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Subject[PATCH v3] dmaengine: pl330: flush before wait, and add dev burst support.
Date
Do DMAFLUSHP _before_ the first DMAWFP to ensure controller
and peripheral are in agreement about dma request state before first
transfer. Add support for burst transfers to/from peripherals. In the new
scheme, the controller does as many burst transfers as it can then
transfers the remaining dregs with either single transfers for
peripherals, or with a reduced size burst for memory-to-memory transfers.

Signed-off-by: Frank Mori Hess <fmh6jj@gmail.com>
Tested-by: Frank Mori Hess <fmh6jj@gmail.com>

I tested dma transfers to peripherals with designware serial port
(drivers/tty/serial/8250/8250_dw.c) and a GPIB interface
(https://github.com/fmhess/fmh_gpib_core). I tested memory-to-memory
transfers using the dmatest module.

v3 of this patch should be the same as v2 except with checkpatch.pl
warnings and errors cleaned up.

---
drivers/dma/pl330.c | 146 +++++++++++++++++++++++++++++++++++++---------------
1 file changed, 104 insertions(+), 42 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index d7327fd5f445..cc2e4456bec1 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -1094,26 +1094,33 @@ static inline int _ldst_memtomem(unsigned dry_run, u8 buf[],
return off;
}

-static inline int _ldst_devtomem(struct pl330_dmac *pl330, unsigned dry_run,
- u8 buf[], const struct _xfer_spec *pxs,
- int cyc)
+static inline int _ldst_devtomem(struct pl330_dmac *pl330,
+ unsigned int dry_run, u8 buf[],
+ const struct _xfer_spec *pxs,
+ int cyc, enum pl330_cond cond)
{
int off = 0;
- enum pl330_cond cond;

if (pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
cond = BURST;
- else
- cond = SINGLE;

+ /* do FLUSHP at beginning to clear any stale dma requests before the
+ * first WFP.
+ */
+ if (!(pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP))
+ off += _emit_FLUSHP(dry_run, &buf[off], pxs->desc->peri);
while (cyc--) {
off += _emit_WFP(dry_run, &buf[off], cond, pxs->desc->peri);
- off += _emit_LDP(dry_run, &buf[off], cond, pxs->desc->peri);
+ if (cond == ALWAYS) {
+ off += _emit_LDP(dry_run, &buf[off], SINGLE,
+ pxs->desc->peri);
+ off += _emit_LDP(dry_run, &buf[off], BURST,
+ pxs->desc->peri);
+ } else {
+ off += _emit_LDP(dry_run, &buf[off], cond,
+ pxs->desc->peri);
+ }
off += _emit_ST(dry_run, &buf[off], ALWAYS);
-
- if (!(pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP))
- off += _emit_FLUSHP(dry_run, &buf[off],
- pxs->desc->peri);
}

return off;
@@ -1121,24 +1128,31 @@ static inline int _ldst_devtomem(struct pl330_dmac *pl330, unsigned dry_run,

static inline int _ldst_memtodev(struct pl330_dmac *pl330,
unsigned dry_run, u8 buf[],
- const struct _xfer_spec *pxs, int cyc)
+ const struct _xfer_spec *pxs, int cyc,
+ enum pl330_cond cond)
{
int off = 0;
- enum pl330_cond cond;

if (pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
cond = BURST;
- else
- cond = SINGLE;

