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Subject[PATCH 2/2] dma: at_hdmac: Add support for memory to memory sg transfers
Date
From: Torsten Fleischer <torfl6749@gmail.com>

This patch adds support for memory to memory scatter-gather transfers.

Signed-off-by: Torsten Fleischer <torfl6749@gmail.com>
---
drivers/dma/at_hdmac.c | 165 +++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 154 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 0fb98a3..4d2dff6 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -60,6 +60,21 @@ static void atc_issue_pending(struct dma_chan *chan);

/*----------------------------------------------------------------------*/

+static inline unsigned int atc_get_xfer_width(dma_addr_t src, dma_addr_t dst,
+ size_t len)
+{
+ unsigned int width;
+
+ if (!((src | dst | len) & 3))
+ width = 2;
+ else if (!((src | dst | len) & 1))
+ width = 1;
+ else
+ width = 0;
+
+ return width;
+}
+
static struct at_desc *atc_first_active(struct at_dma_chan *atchan)
{
return list_first_entry(&atchan->active_list,
@@ -620,16 +635,10 @@ atc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
* We can be a lot more clever here, but this should take care
* of the most common optimization.
*/
- if (!((src | dest | len) & 3)) {
- ctrla = ATC_SRC_WIDTH_WORD | ATC_DST_WIDTH_WORD;
- src_width = dst_width = 2;
- } else if (!((src | dest | len) & 1)) {
- ctrla = ATC_SRC_WIDTH_HALFWORD | ATC_DST_WIDTH_HALFWORD;
- src_width = dst_width = 1;
- } else {
- ctrla = ATC_SRC_WIDTH_BYTE | ATC_DST_WIDTH_BYTE;
- src_width = dst_width = 0;
- }
+ src_width = dst_width = atc_get_xfer_width(src, dest, len);
+
+ ctrla = ATC_SRC_WIDTH(src_width) |
+ ATC_DST_WIDTH(dst_width);

for (offset = 0; offset < len; offset += xfer_count << src_width) {
xfer_count = min_t(size_t, (len - offset) >> src_width,
@@ -815,6 +824,134 @@ err:
}

