dmaengine: dw: revisit data_width property

There several changes are done here:

- Convert the property to be in bytes

  Besides that this is a common practice for such property, the use of a value
  in bytes much more convenient than handling the encoded one.

- Rename data_width to data-width in the device tree bindings

  The change leaves the support for the old format as well just in case someone
  will use a newer kernel with an old device tree blob.

- While here, replace dwc_fast_ffs() by __ffs()

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Documentation/devicetree/bindings/dma/snps-dma.txt

@@ -13,6 +13,11 @@ Required properties:
 - chan_priority: priority of channels. 0 (default): increase from chan 0->n, 1:
   increase from chan n->0
 - block_size: Maximum block size supported by the controller
+- data-width: Maximum data width supported by hardware per AHB master
+  (in bytes, power of 2)
+
+
+Deprecated properties:
 - data_width: Maximum data width supported by hardware per AHB master
   (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
 
@@ -38,7 +43,7 @@ Example:
 		chan_allocation_order = <1>;
 		chan_priority = <1>;
 		block_size = <0xfff>;
-		data_width = <3 3>;
+		data-width = <8 8>;
 	};
 
 DMA clients connected to the Designware DMA controller must use the format

arch/arc/boot/dts/abilis_tb10x.dtsi

@@ -112,7 +112,7 @@
 			chan_allocation_order = <0>;
 			chan_priority = <1>;
 			block_size = <0x7ff>;
-			data_width = <2>;
+			data-width = <4>;
 			clocks = <&ahb_clk>;
 			clock-names = "hclk";
 		};

arch/arm/boot/dts/spear13xx.dtsi

@@ -117,7 +117,7 @@
 			chan_priority = <1>;
 			block_size = <0xfff>;
 			dma-masters = <2>;
-			data_width = <3 3>;
+			data-width = <8 8>;
 		};
 
 		dma@eb000000 {
@@ -133,7 +133,7 @@
 			chan_allocation_order = <1>;
 			chan_priority = <1>;
 			block_size = <0xfff>;
-			data_width = <3 3>;
+			data-width = <8 8>;
 		};
 
 		fsmc: flash@b0000000 {

drivers/dma/dw/core.c

@@ -162,21 +162,6 @@ static void dwc_initialize(struct dw_dma_chan *dwc)
 
 /*----------------------------------------------------------------------*/
 
-static inline unsigned int dwc_fast_ffs(unsigned long long v)
-{
-	/*
-	 * We can be a lot more clever here, but this should take care
-	 * of the most common optimization.
-	 */
-	if (!(v & 7))
-		return 3;
-	else if (!(v & 3))
-		return 2;
-	else if (!(v & 1))
-		return 1;
-	return 0;
-}
-
 static inline void dwc_dump_chan_regs(struct dw_dma_chan *dwc)
 {
 	dev_err(chan2dev(&dwc->chan),
@@ -677,11 +662,12 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 	struct dw_desc		*prev;
 	size_t			xfer_count;
 	size_t			offset;
+	u8			m_master = dwc->m_master;
 	unsigned int		src_width;
 	unsigned int		dst_width;
-	unsigned int		data_width;
+	unsigned int		data_width = dw->data_width[m_master];
 	u32			ctllo;
-	u8			lms = DWC_LLP_LMS(dwc->m_master);
+	u8			lms = DWC_LLP_LMS(m_master);
 
 	dev_vdbg(chan2dev(chan),
 			"%s: d%pad s%pad l0x%zx f0x%lx\n", __func__,
@@ -694,10 +680,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 
 	dwc->direction = DMA_MEM_TO_MEM;
 
