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SubjectRe: [PATCH 1/3] dmaengine: sun6i: Correct DMA support on H3
Hi,

On Thu, Aug 31, 2017 at 01:36:07AM +0200, Stefan Brüns wrote:
> +/* Between SoC generations, there are some significant differences:
> + * - A23 added a clock gate register
> + * - the H3 burst length field has a different offset
> + */

This is not the proper comment style.

> +enum dmac_variant {
> + DMAC_VARIANT_A31,
> + DMAC_VARIANT_A23,
> + DMAC_VARIANT_H3,
> +};
> +

And this is redundant with what we already have in our structures.

> /*
> * Hardware channels / ports representation
> *
> @@ -101,6 +116,7 @@ struct sun6i_dma_config {
> u32 nr_max_channels;
> u32 nr_max_requests;
> u32 nr_max_vchans;
> + enum dmac_variant dmac_variant;
> };
>
> /*
> @@ -240,8 +256,12 @@ static inline s8 convert_burst(u32 maxburst)
> switch (maxburst) {
> case 1:
> return 0;
> + case 4:
> + return 1;
> case 8:
> return 2;
> + case 16:
> + return 3;
> default:
> return -EINVAL;
> }
> @@ -249,11 +269,7 @@ static inline s8 convert_burst(u32 maxburst)
>
> static inline s8 convert_buswidth(enum dma_slave_buswidth addr_width)
> {
> - if ((addr_width < DMA_SLAVE_BUSWIDTH_1_BYTE) ||
> - (addr_width > DMA_SLAVE_BUSWIDTH_4_BYTES))
> - return -EINVAL;
> -
> - return addr_width >> 1;
> + return ilog2(addr_width);
> }

This isn't really the same operation. There should be some explanation
about why it's the right thing to do.

> static size_t sun6i_get_chan_size(struct sun6i_pchan *pchan)
> @@ -499,45 +515,58 @@ static int set_config(struct sun6i_dma_dev *sdev,
> enum dma_transfer_direction direction,
> u32 *p_cfg)
> {
> + enum dma_slave_buswidth src_addr_width, dst_addr_width;
> + u32 src_maxburst, dst_maxburst, supported_burst_length;
> s8 src_width, dst_width, src_burst, dst_burst;
>
> + src_addr_width = sconfig->src_addr_width;
> + dst_addr_width = sconfig->dst_addr_width;
> + src_maxburst = sconfig->src_maxburst;
> + dst_maxburst = sconfig->dst_maxburst;
> +
> + if (sdev->cfg->dmac_variant == DMAC_VARIANT_H3)
> + supported_burst_length = BIT(1) | BIT(4) | BIT(8) | BIT(16);
> + else
> + supported_burst_length = BIT(1) | BIT(8);

This could be stored in the structure for example.

> switch (direction) {
> case DMA_MEM_TO_DEV:
> - src_burst = convert_burst(sconfig->src_maxburst ?
> - sconfig->src_maxburst : 8);
> - src_width = convert_buswidth(sconfig->src_addr_width !=
> - DMA_SLAVE_BUSWIDTH_UNDEFINED ?
> - sconfig->src_addr_width :
> - DMA_SLAVE_BUSWIDTH_4_BYTES);
> - dst_burst = convert_burst(sconfig->dst_maxburst);
> - dst_width = convert_buswidth(sconfig->dst_addr_width);
> + if (src_addr_width == DMA_SLAVE_BUSWIDTH_UNDEFINED)
> + src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + src_maxburst = src_maxburst ? src_maxburst : 8;
> break;
> case DMA_DEV_TO_MEM:
> - src_burst = convert_burst(sconfig->src_maxburst);
> - src_width = convert_buswidth(sconfig->src_addr_width);
> - dst_burst = convert_burst(sconfig->dst_maxburst ?
> - sconfig->dst_maxburst : 8);
> - dst_width = convert_buswidth(sconfig->dst_addr_width !=
> - DMA_SLAVE_BUSWIDTH_UNDEFINED ?
> - sconfig->dst_addr_width :
> - DMA_SLAVE_BUSWIDTH_4_BYTES);
> + if (dst_addr_width == DMA_SLAVE_BUSWIDTH_UNDEFINED)
> + dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dst_maxburst = dst_maxburst ? dst_maxburst : 8;
> break;
> default:
> return -EINVAL;
> }
>
> - if (src_burst < 0)
> - return src_burst;
> - if (src_width < 0)
> - return src_width;
> - if (dst_burst < 0)
> - return dst_burst;
> - if (dst_width < 0)
> - return dst_width;
> -
> - *p_cfg = DMA_CHAN_CFG_SRC_BURST(src_burst) |
> - DMA_CHAN_CFG_SRC_WIDTH(src_width) |
> - DMA_CHAN_CFG_DST_BURST(dst_burst) |
> + if (!(BIT(src_addr_width) & sdev->slave.src_addr_widths))
> + return -EINVAL;
> + if (!(BIT(dst_addr_width) & sdev->slave.dst_addr_widths))
> + return -EINVAL;
> + if (!(BIT(src_maxburst) & supported_burst_length))
> + return -EINVAL;
> + if (!(BIT(dst_maxburst) & supported_burst_length))
> + return -EINVAL;
> +
> + src_width = convert_buswidth(src_addr_width);
> + dst_width = convert_buswidth(dst_addr_width);
> + dst_burst = convert_burst(dst_maxburst);
> + src_burst = convert_burst(src_maxburst);

I'm not sure what you're trying to do here. Could you split your patch
by logical change, this doesn't seem related to just supporting the
H3, but a heavier refactoring.

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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