dmaengine: xdmac: Add scatter gathered memset support

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>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index cf1213d..1a2d9a3 100644 (file)
--- 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;