spi: davinci: remove unnecessary data transmit on CS disable

On TI DaVinci's SPI controller, the SPIDAT1 register which
controls the chip slect status, also has data transmit register
in the lower 16 bits. Writing to the whole 32-bits triggers
an additional data transmit every time the chip select is disabled.

While most SPI slaves cope-up with this, some cannot. This
patch fixes this by doing a 16-bit write on the upper half
of the SPIDAT1 register

While at it, group the SPIGCR1 register related defines seperately
from SPIDAT1 register defines.

Signed-off-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Tested-By: Michael Williamson <michael.williamson@criticallink.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

drivers/spi/davinci_spi.c

@@ -65,9 +65,10 @@
 #define SPI_INTLVL_1		0x000001FFu
 #define SPI_INTLVL_0		0x00000000u
 
-/* SPIDAT1 */
-#define SPIDAT1_CSHOLD_MASK	BIT(28)
-#define SPIDAT1_CSNR_SHIFT	16
+/* SPIDAT1 (upper 16 bit defines) */
+#define SPIDAT1_CSHOLD_MASK	BIT(12)
+
+/* SPIGCR1 */
 #define SPIGCR1_CLKMOD_MASK	BIT(1)
 #define SPIGCR1_MASTER_MASK     BIT(0)
 #define SPIGCR1_LOOPBACK_MASK	BIT(16)
@@ -235,8 +236,8 @@ static void davinci_spi_chipselect(struct spi_device *spi, int value)
 {
 	struct davinci_spi *davinci_spi;
 	struct davinci_spi_platform_data *pdata;
-	u32 data1_reg_val;
 	u8 chip_sel = spi->chip_select;
+	u16 spidat1_cfg = CS_DEFAULT;
 
 	davinci_spi = spi_master_get_devdata(spi->master);
 	pdata = davinci_spi->pdata;
@@ -245,17 +246,12 @@ static void davinci_spi_chipselect(struct spi_device *spi, int value)
 	 * Board specific chip select logic decides the polarity and cs
 	 * line for the controller
 	 */
-	data1_reg_val = CS_DEFAULT << SPIDAT1_CSNR_SHIFT;
 	if (value == BITBANG_CS_ACTIVE) {
-		data1_reg_val |= SPIDAT1_CSHOLD_MASK;
-		data1_reg_val &= ~((0x1 << chip_sel) << SPIDAT1_CSNR_SHIFT);
+		spidat1_cfg |= SPIDAT1_CSHOLD_MASK;
+		spidat1_cfg &= ~(0x1 << chip_sel);
 	}
 
-	iowrite32(data1_reg_val, davinci_spi->base + SPIDAT1);
-	while ((ioread32(davinci_spi->base + SPIBUF)
-				& SPIBUF_RXEMPTY_MASK) == 0)
-		cpu_relax();
-
+	iowrite16(spidat1_cfg, davinci_spi->base + SPIDAT1 + 2);
 }
 
 /**