spi: dw: Parameterize the DMA Rx/Tx burst length

It isn't good to have numeric literals in the code especially if there
are multiple of them and they are related. Let's replace the Tx and Rx
burst level literals with the corresponding constants.
Co-developed-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-7-Sergey.Semin@baikalelectronics.ruSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-mid.c

@@ -21,7 +21,9 @@
 
 #define WAIT_RETRIES	5
 #define RX_BUSY		0
+#define RX_BURST_LEVEL	16
 #define TX_BUSY		1
+#define TX_BURST_LEVEL	16
 
 static bool mid_spi_dma_chan_filter(struct dma_chan *chan, void *param)
 {
@@ -227,7 +229,7 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_tx(struct dw_spi *dws,
 	memset(&txconf, 0, sizeof(txconf));
 	txconf.direction = DMA_MEM_TO_DEV;
 	txconf.dst_addr = dws->dma_addr;
-	txconf.dst_maxburst = 16;
+	txconf.dst_maxburst = TX_BURST_LEVEL;
 	txconf.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	txconf.dst_addr_width = convert_dma_width(dws->n_bytes);
 	txconf.device_fc = false;
@@ -319,7 +321,7 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi *dws,
 	memset(&rxconf, 0, sizeof(rxconf));
 	rxconf.direction = DMA_DEV_TO_MEM;
 	rxconf.src_addr = dws->dma_addr;
-	rxconf.src_maxburst = 16;
+	rxconf.src_maxburst = RX_BURST_LEVEL;
 	rxconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	rxconf.src_addr_width = convert_dma_width(dws->n_bytes);
 	rxconf.device_fc = false;
@@ -344,8 +346,8 @@ static int mid_spi_dma_setup(struct dw_spi *dws, struct spi_transfer *xfer)
 {
 	u16 imr = 0, dma_ctrl = 0;
 
-	dw_writel(dws, DW_SPI_DMARDLR, 0xf);
-	dw_writel(dws, DW_SPI_DMATDLR, 0x10);
+	dw_writel(dws, DW_SPI_DMARDLR, RX_BURST_LEVEL - 1);
+	dw_writel(dws, DW_SPI_DMATDLR, TX_BURST_LEVEL);
 
 	if (xfer->tx_buf) {
 		dma_ctrl |= SPI_DMA_TDMAE;