dmaengine: stm32-dma: take address into account when computing max width

DMA_SxPAR or DMA_SxM0AR/M1AR registers have to be aligned on PSIZE or MSIZE
respectively. This means that bus width needs to be forced to 1 byte when
computed width is not aligned with address.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Link: https://lore.kernel.org/r/20201120143320.30367-4-amelie.delaunay@st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-dma.c

@@ -264,9 +264,11 @@ static int stm32_dma_get_width(struct stm32_dma_chan *chan,
 }
 
 static enum dma_slave_buswidth stm32_dma_get_max_width(u32 buf_len,
+						       dma_addr_t buf_addr,
 						       u32 threshold)
 {
 	enum dma_slave_buswidth max_width;
+	u64 addr = buf_addr;
 
 	if (threshold == STM32_DMA_FIFO_THRESHOLD_FULL)
 		max_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
@@ -277,6 +279,9 @@ static enum dma_slave_buswidth stm32_dma_get_max_width(u32 buf_len,
 	       max_width > DMA_SLAVE_BUSWIDTH_1_BYTE)
 		max_width = max_width >> 1;
 
+	if (do_div(addr, max_width))
+		max_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+
 	return max_width;
 }
 
@@ -707,7 +712,7 @@ static void stm32_dma_issue_pending(struct dma_chan *c)
 static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
 				    enum dma_transfer_direction direction,
 				    enum dma_slave_buswidth *buswidth,
-				    u32 buf_len)
+				    u32 buf_len, dma_addr_t buf_addr)
 {
 	enum dma_slave_buswidth src_addr_width, dst_addr_width;
 	int src_bus_width, dst_bus_width;
@@ -739,7 +744,8 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
 			return dst_burst_size;
 
 		/* Set memory data size */
-		src_addr_width = stm32_dma_get_max_width(buf_len, fifoth);
+		src_addr_width = stm32_dma_get_max_width(buf_len, buf_addr,
+							 fifoth);
 		chan->mem_width = src_addr_width;
 		src_bus_width = stm32_dma_get_width(chan, src_addr_width);
 		if (src_bus_width < 0)
@@ -788,7 +794,8 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
 			return src_burst_size;
 
 		/* Set memory data size */
-		dst_addr_width = stm32_dma_get_max_width(buf_len, fifoth);
+		dst_addr_width = stm32_dma_get_max_width(buf_len, buf_addr,
+							 fifoth);
 		chan->mem_width = dst_addr_width;
 		dst_bus_width = stm32_dma_get_width(chan, dst_addr_width);
 		if (dst_bus_width < 0)
@@ -876,7 +883,8 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
 
 	for_each_sg(sgl, sg, sg_len, i) {
 		ret = stm32_dma_set_xfer_param(chan, direction, &buswidth,
-					       sg_dma_len(sg));
+					       sg_dma_len(sg),
+					       sg_dma_address(sg));
 		if (ret < 0)
 			goto err;
 
@@ -944,7 +952,8 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_dma_cyclic(
 		return NULL;
 	}
 
-	ret = stm32_dma_set_xfer_param(chan, direction, &buswidth, period_len);
+	ret = stm32_dma_set_xfer_param(chan, direction, &buswidth, period_len,
+				       buf_addr);
 	if (ret < 0)
 		return NULL;