[PATCH RFC 04/11] dmaengine: bcm2835: move CB info generation into separate function

[Stefan Wahren]

Actually the generation of the Control Block info follows some simple
rules. So handle this with a separate function to avoid open coding
for every DMA operation. Another advantage is that we can easier
introduce other platforms with different info bits.

Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
---
 drivers/dma/bcm2835-dma.c | 51 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index adfe6bc..10c9ba2 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -201,6 +201,35 @@ static inline struct bcm2835_desc *to_bcm2835_dma_desc(
 	return container_of(t, struct bcm2835_desc, vd.tx);
 }
 
+static u32 bcm2835_dma_prepare_cb_info(struct bcm2835_chan *c,
+				       enum dma_transfer_direction direction,
+				       bool zero_page)
+{
+	u32 result;
+
+	if (direction == DMA_MEM_TO_MEM)
+		return BCM2835_DMA_D_INC | BCM2835_DMA_S_INC;
+
+	result = BCM2835_DMA_WAIT_RESP;
+
+	/* Setup DREQ channel */
+	if (c->dreq != 0)
+		result |= BCM2835_DMA_PER_MAP(c->dreq);
+
+	if (direction == DMA_DEV_TO_MEM) {
+		result |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
+	} else {
+		result |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
+
+		/* non-lite channels can write zeroes w/o accessing memory */
+		if (zero_page && !c->is_lite_channel) {
+			result |= BCM2835_DMA_S_IGNORE;
+		}
+	}
+
+	return result;
+}
+
 static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
 {
 	size_t i;
@@ -615,7 +644,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_memcpy(
 {
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	struct bcm2835_desc *d;
-	u32 info = BCM2835_DMA_D_INC | BCM2835_DMA_S_INC;
+	u32 info = bcm2835_dma_prepare_cb_info(c, DMA_MEM_TO_MEM, false);
 	u32 extra = BCM2835_DMA_INT_EN | BCM2835_DMA_WAIT_RESP;
 	size_t max_len = bcm2835_dma_max_frame_length(c);
 	size_t frames;
@@ -646,7 +675,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	struct bcm2835_desc *d;
 	dma_addr_t src = 0, dst = 0;
-	u32 info = BCM2835_DMA_WAIT_RESP;
+	u32 info = bcm2835_dma_prepare_cb_info(c, direction, false);
 	u32 extra = BCM2835_DMA_INT_EN;
 	size_t frames;
 
@@ -656,19 +685,14 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
 		return NULL;
 	}
 
-	if (c->dreq != 0)
-		info |= BCM2835_DMA_PER_MAP(c->dreq);
-
 	if (direction == DMA_DEV_TO_MEM) {
 		if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
 			return NULL;
 		src = c->cfg.src_addr;
-		info |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
 	} else {
 		if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
 			return NULL;
 		dst = c->cfg.dst_addr;
-		info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
 	}
 
 	/* count frames in sg list */
@@ -698,7 +722,8 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	struct bcm2835_desc *d;
 	dma_addr_t src, dst;
-	u32 info = BCM2835_DMA_WAIT_RESP;
+	u32 info = bcm2835_dma_prepare_cb_info(c, direction,
+					       buf_addr == od->zero_page);
 	u32 extra = 0;
 	size_t max_len = bcm2835_dma_max_frame_length(c);
 	size_t frames;
@@ -729,26 +754,16 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
 			      "%s: buffer_length (%zd) is not a multiple of period_len (%zd)\n",
 			      __func__, buf_len, period_len);
 
-	/* Setup DREQ channel */
-	if (c->dreq != 0)
-		info |= BCM2835_DMA_PER_MAP(c->dreq);
-
 	if (direction == DMA_DEV_TO_MEM) {
 		if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
 			return NULL;
 		src = c->cfg.src_addr;
 		dst = buf_addr;
-		info |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
 	} else {
 		if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
 			return NULL;
 		dst = c->cfg.dst_addr;
 		src = buf_addr;
-		info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
-
-		/* non-lite channels can write zeroes w/o accessing memory */
-		if (buf_addr == od->zero_page && !c->is_lite_channel)
-			info |= BCM2835_DMA_S_IGNORE;
 	}
 
 	/* calculate number of frames */
-- 
2.7.4