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Subject[PATCH v5 16/16] dmaengine: dw-axi-dmac: Virtually split the linked-list
Date
AxiDMA driver exposed the dma_set_max_seg_size() to the DMAENGINE.
It shall helps the DMA clients to create size-optimized linked-list
for the controller.

However, there are certain situations where DMA client might not be
abled to benefit from the dma_get_max_seg_size() if the segment size
can't meet the nature of the DMA client's operation.

In the case of ALSA operation, ALSA application and driver expecting
to run in a period of larger than 10ms regardless of the bit depth.
With this large period, there is a strong request to split the linked-list
in the AxiDMA driver.

Signed-off-by: Sia Jee Heng <jee.heng.sia@intel.com>
---
.../dma/dw-axi-dmac/dw-axi-dmac-platform.c | 111 ++++++++++++++----
drivers/dma/dw-axi-dmac/dw-axi-dmac.h | 1 +
2 files changed, 92 insertions(+), 20 deletions(-)

diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
index 1a218fcdbb16..cfa7256f207d 100644
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
@@ -576,6 +576,11 @@ static int dw_axi_dma_set_hw_desc(struct axi_dma_chan *chan,
if (mem_width > DWAXIDMAC_TRANS_WIDTH_32)
mem_width = DWAXIDMAC_TRANS_WIDTH_32;

+ if (!IS_ALIGNED(mem_addr, 4)) {
+ dev_err(chan->chip->dev, "invalid buffer alignment\n");
+ return -EINVAL;
+ }
+
switch (chan->direction) {
case DMA_MEM_TO_DEV:
reg_width = __ffs(chan->config.dst_addr_width);
@@ -637,6 +642,35 @@ static int dw_axi_dma_set_hw_desc(struct axi_dma_chan *chan,
return 0;
}

+static size_t calculate_block_len(struct axi_dma_chan *chan,
+ dma_addr_t dma_addr, size_t buf_len,
+ enum dma_transfer_direction direction)
+{
+ u32 data_width, reg_width, mem_width;
+ size_t axi_block_ts, block_len;
+
+ axi_block_ts = chan->chip->dw->hdata->block_size[chan->id];
+
+ switch (direction) {
+ case DMA_MEM_TO_DEV:
+ data_width = BIT(chan->chip->dw->hdata->m_data_width);
+ mem_width = __ffs(data_width | dma_addr | buf_len);
+ if (mem_width > DWAXIDMAC_TRANS_WIDTH_32)
+ mem_width = DWAXIDMAC_TRANS_WIDTH_32;
+
+ block_len = axi_block_ts << mem_width;
+ break;
+ case DMA_DEV_TO_MEM:
+ reg_width = __ffs(chan->config.src_addr_width);
+ block_len = axi_block_ts << reg_width;
+ break;
+ default:
+ block_len = 0;
+ }
+
+ return block_len;
+}
+
static struct dma_async_tx_descriptor *
dw_axi_dma_chan_prep_cyclic(struct dma_chan *dchan, dma_addr_t dma_addr,
size_t buf_len, size_t period_len,
@@ -647,13 +681,27 @@ dw_axi_dma_chan_prep_cyclic(struct dma_chan *dchan, dma_addr_t dma_addr,
struct axi_dma_hw_desc *hw_desc = NULL;
struct axi_dma_desc *desc = NULL;
dma_addr_t src_addr = dma_addr;
- u32 num_periods = buf_len / period_len;
+ u32 num_periods, num_segments;
+ size_t axi_block_len;
+ u32 total_segments;
+ u32 segment_len;
unsigned int i;
int status;
u64 llp = 0;
u8 lms = 0; /* Select AXI0 master for LLI fetching */

- desc = axi_desc_alloc(num_periods);
+ num_periods = buf_len / period_len;
+
+ axi_block_len = calculate_block_len(chan, dma_addr, buf_len, direction);
+ if (axi_block_len == 0)
+ return NULL;
+
+ num_segments = DIV_ROUND_UP(period_len, axi_block_len);
+ segment_len = DIV_ROUND_UP(period_len, num_segments);
+
+ total_segments = num_periods * num_segments;
+
+ desc = axi_desc_alloc(num_periods * num_segments);
if (unlikely(!desc))
goto err_desc_get;

@@ -661,12 +709,13 @@ dw_axi_dma_chan_prep_cyclic(struct dma_chan *dchan, dma_addr_t dma_addr,
desc->chan = chan;
chan->cyclic = true;
desc->length = 0;
+ desc->period_len = period_len;

- for (i = 0; i < num_periods; i++) {
+ for (i = 0; i < total_segments; i++) {
hw_desc = &desc->hw_desc[i];

status = dw_axi_dma_set_hw_desc(chan, hw_desc, src_addr,
- period_len);
+ segment_len);
if (status < 0)
goto err_desc_get;

