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SubjectRe: [PATCH v3 01/12] dma: edma: Setup parameters to DMA MAX_NR_SG at a time
On Monday 05 August 2013 09:44 PM, Joel Fernandes wrote:
> Changes are made here for configuring existing parameters to support
> DMA'ing them out in batches as needed.
>
> Also allocate as many as slots as needed by the SG list, but not more
> than MAX_NR_SG. Then these slots will be reused accordingly.
> For ex, if MAX_NR_SG=10, and number of SG entries is 40, still only
> 10 slots will be allocated to DMA the entire SG list of size 40.
>
> Signed-off-by: Joel Fernandes <joelf@ti.com>
> ---
> drivers/dma/edma.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
> index 5f3e532..7b0853c 100644
> --- a/drivers/dma/edma.c
> +++ b/drivers/dma/edma.c
> @@ -222,9 +222,9 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
> enum dma_slave_buswidth dev_width;
> u32 burst;
> struct scatterlist *sg;
> - int i;
> int acnt, bcnt, ccnt, src, dst, cidx;
> int src_bidx, dst_bidx, src_cidx, dst_cidx;
> + int i, num_slots_needed;

'nslots' is more to my liking. Better keep variable names short.

>
> if (unlikely(!echan || !sgl || !sg_len))
> return NULL;
> @@ -262,8 +262,11 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
>
> edesc->pset_nr = sg_len;
>
> - for_each_sg(sgl, sg, sg_len, i) {
> - /* Allocate a PaRAM slot, if needed */
> + /* Allocate a PaRAM slot, if needed */
> +
> + num_slots_needed = sg_len > MAX_NR_SG ? MAX_NR_SG : sg_len;

nslots = min(MAX_NR_SG, sg_len);

> +
> + for (i = 0; i < num_slots_needed; i++) {
> if (echan->slot[i] < 0) {
> echan->slot[i] =
> edma_alloc_slot(EDMA_CTLR(echan->ch_num),
> @@ -273,6 +276,10 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
> return NULL;
> }
> }
> + }
> +
> + /* Configure PaRAM sets for each SG */
> + for_each_sg(sgl, sg, sg_len, i) {
>
> acnt = dev_width;
>
> @@ -330,6 +337,7 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
> /* Configure A or AB synchronized transfers */
> if (edesc->absync)
> edesc->pset[i].opt |= SYNCDIM;
> +

Random extra newline.

The patch as such is fine, but I dont think it makes lot of sense
standalone. This needs to be merged into the patch where you actually
handle the entire SG list in batches.

Thanks,
Sekhar



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