[PATCH RESEND v4 5/6] dmaengine: dw: Simplify max-burst calculation procedure

Serge Semin
2024-08-02T07:51:31Z

In order to have a more coherent DW AHB DMA slave configuration method -
dwc_config() - let's simplify the source and destination channel max-burst
calculation procedure:

1. Create the max-burst verification method as it has been just done for
the memory and peripheral address widths. Thus the dwc_config() method
will turn to a set of the verification methods execution.

2. Since both the generic DW AHB DMA and Intel iDMA 32-bit engines support
the power-of-2 bursts only, then the specified by the client driver
max-burst values can be converted to being power-of-2 right in the
max-burst verification method.

3. Since max-burst encoded value is required on the CTL_LO fields
calculation stage, the encode_maxburst() callback can be easily dropped
from the dw_dma structure meanwhile the encoding procedure will be
executed right in the CTL_LO register value calculation.

Thus the update will provide the next positive effects: the internal
DMA-slave config structure will contain only the real DMA-transfer config
values, which will be encoded to the DMA-controller register fields only
when it's required on the buffer mapping; the redundant encode_maxburst()
callback will be dropped simplifying the internal HW-abstraction API;
dwc_config() will look more readable executing the verification functions
one-by-one.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>

---

Changelog v2:
- Refer to dwc_config() in the commit message. (Andy)
- Convert dwc_verify_maxburst() to returning zero. (Andy)
- Add a comment regarding the values utilized in the
dwc_verify_p_buswidth() being verified before the method is called.
(Andy, see patch 2)
- Detach the dw_dma_encode_maxburst() and idma32_encode_maxburst()
movement to a preparatory patch. (Andy)
---
drivers/dma/dw/core.c | 30 +++++++++++++++++++++---------
drivers/dma/dw/dw.c | 9 ++++-----
drivers/dma/dw/idma32.c | 9 ++++-----
drivers/dma/dw/regs.h | 1 -
4 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 4987bfa10461..c696d79b911a 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -779,6 +779,23 @@ bool dw_dma_filter(struct dma_chan *chan, void *param)
}
EXPORT_SYMBOL_GPL(dw_dma_filter);

+static int dwc_verify_maxburst(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+
+ dwc->dma_sconfig.src_maxburst =
+ clamp(dwc->dma_sconfig.src_maxburst, 1U, dwc->max_burst);
+ dwc->dma_sconfig.dst_maxburst =
+ clamp(dwc->dma_sconfig.dst_maxburst, 1U, dwc->max_burst);
+
+ dwc->dma_sconfig.src_maxburst =
+ rounddown_pow_of_two(dwc->dma_sconfig.src_maxburst);
+ dwc->dma_sconfig.dst_maxburst =
+ rounddown_pow_of_two(dwc->dma_sconfig.dst_maxburst);
+
+ return 0;
+}
+
static int dwc_verify_p_buswidth(struct dma_chan *chan)
{
struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
@@ -838,7 +855,7 @@ static int dwc_verify_m_buswidth(struct dma_chan *chan)
dwc->dma_sconfig.src_addr_width = mem_width;
} else if (dwc->dma_sconfig.direction == DMA_DEV_TO_MEM) {
reg_width = dwc->dma_sconfig.src_addr_width;
- reg_burst = rounddown_pow_of_two(dwc->dma_sconfig.src_maxburst);
+ reg_burst = dwc->dma_sconfig.src_maxburst;

dwc->dma_sconfig.dst_addr_width = min(mem_width, reg_width * reg_burst);
}
@@ -849,15 +866,13 @@ static int dwc_verify_m_buswidth(struct dma_chan *chan)
static int dwc_config(struct dma_chan *chan, struct dma_slave_config *sconfig)
{
struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
- struct dw_dma *dw = to_dw_dma(chan->device);
int ret;

memcpy(&dwc->dma_sconfig, sconfig, sizeof(*sconfig));

- dwc->dma_sconfig.src_maxburst =
- clamp(dwc->dma_sconfig.src_maxburst, 1U, dwc->max_burst);
- dwc->dma_sconfig.dst_maxburst =
- clamp(dwc->dma_sconfig.dst_maxburst, 1U, dwc->max_burst);
+ ret = dwc_verify_maxburst(chan);
+ if (ret)
+ return ret;

ret = dwc_verify_p_buswidth(chan);
if (ret)
@@ -867,9 +882,6 @@ static int dwc_config(struct dma_chan *chan, struct dma_slave_config *sconfig)
if (ret)
return ret;

- dw->encode_maxburst(dwc, &dwc->dma_sconfig.src_maxburst);
- dw->encode_maxburst(dwc, &dwc->dma_sconfig.dst_maxburst);
-
return 0;
}

diff --git a/drivers/dma/dw/dw.c b/drivers/dma/dw/dw.c
index 628ee1e77505..6766142884b6 100644
--- a/drivers/dma/dw/dw.c
+++ b/drivers/dma/dw/dw.c
@@ -64,13 +64,13 @@ static size_t dw_dma_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width)
return DWC_CTLH_BLOCK_TS(block) << width;
}