@@ -676,17 +725,17 @@ dw_axi_dma_chan_prep_cyclic(struct dma_chan *dchan, dma_addr_t dma_addr,
*/
set_desc_last(hw_desc);

- src_addr += period_len;
+ src_addr += segment_len;
}

llp = desc->hw_desc[0].llp;

/* Managed transfer list */
do {
- hw_desc = &desc->hw_desc[--num_periods];
+ hw_desc = &desc->hw_desc[--total_segments];
write_desc_llp(hw_desc, llp | lms);
llp = hw_desc->llp;
- } while (num_periods);
+ } while (total_segments);

if (dw_axi_dma_set_hw_channel(chan->chip, chan->hw_handshake_num, true))
goto err_desc_get;
@@ -709,9 +758,13 @@ dw_axi_dma_chan_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
struct axi_dma_chan *chan = dchan_to_axi_dma_chan(dchan);
struct axi_dma_hw_desc *hw_desc = NULL;
struct axi_dma_desc *desc = NULL;
+ u32 num_segments, segment_len;
+ unsigned int loop = 0;
struct scatterlist *sg;
+ size_t axi_block_len;
+ u32 len, num_sgs = 0;
unsigned int i;
- u32 mem, len;
+ dma_addr_t mem;
int status;
u64 llp = 0;
u8 lms = 0; /* Select AXI0 master for LLI fetching */
@@ -719,35 +772,51 @@ dw_axi_dma_chan_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
if (unlikely(!is_slave_direction(direction) || !sg_len))
return NULL;

- chan->direction = direction;
+ mem = sg_dma_address(sgl);
+ len = sg_dma_len(sgl);
+
+ axi_block_len = calculate_block_len(chan, mem, len, direction);
+ if (axi_block_len == 0)
+ return NULL;

- desc = axi_desc_alloc(sg_len);
+ for_each_sg(sgl, sg, sg_len, i)
+ num_sgs += DIV_ROUND_UP(sg_dma_len(sg), axi_block_len);
+
+ desc = axi_desc_alloc(num_sgs);
if (unlikely(!desc))
goto err_desc_get;

desc->chan = chan;
desc->length = 0;
+ chan->direction = direction;

for_each_sg(sgl, sg, sg_len, i) {
mem = sg_dma_address(sg);
len = sg_dma_len(sg);
- hw_desc = &desc->hw_desc[i];
-
- status = dw_axi_dma_set_hw_desc(chan, hw_desc, mem, len);
- if (status < 0)
- goto err_desc_get;
- desc->length += hw_desc->len;
+ num_segments = DIV_ROUND_UP(sg_dma_len(sg), axi_block_len);
+ segment_len = DIV_ROUND_UP(sg_dma_len(sg), num_segments);
+
+ do {
+ hw_desc = &desc->hw_desc[loop++];
+ status = dw_axi_dma_set_hw_desc(chan, hw_desc, mem, segment_len);
+ if (status < 0)
+ goto err_desc_get;
+
+ desc->length += hw_desc->len;
+ len -= segment_len;
+ mem += segment_len;
+ } while (len >= segment_len);
}

/* Set end-of-link to the last link descriptor of list */
- set_desc_last(&desc->hw_desc[sg_len - 1]);
+ set_desc_last(&desc->hw_desc[num_sgs - 1]);

/* Managed transfer list */
do {
- hw_desc = &desc->hw_desc[--sg_len];
+ hw_desc = &desc->hw_desc[--num_sgs];
write_desc_llp(hw_desc, llp | lms);
llp = hw_desc->llp;
- } while (sg_len);
+ } while (num_sgs);

if (dw_axi_dma_set_hw_channel(chan->chip, chan->hw_handshake_num, true))
goto err_desc_get;
@@ -950,7 +1019,6 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan)
vd = vchan_next_desc(&chan->vc);

if (chan->cyclic) {
- vchan_cyclic_callback(vd);
desc = vd_to_axi_desc(vd);
if (desc) {
llp = lo_hi_readq(chan->chan_regs + CH_LLP);
@@ -960,6 +1028,9 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan)
axi_chan_irq_clear(chan, hw_desc->lli->status_lo);
hw_desc->lli->ctl_hi |= CH_CTL_H_LLI_VALID;
desc->completed_blocks = i;
+
+ if (((hw_desc->len * (i + 1)) % desc->period_len) == 0)
+ vchan_cyclic_callback(vd);
break;
}
}
diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
index 1e937ea2a96d..b69897887c76 100644
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
@@ -100,6 +100,7 @@ struct axi_dma_desc {
struct axi_dma_chan *chan;
u32 completed_blocks;
u32 length;
+ u32 period_len;
};

static inline struct device *dchan2dev(struct dma_chan *dchan)
--
2.18.0
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