linux-kernel - [PATCH 3/4] dmaengine: dw: Simplify prepare CTL

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Date: Tue, 16 Apr 2024 19:28:57 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Viresh Kumar <vireshk@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Vinod Koul <vkoul@...nel.org>
Cc: Serge Semin <fancer.lancer@...il.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	dmaengine@...r.kernel.org,
	linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] dmaengine: dw: Simplify prepare CTL_LO methods

Currently the CTL LO fields are calculated on the platform-specific basis.
It's implemented by means of the prepare_ctllo() callbacks using the
ternary operator within the local variables init block at the beginning of
the block scope. The functions code currently is relatively hard to
comprehend and isn't that optimal since implies four conditional
statements executed and two additional local variables defined. Let's
simplify the DW AHB DMA prepare_ctllo() method by unrolling the ternary
operators into the normal if-else statement, dropping redundant
master-interface ID variables and initializing the local variables based
on the singly evaluated DMA-transfer direction check. Thus the method will
look much more readable since now the fields content can be easily
inferred right from the if-else branch. Provide the same update in the
Intel DMA32 core driver for sake of the driver code unification.

Note besides of the effects described above this update is basically a
preparation before dropping the max burst encoding callback. It will
require calling the burst fields calculation methods right in the
prepare_ctllo() callbacks, which would have made the later function code
even more complex.

Signed-off-by: Serge Semin <fancer.lancer@...il.com>
---
 drivers/dma/dw/dw.c     | 24 ++++++++++++++++++------
 drivers/dma/dw/idma32.c | 14 ++++++++++++--
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/dw/dw.c b/drivers/dma/dw/dw.c
index a4862263ff14..c65438d1f1ff 100644
--- a/drivers/dma/dw/dw.c
+++ b/drivers/dma/dw/dw.c
@@ -67,12 +67,24 @@ static size_t dw_dma_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width)
 static u32 dw_dma_prepare_ctllo(struct dw_dma_chan *dwc)
 {
 	struct dma_slave_config	*sconfig = &dwc->dma_sconfig;
-	u8 smsize = (dwc->direction == DMA_DEV_TO_MEM) ? sconfig->src_maxburst : 0;
-	u8 dmsize = (dwc->direction == DMA_MEM_TO_DEV) ? sconfig->dst_maxburst : 0;
-	u8 p_master = dwc->dws.p_master;
-	u8 m_master = dwc->dws.m_master;
-	u8 dms = (dwc->direction == DMA_MEM_TO_DEV) ? p_master : m_master;
-	u8 sms = (dwc->direction == DMA_DEV_TO_MEM) ? p_master : m_master;
+	u8 sms, smsize, dms, dmsize;
+
+	if (dwc->direction == DMA_MEM_TO_DEV) {
+		sms = dwc->dws.m_master;
+		smsize = 0;
+		dms = dwc->dws.p_master;
+		dmsize = sconfig->dst_maxburst;
+	} else if (dwc->direction == DMA_DEV_TO_MEM) {
+		sms = dwc->dws.p_master;
+		smsize = sconfig->src_maxburst;
+		dms = dwc->dws.m_master;
+		dmsize = 0;
+	} else /* DMA_MEM_TO_MEM */ {
+		sms = dwc->dws.m_master;
+		smsize = 0;
+		dms = dwc->dws.m_master;
+		dmsize = 0;
+	}
 
 	return DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN |
 	       DWC_CTLL_DST_MSIZE(dmsize) | DWC_CTLL_SRC_MSIZE(smsize) |
diff --git a/drivers/dma/dw/idma32.c b/drivers/dma/dw/idma32.c
index 58f4078d83fe..3a1b12517655 100644
--- a/drivers/dma/dw/idma32.c
+++ b/drivers/dma/dw/idma32.c
@@ -202,8 +202,18 @@ static size_t idma32_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width)
 static u32 idma32_prepare_ctllo(struct dw_dma_chan *dwc)
 {
 	struct dma_slave_config	*sconfig = &dwc->dma_sconfig;
-	u8 smsize = (dwc->direction == DMA_DEV_TO_MEM) ? sconfig->src_maxburst : 0;
-	u8 dmsize = (dwc->direction == DMA_MEM_TO_DEV) ? sconfig->dst_maxburst : 0;
+	u8 smsize, dmsize;
+
+	if (dwc->direction == DMA_MEM_TO_DEV) {
+		smsize = 0;
+		dmsize = sconfig->dst_maxburst;
+	} else if (dwc->direction == DMA_DEV_TO_MEM) {
+		smsize = sconfig->src_maxburst;
+		dmsize = 0;
+	} else /* DMA_MEM_TO_MEM */ {
+		smsize = 0;
+		dmsize = 0;
+	}
 
 	return DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN |
 	       DWC_CTLL_DST_MSIZE(dmsize) | DWC_CTLL_SRC_MSIZE(smsize);
-- 
2.43.0