-static void dw_dma_encode_maxburst(struct dw_dma_chan *dwc, u32 *maxburst)
+static inline u8 dw_dma_encode_maxburst(u32 maxburst)
{
/*
* Fix burst size according to dw_dmac. We need to convert them as:
* 1 -> 0, 4 -> 1, 8 -> 2, 16 -> 3.
*/
- *maxburst = *maxburst > 1 ? fls(*maxburst) - 2 : 0;
+ return maxburst > 1 ? fls(maxburst) - 2 : 0;
}

static u32 dw_dma_prepare_ctllo(struct dw_dma_chan *dwc)
@@ -82,11 +82,11 @@ static u32 dw_dma_prepare_ctllo(struct dw_dma_chan *dwc)
if (dwc->direction == DMA_MEM_TO_DEV) {
sms = dwc->dws.m_master;
dms = dwc->dws.p_master;
- dmsize = sconfig->dst_maxburst;
+ dmsize = dw_dma_encode_maxburst(sconfig->dst_maxburst);
} else if (dwc->direction == DMA_DEV_TO_MEM) {
sms = dwc->dws.p_master;
dms = dwc->dws.m_master;
- smsize = sconfig->src_maxburst;
+ smsize = dw_dma_encode_maxburst(sconfig->src_maxburst);
} else /* DMA_MEM_TO_MEM */ {
sms = dwc->dws.m_master;
dms = dwc->dws.m_master;
@@ -125,7 +125,6 @@ int dw_dma_probe(struct dw_dma_chip *chip)
dw->suspend_chan = dw_dma_suspend_chan;
dw->resume_chan = dw_dma_resume_chan;
dw->prepare_ctllo = dw_dma_prepare_ctllo;
- dw->encode_maxburst = dw_dma_encode_maxburst;
dw->bytes2block = dw_dma_bytes2block;
dw->block2bytes = dw_dma_block2bytes;

diff --git a/drivers/dma/dw/idma32.c b/drivers/dma/dw/idma32.c
index 493fcbafa2b8..dac617c183e6 100644
--- a/drivers/dma/dw/idma32.c
+++ b/drivers/dma/dw/idma32.c
@@ -199,9 +199,9 @@ static size_t idma32_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width)
return IDMA32C_CTLH_BLOCK_TS(block);
}

-static void idma32_encode_maxburst(struct dw_dma_chan *dwc, u32 *maxburst)
+static inline u8 idma32_encode_maxburst(u32 maxburst)
{
- *maxburst = *maxburst > 1 ? fls(*maxburst) - 1 : 0;
+ return maxburst > 1 ? fls(maxburst) - 1 : 0;
}

static u32 idma32_prepare_ctllo(struct dw_dma_chan *dwc)
@@ -210,9 +210,9 @@ static u32 idma32_prepare_ctllo(struct dw_dma_chan *dwc)
u8 smsize = 0, dmsize = 0;

if (dwc->direction == DMA_MEM_TO_DEV)
- dmsize = sconfig->dst_maxburst;
+ dmsize = idma32_encode_maxburst(sconfig->dst_maxburst);
else if (dwc->direction == DMA_DEV_TO_MEM)
- smsize = sconfig->src_maxburst;
+ smsize = idma32_encode_maxburst(sconfig->src_maxburst);

return DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN |
DWC_CTLL_DST_MSIZE(dmsize) | DWC_CTLL_SRC_MSIZE(smsize);
@@ -274,7 +274,6 @@ int idma32_dma_probe(struct dw_dma_chip *chip)
dw->suspend_chan = idma32_suspend_chan;
dw->resume_chan = idma32_resume_chan;
dw->prepare_ctllo = idma32_prepare_ctllo;
- dw->encode_maxburst = idma32_encode_maxburst;
dw->bytes2block = idma32_bytes2block;
dw->block2bytes = idma32_block2bytes;

diff --git a/drivers/dma/dw/regs.h b/drivers/dma/dw/regs.h
index 76654bd13c1a..5969d9cc8d7a 100644
--- a/drivers/dma/dw/regs.h
+++ b/drivers/dma/dw/regs.h
@@ -327,7 +327,6 @@ struct dw_dma {
void (*suspend_chan)(struct dw_dma_chan *dwc, bool drain);
void (*resume_chan)(struct dw_dma_chan *dwc, bool drain);
u32 (*prepare_ctllo)(struct dw_dma_chan *dwc);
- void (*encode_maxburst)(struct dw_dma_chan *dwc, u32 *maxburst);
u32 (*bytes2block)(struct dw_dma_chan *dwc, size_t bytes,
unsigned int width, size_t *len);
size_t (*block2bytes)(struct dw_dma_chan *dwc, u32 block, u32 width);
--
2.43.0