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Subject[PATCH 1/3] dma: edma: Split out PaRAM set calculations into its own function
Date
PaRAM set calculation is abstracted into its own function to
enable better reuse for other DMA cases such as cyclic. We adapt
the Slave SG case to use the new function.

This provides a much cleaner abstraction to the internals of the
PaRAM set. However, any PaRAM attributes that are not common to
all DMA types must be set separately such as setting of interrupts.
This function takes care of the most-common attributes.

Also added comments clarifying A-sync case calculations.

Signed-off-by: Joel Fernandes <joelf@ti.com>
---
drivers/dma/edma.c | 198 ++++++++++++++++++++++++++++++++++-------------------
1 file changed, 126 insertions(+), 72 deletions(-)

diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
index ff50ff4..725b00c 100644
--- a/drivers/dma/edma.c
+++ b/drivers/dma/edma.c
@@ -250,6 +250,117 @@ static int edma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
return ret;
}

+/*
+ * A PaRAM set configuration abstraction used by other modes
+ * @chan: Channel who's PaRAM set we're configuring
+ * @pset: PaRAM set to initialize and setup.
+ * @src_addr: Source address of the DMA
+ * @dst_addr: Destination address of the DMA
+ * @burst: In units of dev_width, how much to send
+ * @dev_width: How much is the dev_width
+ * @dma_length: Total length of the DMA transfer
+ * @direction: Direction of the transfer
+ */
+static int edma_config_pset(struct dma_chan *chan, struct edmacc_param *pset,
+ dma_addr_t src_addr, dma_addr_t dst_addr, u32 burst,
+ enum dma_slave_buswidth dev_width, unsigned int dma_length,
+ enum dma_transfer_direction direction)
+{
+ struct edma_chan *echan = to_edma_chan(chan);
+ struct device *dev = chan->device->dev;
+ int acnt, bcnt, ccnt, cidx;
+ int src_bidx, dst_bidx, src_cidx, dst_cidx;
+ int absync;
+
+ acnt = dev_width;
+ /*
+ * If the maxburst is equal to the fifo width, use
+ * A-synced transfers. This allows for large contiguous
+ * buffer transfers using only one PaRAM set.
+ */
+ if (burst == 1) {
+ /*
+ * For the A-sync case, bcnt and ccnt are the remainder
+ * and quotient respectively of the division of:
+ * (dma_length / acnt) by (SZ_64K -1). This is so
+ * that in case bcnt over flows, we have ccnt to use.
+ * Note: In A-sync tranfer only, bcntrld is used, but it
+ * only applies for sg_dma_len(sg) >= SZ_64K.
+ * In this case, the best way adopted is- bccnt for the
+ * first frame will be the remainder below. Then for
+ * every successive frame, bcnt will be SZ_64K-1. This
+ * is assured as bcntrld = 0xffff in end of function.
+ */
+ absync = false;
+ ccnt = dma_length / acnt / (SZ_64K - 1);
+ bcnt = dma_length / acnt - ccnt * (SZ_64K - 1);
+ /*
+ * If bcnt is non-zero, we have a remainder and hence an
+ * extra frame to transfer, so increment ccnt.
+ */
+ if (bcnt)
+ ccnt++;
+ else
+ bcnt = SZ_64K - 1;
+ cidx = acnt;
+ } else {
+ /*
+ * If maxburst is greater than the fifo address_width,
+ * use AB-synced transfers where A count is the fifo
+ * address_width and B count is the maxburst. In this
+ * case, we are limited to transfers of C count frames
+ * of (address_width * maxburst) where C count is limited
+ * to SZ_64K-1. This places an upper bound on the length
+ * of an SG segment that can be handled.
+ */
+ absync = true;
+ bcnt = burst;
+ ccnt = dma_length / (acnt * bcnt);
+ if (ccnt > (SZ_64K - 1)) {
+ dev_err(dev, "Exceeded max SG segment size\n");
+ return -EINVAL;
+ }
+ cidx = acnt * bcnt;
+ }
+
+ if (direction == DMA_MEM_TO_DEV) {
+ src_bidx = acnt;
+ src_cidx = cidx;
+ dst_bidx = 0;
+ dst_cidx = 0;
+ } else if (direction == DMA_DEV_TO_MEM) {
+ src_bidx = 0;
+ src_cidx = 0;
+ dst_bidx = acnt;
+ dst_cidx = cidx;
+ } else {
+ dev_err(dev, "%s: direction not implemented yet\n", __func__);
+ return -EINVAL;
+ }
+
+ pset->opt = EDMA_TCC(EDMA_CHAN_SLOT(echan->ch_num));
+ /* Configure A or AB synchronized transfers */
+ if (absync)
+ pset->opt |= SYNCDIM;
+
+ pset->src = src_addr;
+ pset->dst = dst_addr;
+
+ pset->src_dst_bidx = (dst_bidx << 16) | src_bidx;
+ pset->src_dst_cidx = (dst_cidx << 16) | src_cidx;
+
+ pset->a_b_cnt = bcnt << 16 | acnt;
+ pset->ccnt = ccnt;
+ /*
+ * Only time when (bcntrld) auto reload is required is for
+ * A-sync case, and in this case, a requirement of reload value
+ * of SZ_64K-1 only is assured. 'link' is initially set to NULL
+ * and then later will be populated by edma_execute.
+ */
+ pset->link_bcntrld = 0xffffffff;
+ return absync;
+}
+
static struct dma_async_tx_descriptor *edma_prep_slave_sg(
struct dma_chan *chan, struct scatterlist *sgl,
unsigned int sg_len, enum dma_transfer_direction direction,
@@ -258,23 +369,21 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
struct edma_chan *echan = to_edma_chan(chan);
struct device *dev = chan->device->dev;
struct edma_desc *edesc;
- dma_addr_t dev_addr;
+ dma_addr_t src_addr = 0, dst_addr = 0;
enum dma_slave_buswidth dev_width;
u32 burst;
struct scatterlist *sg;
- int acnt, bcnt, ccnt, src, dst, cidx;
- int src_bidx, dst_bidx, src_cidx, dst_cidx;
- int i, nslots;
+ int i, nslots, ret;

