[PATCH 2/2] dmaengine: xdmac: Add scatter gathered memset support
Maxime Ripard
maxime.ripard at free-electrons.com
Mon Jul 6 03:19:24 PDT 2015
The XDMAC also supports memset operations over discontiguous areas. Add the
necessary logic to support this.
Signed-off-by: Maxime Ripard <maxime.ripard at 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.
+ */
+ 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;
--
2.4.5
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