[PATCH v2 5/6] dmaengine: dw: Simplify max-burst calculation procedure

[Serge Semin <fancer.lancer@gmail.com>]

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 b341a6f1b043..32a66f9effd9 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