if (unlikely(!echan || !sgl || !sg_len))
return NULL;

if (direction == DMA_DEV_TO_MEM) {
- dev_addr = echan->cfg.src_addr;
+ src_addr = echan->cfg.src_addr;
dev_width = echan->cfg.src_addr_width;
burst = echan->cfg.src_maxburst;
} else if (direction == DMA_MEM_TO_DEV) {
- dev_addr = echan->cfg.dst_addr;
+ dst_addr = echan->cfg.dst_addr;
dev_width = echan->cfg.dst_addr_width;
burst = echan->cfg.dst_maxburst;
} else {
@@ -313,63 +422,19 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(

/* Configure PaRAM sets for each SG */
for_each_sg(sgl, sg, sg_len, i) {
+ /* Get address for each SG */
+ if (direction == DMA_DEV_TO_MEM)
+ dst_addr = sg_dma_address(sg);
+ else
+ src_addr = sg_dma_address(sg);

- acnt = dev_width;
-
- /*
- * If the maxburst is equal to the fifo width, use
- * A-synced transfers. This allows for large contiguous
- * buffer transfers using only one PaRAM set.
- */
- if (burst == 1) {
- edesc->absync = false;
- ccnt = sg_dma_len(sg) / acnt / (SZ_64K - 1);
- bcnt = sg_dma_len(sg) / acnt - ccnt * (SZ_64K - 1);
- if (bcnt)
- ccnt++;
- else
- bcnt = SZ_64K - 1;
- cidx = acnt;
- /*
- * If maxburst is greater than the fifo address_width,
- * use AB-synced transfers where A count is the fifo
- * address_width and B count is the maxburst. In this
- * case, we are limited to transfers of C count frames
- * of (address_width * maxburst) where C count is limited
- * to SZ_64K-1. This places an upper bound on the length
- * of an SG segment that can be handled.
- */
- } else {
- edesc->absync = true;
- bcnt = burst;
- ccnt = sg_dma_len(sg) / (acnt * bcnt);
- if (ccnt > (SZ_64K - 1)) {
- dev_err(dev, "Exceeded max SG segment size\n");
- return NULL;
- }
- cidx = acnt * bcnt;
- }
-
- if (direction == DMA_MEM_TO_DEV) {
- src = sg_dma_address(sg);
- dst = dev_addr;
- src_bidx = acnt;
- src_cidx = cidx;
- dst_bidx = 0;
- dst_cidx = 0;
- } else {
- src = dev_addr;
- dst = sg_dma_address(sg);
- src_bidx = 0;
- src_cidx = 0;
- dst_bidx = acnt;
- dst_cidx = cidx;
- }
+ ret = edma_config_pset(chan, &edesc->pset[i], src_addr,
+ dst_addr, burst, dev_width,
+ sg_dma_len(sg), direction);
+ if (ret < 0)
+ return NULL;

- edesc->pset[i].opt = EDMA_TCC(EDMA_CHAN_SLOT(echan->ch_num));
- /* Configure A or AB synchronized transfers */
- if (edesc->absync)
- edesc->pset[i].opt |= SYNCDIM;
+ edesc->absync = ret;

/* If this is the last in a current SG set of transactions,
enable interrupts so that next set is processed */
@@ -379,17 +444,6 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
/* If this is the last set, enable completion interrupt flag */
if (i == sg_len - 1)
edesc->pset[i].opt |= TCINTEN;
-
- edesc->pset[i].src = src;
- edesc->pset[i].dst = dst;
-
- edesc->pset[i].src_dst_bidx = (dst_bidx << 16) | src_bidx;
- edesc->pset[i].src_dst_cidx = (dst_cidx << 16) | src_cidx;
-
- edesc->pset[i].a_b_cnt = bcnt << 16 | acnt;
- edesc->pset[i].ccnt = ccnt;
- edesc->pset[i].link_bcntrld = 0xffffffff;
-
}

return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
--
1.8.1.2


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