| Message ID | 1436177964-19380-3-git-send-email-maxime.ripard@free-electrons.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Mon, Jul 06, 2015 at 12:19:24PM +0200, Maxime Ripard wrote: > The XDMAC also supports memset operations over discontiguous areas. Add the > necessary logic to support this. > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> > --- > drivers/dma/at_xdmac.c | 166 ++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 165 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c > index cf1213de7865..1a2d9a39ff25 100644 > --- a/drivers/dma/at_xdmac.c > +++ b/drivers/dma/at_xdmac.c > @@ -1133,7 +1133,7 @@ static struct at_xdmac_desc *at_xdmac_memset_create_desc(struct dma_chan *chan, > * SAMA5D4x), so we can use the same interface for source and dest, > * that solves the fact we don't know the direction. > */ > - u32 chan_cc = AT_XDMAC_CC_DAM_INCREMENTED_AM > + u32 chan_cc = AT_XDMAC_CC_DAM_UBS_AM > | AT_XDMAC_CC_SAM_INCREMENTED_AM > | AT_XDMAC_CC_DIF(0) > | AT_XDMAC_CC_SIF(0) > @@ -1201,6 +1201,168 @@ at_xdmac_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value, > return &desc->tx_dma_desc; > } > > +static struct dma_async_tx_descriptor * > +at_xdmac_prep_dma_memset_sg(struct dma_chan *chan, struct scatterlist *sgl, > + unsigned int sg_len, int value, > + unsigned long flags) > +{ > + struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan); > + struct at_xdmac_desc *desc, *pdesc = NULL, > + *ppdesc = NULL, *first = NULL; > + struct scatterlist *sg, *psg = NULL, *ppsg = NULL; > + size_t stride = 0, pstride = 0, len = 0; > + int i; > + > + if (!sgl) > + return NULL; > + > + dev_dbg(chan2dev(chan), "%s: sg_len=%d, value=0x%x, flags=0x%lx\n", > + __func__, sg_len, value, flags); > + > + /* Prepare descriptors. */ > + for_each_sg(sgl, sg, sg_len, i) { > + dev_dbg(chan2dev(chan), "%s: dest=0x%08x, len=%d, pattern=0x%x, flags=0x%lx\n", > + __func__, sg_dma_address(sg), sg_dma_len(sg), > + value, flags); > + desc = at_xdmac_memset_create_desc(chan, atchan, > + sg_dma_address(sg), > + sg_dma_len(sg), > + value); > + if (!desc && first) > + list_splice_init(&first->descs_list, > + &atchan->free_descs_list); > + > + if (!first) > + first = desc; > + > + /* Update our strides */ > + pstride = stride; > + if (psg) > + stride = sg_dma_address(sg) - > + (sg_dma_address(psg) + sg_dma_len(psg)); > + > + /* > + * The scatterlist API gives us only the address and > + * length of each elements. > + * > + * Unfortunately, we don't have the stride, which we > + * will need to compute. > + * > + * That make us end up in a situation like this one: > + * len stride len stride len > + * +-------+ +-------+ +-------+ > + * | N-2 | | N-1 | | N | > + * +-------+ +-------+ +-------+ > + * > + * We need all these three elements (N-2, N-1 and N) > + * to actually take the decision on whether we need to > + * queue N-1 or reuse N-2. > + * > + * We will only consider N if it is the last element. > + */ Why do you need stride? This is scatterlist so the computation of stride sounds odd here. Ideally you should take the scatterlist and program the lli for controller.
Hi Vinod, > > + /* > > + * The scatterlist API gives us only the address and > > + * length of each elements. > > + * > > + * Unfortunately, we don't have the stride, which we > > + * will need to compute. > > + * > > + * That make us end up in a situation like this one: > > + * len stride len stride len > > + * +-------+ +-------+ +-------+ > > + * | N-2 | | N-1 | | N | > > + * +-------+ +-------+ +-------+ > > + * > > + * We need all these three elements (N-2, N-1 and N) > > + * to actually take the decision on whether we need to > > + * queue N-1 or reuse N-2. > > + * > > + * We will only consider N if it is the last element. > > + */ > > Why do you need stride? > > This is scatterlist so the computation of stride sounds odd here. Ideally > you should take the scatterlist and program the lli for controller. Because it is sub-optimal if the length and stride are equals from one descriptors to another. The XDMAC is able to repeat any given descriptor a given number of time (which is one by default), which means that if the parameters of the transfer don't change, we simply have to increment the number of time the descriptor has to be used, instead of creating a new one that the controller will have to fetch. In the non-optimal case (ie the length and/or stride change from one scatterlist element to another), we simply fallback to a one LLI per scatter list element. Maxime