+ /* do FLUSHP at beginning to clear any stale dma requests before the
+ * first WFP.
+ */
+ if (!(pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP))
+ off += _emit_FLUSHP(dry_run, &buf[off], pxs->desc->peri);
while (cyc--) {
off += _emit_WFP(dry_run, &buf[off], cond, pxs->desc->peri);
off += _emit_LD(dry_run, &buf[off], ALWAYS);
- off += _emit_STP(dry_run, &buf[off], cond, pxs->desc->peri);
-
- if (!(pl330->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP))
- off += _emit_FLUSHP(dry_run, &buf[off],
- pxs->desc->peri);
+ if (cond == ALWAYS) {
+ off += _emit_STP(dry_run, &buf[off], SINGLE,
+ pxs->desc->peri);
+ off += _emit_STP(dry_run, &buf[off], BURST,
+ pxs->desc->peri);
+ } else {
+ off += _emit_STP(dry_run, &buf[off], cond,
+ pxs->desc->peri);
+ }
}

return off;
@@ -1148,13 +1162,16 @@ static int _bursts(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
const struct _xfer_spec *pxs, int cyc)
{
int off = 0;
+ enum pl330_cond cond = BRST_LEN(pxs->ccr) > 1 ? BURST : SINGLE;

switch (pxs->desc->rqtype) {
case DMA_MEM_TO_DEV:
- off += _ldst_memtodev(pl330, dry_run, &buf[off], pxs, cyc);
+ off += _ldst_memtodev(pl330, dry_run, &buf[off], pxs, cyc,
+ cond);
break;
case DMA_DEV_TO_MEM:
- off += _ldst_devtomem(pl330, dry_run, &buf[off], pxs, cyc);
+ off += _ldst_devtomem(pl330, dry_run, &buf[off], pxs, cyc,
+ cond);
break;
case DMA_MEM_TO_MEM:
off += _ldst_memtomem(dry_run, &buf[off], pxs, cyc);
@@ -1167,6 +1184,46 @@ static int _bursts(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
return off;
}

+/* transfer dregs with single transfers to peripheral, or a reduced size burst
+ * for mem-to-mem.
+ */
+static int _dregs(struct pl330_dmac *pl330, unsigned int dry_run, u8 buf[],
+ const struct _xfer_spec *pxs, int transfer_length)
+{
+ int off = 0;
+ int dregs_ccr;
+
+ if (transfer_length == 0)
+ return off;
+
+ switch (pxs->desc->rqtype) {
+ case DMA_MEM_TO_DEV:
+ off += _ldst_memtodev(pl330, dry_run, &buf[off], pxs,
+ transfer_length, SINGLE);
+ break;
+ case DMA_DEV_TO_MEM:
+ off += _ldst_devtomem(pl330, dry_run, &buf[off], pxs,
+ transfer_length, SINGLE);
+ break;
+ case DMA_MEM_TO_MEM:
+ dregs_ccr = pxs->ccr;
+ dregs_ccr &= ~((0xf << CC_SRCBRSTLEN_SHFT) |
+ (0xf << CC_DSTBRSTLEN_SHFT));
+ dregs_ccr |= (((transfer_length - 1) & 0xf) <<
+ CC_SRCBRSTLEN_SHFT);
+ dregs_ccr |= (((transfer_length - 1) & 0xf) <<
+ CC_DSTBRSTLEN_SHFT);
+ off += _emit_MOV(dry_run, &buf[off], CCR, dregs_ccr);
+ off += _ldst_memtomem(dry_run, &buf[off], pxs, 1);
+ break;
+ default:
+ off += 0x40000000; /* Scare off the Client */
+ break;
+ }
+
+ return off;
+}
+
/* Returns bytes consumed and updates bursts */
static inline int _loop(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
unsigned long *bursts, const struct _xfer_spec *pxs)
@@ -1256,6 +1313,8 @@ static inline int _setup_loops(struct pl330_dmac *pl330,
struct pl330_xfer *x = &pxs->desc->px;
u32 ccr = pxs->ccr;
unsigned long c, bursts = BYTE_TO_BURST(x->bytes, ccr);
+ int num_dregs = (x->bytes - BURST_TO_BYTE(bursts, ccr)) /
+ BRST_SIZE(ccr);
int off = 0;

while (bursts) {
@@ -1263,6 +1322,7 @@ static inline int _setup_loops(struct pl330_dmac *pl330,
off += _loop(pl330, dry_run, &buf[off], &c, pxs);
bursts -= c;
}
+ off += _dregs(pl330, dry_run, &buf[off], pxs, num_dregs);

return off;
}
@@ -1294,7 +1354,6 @@ static int _setup_req(struct pl330_dmac *pl330, unsigned dry_run,
struct _xfer_spec *pxs)
{
struct _pl330_req *req = &thrd->req[index];
- struct pl330_xfer *x;
u8 *buf = req->mc_cpu;
int off = 0;