/**
+ * atc_prep_dma_sg - prepare memory to memory scather-gather operation
+ * @chan: the channel to prepare operation on
+ * @dst_sg: destination scatterlist
+ * @dst_nents: number of destination scatterlist entries
+ * @src_sg: source scatterlist
+ * @src_nents: number of source scatterlist entries
+ * @flags: tx descriptor status flags
+ */
+static struct dma_async_tx_descriptor *
+atc_prep_dma_sg(struct dma_chan *chan,
+ struct scatterlist *dst_sg, unsigned int dst_nents,
+ struct scatterlist *src_sg, unsigned int src_nents,
+ unsigned long flags)
+{
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ struct at_desc *desc = NULL;
+ struct at_desc *first = NULL;
+ struct at_desc *prev = NULL;
+ unsigned int src_width;
+ unsigned int dst_width;
+ size_t xfer_count;
+ u32 ctrla;
+ u32 ctrlb;
+ size_t dst_len = 0, src_len = 0;
+ dma_addr_t dst = 0, src = 0;
+ size_t len = 0, total_len = 0;
+
+ if (unlikely(dst_nents == 0 || src_nents == 0))
+ return NULL;
+
+ if (unlikely(dst_sg == NULL || src_sg == NULL))
+ return NULL;
+
+ ctrlb = ATC_DEFAULT_CTRLB | ATC_IEN
+ | ATC_SRC_ADDR_MODE_INCR
+ | ATC_DST_ADDR_MODE_INCR
+ | ATC_FC_MEM2MEM;
+
+ /* loop until there is either no more source or no more destination
+ * scatterlist entry */
+ while (true) {
+
+ /* prepare the next transfer */
+ if (dst_len == 0) {
+
+ /* no more destination scatterlist entries */
+ if (!dst_sg || !dst_nents)
+ break;
+
+ dst = sg_dma_address(dst_sg);
+ dst_len = sg_dma_len(dst_sg);
+
+ dst_sg = sg_next(dst_sg);
+ dst_nents--;
+ }
+
+ if (src_len == 0) {
+
+ /* no more source scatterlist entries */
+ if (!src_sg || !src_nents)
+ break;
+
+ src = sg_dma_address(src_sg);
+ src_len = sg_dma_len(src_sg);
+
+ src_sg = sg_next(src_sg);
+ src_nents--;
+ }
+
+ len = min_t(size_t, src_len, dst_len);
+ if (len == 0)
+ continue;
+
+ /* take care for the alignment */
+ src_width = dst_width = atc_get_xfer_width(src, dst, len);
+
+ ctrla = ATC_SRC_WIDTH(src_width) |
+ ATC_DST_WIDTH(dst_width);
+
+ /* The number of transfers to set up refer to the source width
+ * that depends on the alignment. */
+ xfer_count = len >> src_width;
+ if (xfer_count > ATC_BTSIZE_MAX) {
+ xfer_count = ATC_BTSIZE_MAX;
+ len = ATC_BTSIZE_MAX << src_width;
+ }
+
+ /* create the transfer */
+ desc = atc_desc_get(atchan);
+ if (!desc)
+ goto err_desc_get;
+
+ desc->lli.saddr = src;
+ desc->lli.daddr = dst;
+ desc->lli.ctrla = ctrla | xfer_count;
+ desc->lli.ctrlb = ctrlb;
+
+ desc->txd.cookie = 0;
+ desc->len = len;
+
+ atc_desc_chain(&first, &prev, desc);
+
+ /* update the lengths and addresses for the next loop cycle */
+ dst_len -= len;
+ src_len -= len;
+ dst += len;
+ src += len;
+
+ total_len += len;
+ }
+
+ /* First descriptor of the chain embedds additional information */
+ first->txd.cookie = -EBUSY;
+ first->total_len = total_len;
+
+ /* set end-of-link to the last link descriptor of list*/
+ set_desc_eol(desc);
+
+ first->txd.flags = flags; /* client is in control of this ack */
+
+ return &first->txd;
+
+err_desc_get:
+ atc_desc_put(atchan, first);
+ return NULL;
+}
+
+/**
* atc_dma_cyclic_check_values
* Check for too big/unaligned periods and unaligned DMA buffer
*/
@@ -1391,8 +1528,10 @@ static int __init at_dma_probe(struct platform_device *pdev)

/* setup platform data for each SoC */
dma_cap_set(DMA_MEMCPY, at91sam9rl_config.cap_mask);
+ dma_cap_set(DMA_SG, at91sam9rl_config.cap_mask);
dma_cap_set(DMA_MEMCPY, at91sam9g45_config.cap_mask);
dma_cap_set(DMA_SLAVE, at91sam9g45_config.cap_mask);
+ dma_cap_set(DMA_SG, at91sam9g45_config.cap_mask);

/* get DMA parameters from controller type */
plat_dat = at_dma_get_driver_data(pdev);
@@ -1505,11 +1644,15 @@ static int __init at_dma_probe(struct platform_device *pdev)
atdma->dma_common.device_control = atc_control;
}

+ if (dma_has_cap(DMA_SG, atdma->dma_common.cap_mask))
+ atdma->dma_common.device_prep_dma_sg = atc_prep_dma_sg;
+
dma_writel(atdma, EN, AT_DMA_ENABLE);

- dev_info(&pdev->dev, "Atmel AHB DMA Controller ( %s%s), %d channels\n",
+ dev_info(&pdev->dev, "Atmel AHB DMA Controller ( %s%s%s), %d channels\n",
dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask) ? "cpy " : "",
dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask) ? "slave " : "",
+ dma_has_cap(DMA_SG, atdma->dma_common.cap_mask) ? "sg-cpy " : "",
plat_dat->nr_channels);

dma_async_device_register(&atdma->dma_common);
--
2.1.4


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