[PATCH 3/3] dmaengine: Add consumer for the new DMA_MEMCPY_SG API function.

Adrian Larumbe
2021-11-01T18:32:44Z

This new CDMA binding for device_prep_dma_memcpy_sg was partially borrowed
from xlnx kernel tree, an expanded with extended address space support when
linking descriptor segments and checking for incorrect zero transfer size.

Signed-off-by: Adrian Larumbe <adrianml@alumnos.upm.es>
---
drivers/dma/xilinx/xilinx_dma.c | 122 ++++++++++++++++++++++++++++++++
1 file changed, 122 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 4677ce08ed40..61618148f9d4 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -2127,6 +2127,126 @@ xilinx_cdma_prep_memcpy(struct dma_chan *dchan, dma_addr_t dma_dst,
return NULL;
}

+/**
+ * xilinx_cdma_prep_memcpy_sg - prepare descriptors for a memcpy_sg transaction
+ * @dchan: DMA channel
+ * @dst_sg: Destination scatter list
+ * @dst_sg_len: Number of entries in destination scatter list
+ * @src_sg: Source scatter list
+ * @src_sg_len: Number of entries in source scatter list
+ * @flags: transfer ack flags
+ *
+ * Return: Async transaction descriptor on success and NULL on failure
+ */
+static struct dma_async_tx_descriptor *xilinx_cdma_prep_memcpy_sg(
+ struct dma_chan *dchan, struct scatterlist *dst_sg,
+ unsigned int dst_sg_len, struct scatterlist *src_sg,
+ unsigned int src_sg_len, unsigned long flags)
+{
+ struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
+ struct xilinx_dma_tx_descriptor *desc;
+ struct xilinx_cdma_tx_segment *segment, *prev = NULL;
+ struct xilinx_cdma_desc_hw *hw;
+ size_t len, dst_avail, src_avail;
+ dma_addr_t dma_dst, dma_src;
+
+ if (unlikely(dst_sg_len == 0 || src_sg_len == 0))
+ return NULL;
+
+ if (unlikely(!dst_sg || !src_sg))
+ return NULL;
+
+ desc = xilinx_dma_alloc_tx_descriptor(chan);
+ if (!desc)
+ return NULL;
+
+ dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
+ desc->async_tx.tx_submit = xilinx_dma_tx_submit;
+
+ dst_avail = sg_dma_len(dst_sg);
+ src_avail = sg_dma_len(src_sg);
+ /*
+ * loop until there is either no more source or no more destination
+ * scatterlist entry
+ */
+ while (true) {
+ len = min_t(size_t, src_avail, dst_avail);
+ len = min_t(size_t, len, chan->xdev->max_buffer_len);
+ if (len == 0)
+ goto fetch;
+
+ /* Allocate the link descriptor from DMA pool */
+ segment = xilinx_cdma_alloc_tx_segment(chan);
+ if (!segment)
+ goto error;
+
+ dma_dst = sg_dma_address(dst_sg) + sg_dma_len(dst_sg) -
+ dst_avail;
+ dma_src = sg_dma_address(src_sg) + sg_dma_len(src_sg) -
+ src_avail;
+ hw = &segment->hw;
+ hw->control = len;
+ hw->src_addr = dma_src;
+ hw->dest_addr = dma_dst;
+ if (chan->ext_addr) {
+ hw->src_addr_msb = upper_32_bits(dma_src);
+ hw->dest_addr_msb = upper_32_bits(dma_dst);
+ }
+
+ if (prev) {
+ prev->hw.next_desc = segment->phys;
+ if (chan->ext_addr)
+ prev->hw.next_desc_msb =
+ upper_32_bits(segment->phys);
+ }
+
+ prev = segment;
+ dst_avail -= len;
+ src_avail -= len;
+ list_add_tail(&segment->node, &desc->segments);
+
+fetch:
+ /* Fetch the next dst scatterlist entry */
+ if (dst_avail == 0) {
+ if (dst_sg_len == 0)
+ break;
+ dst_sg = sg_next(dst_sg);
+ if (dst_sg == NULL)
+ break;
+ dst_sg_len--;
+ dst_avail = sg_dma_len(dst_sg);
+ }
+ /* Fetch the next src scatterlist entry */
+ if (src_avail == 0) {
+ if (src_sg_len == 0)
+ break;
+ src_sg = sg_next(src_sg);
+ if (src_sg == NULL)
+ break;
+ src_sg_len--;
+ src_avail = sg_dma_len(src_sg);
+ }
+ }
+
+ if (list_empty(&desc->segments)) {
+ dev_err(chan->xdev->dev,
+ "%s: Zero-size SG transfer requested\n", __func__);
+ goto error;
+ }
+
+ /* Link the last hardware descriptor with the first. */
+ segment = list_first_entry(&desc->segments,
+ struct xilinx_cdma_tx_segment, node);
+ desc->async_tx.phys = segment->phys;
+ prev->hw.next_desc = segment->phys;
+
+ return &desc->async_tx;
+
+error:
+ xilinx_dma_free_tx_descriptor(chan, desc);
+ return NULL;
+}
+
/**
* xilinx_dma_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
* @dchan: DMA channel
@@ -3115,7 +3235,9 @@ static int xilinx_dma_probe(struct platform_device *pdev)
DMA_RESIDUE_GRANULARITY_SEGMENT;
} else if (xdev->dma_config->dmatype == XDMA_TYPE_CDMA) {
dma_cap_set(DMA_MEMCPY, xdev->common.cap_mask);
+ dma_cap_set(DMA_MEMCPY_SG, xdev->common.cap_mask);
xdev->common.device_prep_dma_memcpy = xilinx_cdma_prep_memcpy;
+ xdev->common.device_prep_dma_memcpy_sg = xilinx_cdma_prep_memcpy_sg;
/* Residue calculation is supported by only AXI DMA and CDMA */
xdev->common.residue_granularity =
DMA_RESIDUE_GRANULARITY_SEGMENT;
--
2.33.1