[PATCH v2] spi: dw: Add 32 bpw support to DW DMA Controller

[Joy Chakraborty]

If DW Controller is capable of a maximum of 32 bits per word then SW or
DMA controller has to write up to 32bit or 4byte data to the FIFO at a
time.

This Patch adds support for AxSize = 4 bytes configuration from dw dma
driver if n_bytes i.e. number of bytes per write to fifo is 3 or 4.
It also checks to see if the dma controller is capable of satisfying the
width requirement to achieve a particular bits/word requirement per
transfer.

Signed-off-by: Joy Chakraborty <joychakr@xxxxxxxxxx>
---
 drivers/spi/spi-dw-dma.c | 37 ++++++++++++++++++++++++++++++++-----
 drivers/spi/spi-dw.h     |  1 +
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-dw-dma.c b/drivers/spi/spi-dw-dma.c
index ababb910b391..9ac3a1c25e2d 100644
--- a/drivers/spi/spi-dw-dma.c
+++ b/drivers/spi/spi-dw-dma.c
@@ -23,6 +23,8 @@
 #define DW_SPI_TX_BUSY		1
 #define DW_SPI_TX_BURST_LEVEL	16
 
+static inline enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes);
+
 static bool dw_spi_dma_chan_filter(struct dma_chan *chan, void *param)
 {
 	struct dw_dma_slave *s = param;
@@ -89,6 +91,16 @@ static void dw_spi_dma_sg_burst_init(struct dw_spi *dws)
 		dws->dma_sg_burst = 0;
 }
 
+static void dw_spi_dma_addr_widths_init(struct dw_spi *dws)
+{
+	struct dma_slave_caps tx = {0}, rx = {0};
+
+	dma_get_slave_caps(dws->txchan, &tx);
+	dma_get_slave_caps(dws->rxchan, &rx);
+
+	dws->dma_addr_widths = tx.dst_addr_widths & rx.src_addr_widths;
+}
+
 static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 {
 	struct dw_dma_slave dma_tx = { .dst_id = 1 }, *tx = &dma_tx;
@@ -128,6 +140,8 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 
 	dw_spi_dma_sg_burst_init(dws);
 
+	dw_spi_dma_addr_widths_init(dws);
+
 	pci_dev_put(dma_dev);
 
 	return 0;
@@ -167,6 +181,8 @@ static int dw_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
 
 	dw_spi_dma_sg_burst_init(dws);
 
+	dw_spi_dma_addr_widths_init(dws);
+
 	return 0;
 
 free_rxchan:
@@ -202,18 +218,29 @@ static bool dw_spi_can_dma(struct spi_controller *master,
 			   struct spi_device *spi, struct spi_transfer *xfer)
 {
 	struct dw_spi *dws = spi_controller_get_devdata(master);
+	enum dma_slave_buswidth dma_bus_width;
 
-	return xfer->len > dws->fifo_len;
+	if (xfer->len > dws->fifo_len) {
+		dma_bus_width = dw_spi_dma_convert_width(dws->n_bytes);
+		if (dws->dma_addr_widths & BIT(dma_bus_width))
+			return true;
+	}
+	return false;
 }
 
 static enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes)
 {
-	if (n_bytes == 1)
+	switch (n_bytes) {
+	case 1:
 		return DMA_SLAVE_BUSWIDTH_1_BYTE;
-	else if (n_bytes == 2)
+	case 2:
 		return DMA_SLAVE_BUSWIDTH_2_BYTES;
-
-	return DMA_SLAVE_BUSWIDTH_UNDEFINED;
+	case 3:
+	case 4:
+		return DMA_SLAVE_BUSWIDTH_4_BYTES;
+	default:
+		return DMA_SLAVE_BUSWIDTH_UNDEFINED;
+	}
 }
 
 static int dw_spi_dma_wait(struct dw_spi *dws, unsigned int len, u32 speed)
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 9e8eb2b52d5c..3962e6dcf880 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -190,6 +190,7 @@ struct dw_spi {
 	struct dma_chan		*rxchan;
 	u32			rxburst;
 	u32			dma_sg_burst;
+	u32			dma_addr_widths;
 	unsigned long		dma_chan_busy;
 	dma_addr_t		dma_addr; /* phy address of the Data register */
 	const struct dw_spi_dma_ops *dma_ops;
-- 
2.40.0.rc1.284.g88254d51c5-goog