[PATCH] dmaengine/dw_dmac: Add support for device_prep_dma_sg

[Pratyush Anand]

On 12/23/2011 9:28 PM, Vinod Koul wrote:
> On Tue, 2011-12-13 at 14:17 +0530, Pratyush Anand wrote:
>> Memory to memory copy with scatter gather option has been implemented in
>> this patch. Driver can manage even if number of nodes in src and dst
>> list is different.
> The logic looks okay, but it would be great if we could split this
> prepare here.
> Possibly later when we have multiple such cases we can create templates
> for parsing the non linear sg list and create linear lists from it.
>

Ok. So you suggest to have one patch with a function to align sglist
w.r.t length, and to implement this dwc_prep_dma_sg with aligned list only.

Caller of dwc_prep_dma_sg function will also call something like
align_sg_list(unaligned_dsgl, unaligned ssgl, aligned dsgl,aligned ssgl);
dwc_prep_dma_sg(chan, aligned dsgl, dnents, aligned ssgl, snents, flag);

Is that what you suggest? will do that.

It would be helpful if we can also conclude following discussion.
https://lkml.org/lkml/2011/12/20/95
I am waiting for your reply.

>>
>> Signed-off-by: Pratyush Anand<pratyush.anand at st.com>
>> ---
>>   drivers/dma/dw_dmac.c |  135 +++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 files changed, 135 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
>> index 96b2750..c1c78c1 100644
>> --- a/drivers/dma/dw_dmac.c
>> +++ b/drivers/dma/dw_dmac.c
>> @@ -729,6 +729,140 @@ err_desc_get:
>>   }
>>
>>   static struct dma_async_tx_descriptor *
>> +dwc_prep_dma_sg(struct dma_chan *chan,
>> +	    struct scatterlist *dsgl, unsigned int dst_nents,
>> +	    struct scatterlist *ssgl, unsigned int src_nents,
>> +	    unsigned long flags)
>> +{
>> +	struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
>> +	struct dw_desc *desc;
>> +	struct dw_desc *first;
>> +	struct dw_desc *prev;
>> +	size_t xfer_count;
>> +	size_t offset;
>> +	unsigned int src_width;
>> +	unsigned int dst_width;
>> +	u32 ctllo;
>> +	struct scatterlist *dsg, *ssg;
>> +	dma_addr_t src = 0, dst = 0;
>> +	unsigned int slen = 0, dlen = 0, total_len = 0;
>> +	unsigned int i, nents, len = 0, incs, si = 0, di = 0;
>> +
>> +	if (unlikely(!src_nents))
>> +		return NULL;
>> +
>> +	if (unlikely(!dst_nents))
>> +		return NULL;
>> +
>> +	prev = first = NULL;
>> +
>> +	dsg = dsgl;
>> +	ssg = ssgl;
>> +	nents = max(src_nents, dst_nents);
> shouldn't you validate if total src sg length and dstn sg lengths are
> same here?

Yes, will modify.
Probably we will not need it having aligned sglists.

>> +
>> +	if (nents == src_nents)
>> +		incs = true;
>> +	else
>> +		incs = false;
>> +
>> +	for (i = 0; i<  nents;) {
>> +		if (!slen) {
>> +			src = sg_dma_address(ssg);
>> +			slen = sg_dma_len(ssg);
>> +			ssg = sg_next(ssg);
>> +			if (!ssg&&  si<  src_nents - 1)
>> +				goto err_sg_len;
>> +			si++;
>> +		} else
>> +			src += len;
>> +
>> +		if (!dlen) {
>> +			dst = sg_dma_address(dsg);
>> +			dlen = sg_dma_len(dsg);
>> +			dsg = sg_next(dsg);
>> +			if (!dsg&&  di<  dst_nents - 1)
>> +				goto err_sg_len;
> this could be made better lokking by using helpers

ok. having aligned sglists, logic will be lot simpler.

>
>> +			di++;
>> +		} else
>> +			dst += len;
>> +
>> +		if (incs)
>> +			i = si;
>> +		else
>> +			i = di;
>> +		len = min(slen, dlen);
>> +		slen -= len;
>> +		dlen -= len;
>> +
>> +		if (!((src | dst | len)&  7))
>> +			src_width = dst_width = 3;
>> +		else if (!((src | dst | len)&  3))
>> +			src_width = dst_width = 2;
>> +		else if (!((src | dst | len)&  1))
>> +			src_width = dst_width = 1;
>> +		else
>> +			src_width = dst_width = 0;
> how about putting this is get_me_the_length()

Yes, can do that. Similar logic has been used in other function in this 
file. So may be I need to modify those functions too in a separate patch.

>> +
>> +		ctllo = DWC_DEFAULT_CTLLO(chan->private)
>> +			| DWC_CTLL_DST_WIDTH(dst_width)
>> +			| DWC_CTLL_SRC_WIDTH(src_width)
>> +			| DWC_CTLL_DST_INC
>> +			| DWC_CTLL_SRC_INC
>> +			| DWC_CTLL_FC_M2M;
>> +
>> +		offset = 0;
>> +		while ((len - offset)>  0) {
>> +
>> +			xfer_count = min_t(size_t, (len - offset)>>  dst_width,
>> +					DWC_MAX_COUNT);
>> +
>> +			desc = dwc_desc_get(dwc);
>> +			if (!desc)
>> +				goto err_desc_get;
>> +
>> +			desc->lli.sar = src + offset;
>> +			desc->lli.dar = dst + offset;
>> +			desc->lli.ctllo = ctllo;
>> +			desc->lli.ctlhi = xfer_count;
>> +
>> +			if (!first) {
>> +				first = desc;
>> +			} else {
>> +				prev->lli.llp = desc->txd.phys;
>> +				dma_sync_single_for_device(chan2parent(chan),
>> +						prev->txd.phys,
>> +						sizeof(prev->lli),
>> +						DMA_TO_DEVICE);
>> +				list_add_tail(&desc->desc_node,
>> +						&first->tx_list);
>> +			}
>> +			prev = desc;
>> +			offset += xfer_count<<  dst_width;
>> +		}
>> +		total_len += len;
>> +	}
>> +
>> +	if (flags&  DMA_PREP_INTERRUPT)
>> +		/* Trigger interrupt after last block */
>> +		prev->lli.ctllo |= DWC_CTLL_INT_EN;
>> +
>> +	prev->lli.llp = 0;
>> +	dma_sync_single_for_device(chan2parent(chan),
>> +			prev->txd.phys, sizeof(prev->lli),
>> +			DMA_TO_DEVICE);
>> +
>> +	first->txd.flags = flags;
>> +	first->len = total_len;
>> +
>> +	return&first->txd;
>> +
>> +err_sg_len:
>> +err_desc_get:
>> +	dwc_desc_put(dwc, first);
>> +	return NULL;
>> +}
>> +
>> +static struct dma_async_tx_descriptor *
>>   dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>>   		unsigned int sg_len, enum dma_transfer_direction direction,
>>   		unsigned long flags)
>> @@ -1471,6 +1605,7 @@ static int __init dw_probe(struct platform_device *pdev)
>>   	dw->dma.device_free_chan_resources = dwc_free_chan_resources;
>>
>>   	dw->dma.device_prep_dma_memcpy = dwc_prep_dma_memcpy;
>> +	dw->dma.device_prep_dma_sg = dwc_prep_dma_sg;
>>
>>   	dw->dma.device_prep_slave_sg = dwc_prep_slave_sg;
>>   	dw->dma.device_control = dwc_control;
>> --
>> 1.7.2.2
>>
>>
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>
>