-	data_width = dw->data_width[dwc->m_master];
-
-	src_width = dst_width = min_t(unsigned int, data_width,
-				      dwc_fast_ffs(src | dest | len));
+	src_width = dst_width = __ffs(data_width | src | dest | len);
 
 	ctllo = DWC_DEFAULT_CTLLO(chan)
 			| DWC_CTLL_DST_WIDTH(dst_width)
@@ -757,11 +740,12 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	struct dw_desc		*prev;
 	struct dw_desc		*first;
 	u32			ctllo;
-	u8			lms = DWC_LLP_LMS(dwc->m_master);
+	u8			m_master = dwc->m_master;
+	u8			lms = DWC_LLP_LMS(m_master);
 	dma_addr_t		reg;
 	unsigned int		reg_width;
 	unsigned int		mem_width;
-	unsigned int		data_width;
+	unsigned int		data_width = dw->data_width[m_master];
 	unsigned int		i;
 	struct scatterlist	*sg;
 	size_t			total_len = 0;
@@ -787,8 +771,6 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		ctllo |= sconfig->device_fc ? DWC_CTLL_FC(DW_DMA_FC_P_M2P) :
 			DWC_CTLL_FC(DW_DMA_FC_D_M2P);
 
-		data_width = dw->data_width[dwc->m_master];
-
 		for_each_sg(sgl, sg, sg_len, i) {
 			struct dw_desc	*desc;
 			u32		len, dlen, mem;
@@ -796,8 +778,7 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			mem_width = min_t(unsigned int,
-					  data_width, dwc_fast_ffs(mem | len));
+			mem_width = __ffs(data_width | mem | len);
 
 slave_sg_todev_fill_desc:
 			desc = dwc_desc_get(dwc);
@@ -843,8 +824,6 @@ slave_sg_todev_fill_desc:
 		ctllo |= sconfig->device_fc ? DWC_CTLL_FC(DW_DMA_FC_P_P2M) :
 			DWC_CTLL_FC(DW_DMA_FC_D_P2M);
 
-		data_width = dw->data_width[dwc->m_master];
-
 		for_each_sg(sgl, sg, sg_len, i) {
 			struct dw_desc	*desc;
 			u32		len, dlen, mem;
@@ -852,8 +831,7 @@ slave_sg_todev_fill_desc:
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			mem_width = min_t(unsigned int,
-					  data_width, dwc_fast_ffs(mem | len));
+			mem_width = __ffs(data_width | mem | len);
 
 slave_sg_fromdev_fill_desc:
 			desc = dwc_desc_get(dwc);
@@ -1500,7 +1478,7 @@ int dw_dma_probe(struct dw_dma_chip *chip, struct dw_dma_platform_data *pdata)
 		pdata->nr_masters = (dw_params >> DW_PARAMS_NR_MASTER & 3) + 1;
 		for (i = 0; i < pdata->nr_masters; i++) {
 			pdata->data_width[i] =
-				(dw_params >> DW_PARAMS_DATA_WIDTH(i) & 3) + 2;
+				4 << (dw_params >> DW_PARAMS_DATA_WIDTH(i) & 3);
 		}
 		max_blk_size = dma_readl(dw, MAX_BLK_SIZE);
 

drivers/dma/dw/platform.c

@@ -138,9 +138,12 @@ dw_dma_parse_dt(struct platform_device *pdev)
 	if (!of_property_read_u32(np, "block_size", &tmp))
 		pdata->block_size = tmp;
 
-	if (!of_property_read_u32_array(np, "data_width", arr, nr_masters)) {
+	if (!of_property_read_u32_array(np, "data-width", arr, nr_masters)) {
 		for (tmp = 0; tmp < nr_masters; tmp++)
 			pdata->data_width[tmp] = arr[tmp];
+	} else if (!of_property_read_u32_array(np, "data_width", arr, nr_masters)) {
+		for (tmp = 0; tmp < nr_masters; tmp++)
+			pdata->data_width[tmp] = BIT(arr[tmp] & 0x07);
 	}
 
 	return pdata;

include/linux/platform_data/dma-dw.h

@@ -43,7 +43,7 @@ struct dw_dma_slave {
  * @block_size: Maximum block size supported by the controller
  * @nr_masters: Number of AHB masters supported by the controller
  * @data_width: Maximum data width supported by hardware per AHB master
- *		(0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
+ *		(in bytes, power of 2)
  */
 struct dw_dma_platform_data {
 	unsigned int	nr_channels;