer SoC and not code above logic again.

> +static const struct of_device_id owl_dma_match[] = {
> + { .compatible = "actions,s900-dma", .data = (void *)S900_DMA,},
> + { .compatible = "actions,s700-dma", .data = (void *)S700_DMA,},

Is the .compatible documented, Documentation patch should come before
the driver use patch in a series

> static int owl_dma_probe(struct platform_device *pdev)
> {
> struct device_node *np = pdev->dev.of_node;
> struct owl_dma *od;
> int ret, i, nr_channels, nr_requests;
> + const struct of_device_id *of_id =
> + of_match_device(owl_dma_match, &pdev->dev);

You care about driver_data rather than of_id, so using
of_device_get_match_data() would be better..

> od = devm_kzalloc(&pdev->dev, sizeof(*od), GFP_KERNEL);
> if (!od)
> @@ -1083,6 +1116,8 @@ static int owl_dma_probe(struct platform_device *pdev)
> dev_info(&pdev->dev, "dma-channels %d, dma-requests %d\n",
> nr_channels, nr_requests);
>
> + od->devid = (enum owl_dma_id)(uintptr_t)of_id->data;

Funny casts, I dont think you need uintptr_t!
--
~Vinod