@@ -1303,11 +1362,6 @@ static int _setup_req(struct pl330_dmac *pl330, unsigned dry_run,
/* DMAMOV CCR, ccr */
off += _emit_MOV(dry_run, &buf[off], CCR, pxs->ccr);

- x = &pxs->desc->px;
- /* Error if xfer length is not aligned at burst size */
- if (x->bytes % (BRST_SIZE(pxs->ccr) * BRST_LEN(pxs->ccr)))
- return -EINVAL;
-
off += _setup_xfer(pl330, dry_run, &buf[off], pxs);

/* DMASEV peripheral/event */
@@ -2115,15 +2169,29 @@ static int pl330_config(struct dma_chan *chan,
pch->fifo_addr = slave_config->dst_addr;
if (slave_config->dst_addr_width)
pch->burst_sz = __ffs(slave_config->dst_addr_width);
- if (slave_config->dst_maxburst)
- pch->burst_len = slave_config->dst_maxburst;
+ if (pch->dmac->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
+ pch->burst_len = 1;
+ else if (slave_config->dst_maxburst) {
+ if (slave_config->dst_maxburst > PL330_MAX_BURST)
+ pch->burst_len = PL330_MAX_BURST;
+ else
+ pch->burst_len = slave_config->dst_maxburst;
+ } else
+ pch->burst_len = 1;
} else if (slave_config->direction == DMA_DEV_TO_MEM) {
if (slave_config->src_addr)
pch->fifo_addr = slave_config->src_addr;
if (slave_config->src_addr_width)
pch->burst_sz = __ffs(slave_config->src_addr_width);
- if (slave_config->src_maxburst)
- pch->burst_len = slave_config->src_maxburst;
+ if (pch->dmac->quirks & PL330_QUIRK_BROKEN_NO_FLUSHP)
+ pch->burst_len = 1;
+ else if (slave_config->src_maxburst) {
+ if (slave_config->src_maxburst > PL330_MAX_BURST)
+ pch->burst_len = PL330_MAX_BURST;
+ else
+ pch->burst_len = slave_config->src_maxburst;
+ } else
+ pch->burst_len = 1;
}

return 0;
@@ -2517,14 +2585,8 @@ static inline int get_burst_len(struct dma_pl330_desc *desc, size_t len)
burst_len >>= desc->rqcfg.brst_size;

/* src/dst_burst_len can't be more than 16 */
- if (burst_len > 16)
- burst_len = 16;
-
- while (burst_len > 1) {
- if (!(len % (burst_len << desc->rqcfg.brst_size)))
- break;
- burst_len--;
- }
+ if (burst_len > PL330_MAX_BURST)
+ burst_len = PL330_MAX_BURST;

return burst_len;
}
@@ -2596,7 +2658,7 @@ static struct dma_async_tx_descriptor *pl330_prep_dma_cyclic(

desc->rqtype = direction;
desc->rqcfg.brst_size = pch->burst_sz;
- desc->rqcfg.brst_len = 1;
+ desc->rqcfg.brst_len = pch->burst_len;
desc->bytes_requested = period_len;
fill_px(&desc->px, dst, src, period_len);

@@ -2741,7 +2803,7 @@ pl330_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
}

desc->rqcfg.brst_size = pch->burst_sz;
- desc->rqcfg.brst_len = 1;
+ desc->rqcfg.brst_len = pch->burst_len;
desc->rqtype = direction;
desc->bytes_requested = sg_dma_len(sg);
}
--
2.11.0

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