On Thu, Jul 16, 2015 at 04:11:05PM +0200, Maxime Ripard wrote: > Hi Vinod, > > > > + /* > > > + * The scatterlist API gives us only the address and > > > + * length of each elements. > > > + * > > > + * Unfortunately, we don't have the stride, which we > > > + * will need to compute. > > > + * > > > + * That make us end up in a situation like this one: > > > + * len stride len stride len > > > + * +-------+ +-------+ +-------+ > > > + * | N-2 | | N-1 | | N | > > > + * +-------+ +-------+ +-------+ > > > + * > > > + * We need all these three elements (N-2, N-1 and N) > > > + * to actually take the decision on whether we need to > > > + * queue N-1 or reuse N-2. > > > + * > > > + * We will only consider N if it is the last element. > > > + */ > > > > Why do you need stride? > > > > This is scatterlist so the computation of stride sounds odd here. Ideally > > you should take the scatterlist and program the lli for controller. > > Because it is sub-optimal if the length and stride are equals from one > descriptors to another. The XDMAC is able to repeat any given > descriptor a given number of time (which is one by default), which > means that if the parameters of the transfer don't change, we simply > have to increment the number of time the descriptor has to be used, > instead of creating a new one that the controller will have to fetch. > > In the non-optimal case (ie the length and/or stride change from one > scatterlist element to another), we simply fallback to a one LLI per > scatter list element. Sound fine to me. The optimization is a good one then... Another question though, do you expect stride to be linear for your cases, if so have you actually though about using interleaved API, for these cases
On Fri, Jul 17, 2015 at 08:39:26AM +0530, Vinod Koul wrote: > On Thu, Jul 16, 2015 at 04:11:05PM +0200, Maxime Ripard wrote: > > Hi Vinod, > > > > > > + /* > > > > + * The scatterlist API gives us only the address and > > > > + * length of each elements. > > > > + * > > > > + * Unfortunately, we don't have the stride, which we > > > > + * will need to compute. > > > > + * > > > > + * That make us end up in a situation like this one: > > > > + * len stride len stride len > > > > + * +-------+ +-------+ +-------+ > > > > + * | N-2 | | N-1 | | N | > > > > + * +-------+ +-------+ +-------+ > > > > + * > > > > + * We need all these three elements (N-2, N-1 and N) > > > > + * to actually take the decision on whether we need to > > > > + * queue N-1 or reuse N-2. > > > > + * > > > > + * We will only consider N if it is the last element. > > > > + */ > > > > > > Why do you need stride? > > > > > > This is scatterlist so the computation of stride sounds odd here. Ideally > > > you should take the scatterlist and program the lli for controller. > > > > Because it is sub-optimal if the length and stride are equals from one > > descriptors to another. The XDMAC is able to repeat any given > > descriptor a given number of time (which is one by default), which > > means that if the parameters of the transfer don't change, we simply > > have to increment the number of time the descriptor has to be used, > > instead of creating a new one that the controller will have to fetch. > > > > In the non-optimal case (ie the length and/or stride change from one > > scatterlist element to another), we simply fallback to a one LLI per > > scatter list element. > > Sound fine to me. The optimization is a good one then... > > Another question though, do you expect stride to be linear for your > cases, if so have you actually though about using interleaved API, > for these cases What do you mean by linear? I guess, at least from an API point of view, we should expect any stride and length. The scatter gather variants of the dmaengine API were already using scatterlist, and the interleaved template doesn't really fit our use case here, so I chose to use a scatterlist here, mostly for consistency. Maxime
diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c index cf1213de7865..1a2d9a39ff25 100644 --- a/drivers/dma/at_xdmac.c +++ b/drivers/dma/at_xdmac.c @@ -1133,7 +1133,7 @@ static struct at_xdmac_desc *at_xdmac_memset_create_desc(struct dma_chan *chan, * SAMA5D4x), so we can use the same interface for source and dest, * that solves the fact we don't know the direction. */ - u32 chan_cc = AT_XDMAC_CC_DAM_INCREMENTED_AM + u32 chan_cc = AT_XDMAC_CC_DAM_UBS_AM | AT_XDMAC_CC_SAM_INCREMENTED_AM | AT_XDMAC_CC_DIF(0) | AT_XDMAC_CC_SIF(0) @@ -1201,6 +1201,168 @@ at_xdmac_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value, return &desc->tx_dma_desc; } +static struct dma_async_tx_descriptor * +at_xdmac_prep_dma_memset_sg(struct dma_chan *chan, struct scatterlist *sgl, + unsigned int sg_len, int value, + unsigned long flags) +{ + struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan); + struct at_xdmac_desc *desc, *pdesc = NULL, + *ppdesc = NULL, *first = NULL; + struct scatterlist *sg, *psg = NULL, *ppsg = NULL; + size_t stride = 0, pstride = 0, len = 0; + int i; + + if (!sgl) + return NULL; + + dev_dbg(chan2dev(chan), "%s: sg_len=%d, value=0x%x, flags=0x%lx\n", + __func__, sg_len, value, flags); + + /* Prepare descriptors. */ + for_each_sg(sgl, sg, sg_len, i) { + dev_dbg(chan2dev(chan), "%s: dest=0x%08x, len=%d, pattern=0x%x, flags=0x%lx\n", + __func__, sg_dma_address(sg), sg_dma_len(sg), + value, flags); + desc = at_xdmac_memset_create_desc(chan, atchan, + sg_dma_address(sg), + sg_dma_len(sg), + value); + if (!desc && first) + list_splice_init(&first->descs_list, + &atchan->free_descs_list); + + if (!first) + first = desc; + + /* Update our strides */ + pstride = stride; + if (psg) + stride = sg_dma_address(sg) - + (sg_dma_address(psg) + sg_dma_len(psg)); + + /* + * The scatterlist API gives us only the address and + * length of each elements. + * + * Unfortunately, we don't have the stride, which we + * will need to compute. + * + * That make us end up in a situation like this one: + * len stride len stride len + * +-------+ +-------+ +-------+ + * | N-2 | | N-1 | | N | + * +-------+ +-------+ +-------+ + * + * We need all these three elements (N-2, N-1 and N) + * to actually take the decision on whether we need to + * queue N-1 or reuse N-2. + * + * We will only consider N if it is the last element. + */ + if (ppdesc && pdesc) { + if ((stride == pstride) && + (sg_dma_len(ppsg) == sg_dma_len(psg))) { + dev_dbg(chan2dev(chan), + "%s: desc 0x%p can be merged with desc 0x%p\n", + __func__, pdesc, ppdesc); + + /* + * Increment the block count of the + * N-2 descriptor + */ + at_xdmac_increment_block_count(chan, ppdesc); + ppdesc->lld.mbr_dus = stride; + + /* + * Put back the N-1 descriptor in the + * free descriptor list + */ + list_add_tail(&pdesc->desc_node, + &atchan->free_descs_list); + + /* + * Make our N-1 descriptor pointer + * point to the N-2 since they were + * actually merged. + */ + pdesc = ppdesc; + + /* + * Rule out the case where we don't have + * pstride computed yet (our second sg + * element) + * + * We also want to catch the case where there + * would be a negative stride, + */ + } else if (pstride || + sg_dma_address(sg) < sg_dma_address(psg)) { + /* + * Queue the N-1 descriptor after the + * N-2 + */ + at_xdmac_queue_desc(chan, ppdesc, pdesc); + + /* + * Add the N-1 descriptor to the list + * of the descriptors used for this + * transfer + */ + list_add_tail(&desc->desc_node, + &first->descs_list); + dev_dbg(chan2dev(chan), + "%s: add desc 0x%p to descs_list 0x%p\n", + __func__, desc, first); + } + } + + /* + * If we are the last element, just see if we have the + * same size than the previous element. + * + * If so, we can merge it with the previous descriptor + * since we don't care about the stride anymore. + */ + if ((i == (sg_len - 1)) && + sg_dma_len(ppsg) == sg_dma_len(psg)) { + dev_dbg(chan2dev(chan), + "%s: desc 0x%p can be merged with desc 0x%p\n", + __func__, desc, pdesc); + + /* + * Increment the block count of the N-1 + * descriptor + */ + at_xdmac_increment_block_count(chan, pdesc); + pdesc->lld.mbr_dus = stride; + + /* + * Put back the N descriptor in the free + * descriptor list + */ + list_add_tail(&desc->desc_node, + &atchan->free_descs_list); + } + + /* Update our descriptors */ + ppdesc = pdesc; + pdesc = desc; + + /* Update our scatter pointers */ + ppsg = psg; + psg = sg; + + len += sg_dma_len(sg); + } + + first->tx_dma_desc.cookie = -EBUSY; + first->tx_dma_desc.flags = flags; + first->xfer_size = len; + + return &first->tx_dma_desc; +} + static enum dma_status at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie, struct dma_tx_state *txstate) @@ -1734,6 +1896,7 @@ static int at_xdmac_probe(struct platform_device *pdev) dma_cap_set(DMA_INTERLEAVE, atxdmac->dma.cap_mask); dma_cap_set(DMA_MEMCPY, atxdmac->dma.cap_mask); dma_cap_set(DMA_MEMSET, atxdmac->dma.cap_mask); + dma_cap_set(DMA_MEMSET_SG, atxdmac->dma.cap_mask); dma_cap_set(DMA_SLAVE, atxdmac->dma.cap_mask); /* * Without DMA_PRIVATE the driver is not able to allocate more than @@ -1749,6 +1912,7 @@ static int at_xdmac_probe(struct platform_device *pdev) atxdmac->dma.device_prep_interleaved_dma = at_xdmac_prep_interleaved; atxdmac->dma.device_prep_dma_memcpy = at_xdmac_prep_dma_memcpy; atxdmac->dma.device_prep_dma_memset = at_xdmac_prep_dma_memset; + atxdmac->dma.device_prep_dma_memset_sg = at_xdmac_prep_dma_memset_sg; atxdmac->dma.device_prep_slave_sg = at_xdmac_prep_slave_sg; atxdmac->dma.device_config = at_xdmac_device_config; atxdmac->dma.device_pause = at_xdmac_device_pause;
The XDMAC also supports memset operations over discontiguous areas. Add the necessary logic to support this. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> --- drivers/dma/at_xdmac.c | 166 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 165 insertions(+), 1 deletion(-)