On Tue, Apr 28, 2015 at 11:03:22AM +0200, Maxime Ripard wrote:
> So far, we were setting the NDE bit in our descriptors through some logic to
> try to see if we were the last descriptor in the chain.
>
> However, that was turning out to be rather complex to get right, while this
> information is also available when we actually chain a new descriptor after an
> already existing one.
>
> Simplify this by never setting NDE unless when we actually chain a descriptor.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
With correction suggested by Vinod
Acked-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
> ---
> drivers/dma/at_xdmac.c | 41 ++++++++++++++++++++---------------------
> 1 file changed, 20 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index cbeadeeed9c0..67e566b2b24f 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -471,6 +471,20 @@ static struct at_xdmac_desc *at_xdmac_get_desc(struct at_xdmac_chan *atchan)
> return desc;
> }
>
> +static void at_xdmac_queue_desc(struct dma_chan *chan,
> + struct at_xdmac_desc *prev,
> + struct at_xdmac_desc *desc)
> +{
> + if (!prev || !desc)
> + return;
> +
> + prev->lld.mbr_nda = desc->tx_dma_desc.phys;
> + prev->lld.mbr_ubc |= AT_XDMAC_MBR_UBC_NDE;
> +
> + dev_dbg(chan2dev(chan), "%s: chain lld: prev=0x%p, mbr_nda=0x%08x\n",
> + __func__, prev, prev->lld.mbr_nda);
> +}
> +
> static struct dma_chan *at_xdmac_xlate(struct of_phandle_args *dma_spec,
> struct of_dma *of_dma)
> {
> @@ -627,19 +641,14 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> desc->lld.mbr_ubc = AT_XDMAC_MBR_UBC_NDV2 /* next descriptor view */
> | AT_XDMAC_MBR_UBC_NDEN /* next descriptor dst parameter update */
> | AT_XDMAC_MBR_UBC_NSEN /* next descriptor src parameter update */
> - | (i == sg_len - 1 ? 0 : AT_XDMAC_MBR_UBC_NDE) /* descriptor fetch */
> | (len >> fixed_dwidth); /* microblock length */
> dev_dbg(chan2dev(chan),
> "%s: lld: mbr_sa=%pad, mbr_da=%pad, mbr_ubc=0x%08x\n",
> __func__, &desc->lld.mbr_sa, &desc->lld.mbr_da, desc->lld.mbr_ubc);
>
> /* Chain lld. */
> - if (prev) {
> - prev->lld.mbr_nda = desc->tx_dma_desc.phys;
> - dev_dbg(chan2dev(chan),
> - "%s: chain lld: prev=0x%p, mbr_nda=%pad\n",
> - __func__, prev, &prev->lld.mbr_nda);
> - }
> + if (prev)
> + at_xdmac_queue_desc(chan, prev, desc);
>
> prev = desc;
> if (!first)
> @@ -714,7 +723,6 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
> desc->lld.mbr_ubc = AT_XDMAC_MBR_UBC_NDV1
> | AT_XDMAC_MBR_UBC_NDEN
> | AT_XDMAC_MBR_UBC_NSEN
> - | AT_XDMAC_MBR_UBC_NDE
> | period_len >> at_xdmac_get_dwidth(desc->lld.mbr_cfg);
>
> dev_dbg(chan2dev(chan),
> @@ -722,12 +730,8 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
> __func__, &desc->lld.mbr_sa, &desc->lld.mbr_da, desc->lld.mbr_ubc);
>
> /* Chain lld. */
> - if (prev) {
> - prev->lld.mbr_nda = desc->tx_dma_desc.phys;
> - dev_dbg(chan2dev(chan),
> - "%s: chain lld: prev=0x%p, mbr_nda=%pad\n",
> - __func__, prev, &prev->lld.mbr_nda);
> - }
> + if (prev)
> + at_xdmac_queue_desc(chan, prev, desc);
>
> prev = desc;
> if (!first)
> @@ -850,7 +854,6 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
> desc->lld.mbr_ubc = AT_XDMAC_MBR_UBC_NDV2
> | AT_XDMAC_MBR_UBC_NDEN
> | AT_XDMAC_MBR_UBC_NSEN
> - | (remaining_size ? AT_XDMAC_MBR_UBC_NDE : 0)
> | ublen;
> desc->lld.mbr_cfg = chan_cc;
>
> @@ -859,12 +862,8 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
> __func__, &desc->lld.mbr_sa, &desc->lld.mbr_da, desc->lld.mbr_ubc, desc->lld.mbr_cfg);
>
> /* Chain lld. */
> - if (prev) {
> - prev->lld.mbr_nda = desc->tx_dma_desc.phys;
> - dev_dbg(chan2dev(chan),
> - "%s: chain lld: prev=0x%p, mbr_nda=0x%08x\n",
> - __func__, prev, prev->lld.mbr_nda);
> - }
> + if (prev)
> + at_xdmac_queue_desc(chan, prev, desc);
>
> prev = desc;
> if (!first)
> --
> 2.3.6
>
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