DMA abstaction layer aka xDMA

[br]

Summary

Ideas for improvement:

1. SoftDMA - when we have no real dma yet, but already want to use xDMA
2. Introduce capabilites, so xDMA knows what the transfer types supported by hardware DMA controller, how many data can be copied by single descriptor, etc.
3. Callback provided with some information, e.g. how many data were actually copied and any errors occurred during transfer
4. Scatter-Gathering transfer type (WIP)
5. Non-FDT setup, i.e. real dma controller register itself to xDMA
6. Might be useful to have xdma interrupt thread, so callbacks can be optionally provided not in the interrupt time, but after
7. Requests enqueuing support ? not sure if we need that

[bcr]

I've found a couple of typos in comments.

sys/dev/xdma/xdma.c

422

s/decsriptors/descriptors/

469

s/decsriptors/descriptors/

sys/dev/xdma/xdma_fdt_test.c

311

s/succeded/succeeded/

[br]

fix typos repored by bcr@
add man page

[jmcneill]

sys/dev/xdma/xdma_if.m

66

I think this should be pcell_t

[jmcneill]

Thinking about this some more. For Allwinner (ARM) we have a private sunxi_dma_if that is used. The config structure has some additional fields:

struct sunxi_dma_config {
	unsigned int dst_width;
	unsigned int dst_burst_len;
	unsigned int dst_drqtype;
	bool dst_noincr;
	unsigned int dst_blksize;	/* DDMA-only */
	unsigned int dst_wait_cyc;	/* DDMA-only */
	unsigned int src_width;
	unsigned int src_burst_len;
	unsigned int src_drqtype;
	bool src_noincr;
	unsigned int src_blksize;	/* DDMA-only */
	unsigned int src_wait_cyc;	/* DDMA-only */
};

Is the expectation that as more fields are required we will grow xdma_channel_config?

[br]

Is the expectation that as more fields are required we will grow xdma_channel_config?

Sure! we can grow any time if required.

[br]

use pcell_t instead of phandle_t asnoticed by jmcneill@

sys/dev/xdma/xdma_if.m

66

you right, thanks !