spi/ep93xx: add DMA support

This patch adds DMA support for the EP93xx SPI driver. By default the DMA is
not enabled but it can be enabled by setting ep93xx_spi_info.use_dma to true
in board configuration file.

Note that the SPI driver still uses PIO for small transfers (<= 8 bytes) for
performance reasons.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

Documentation/spi/ep93xx_spi

@@ -88,6 +88,16 @@ static void __init ts72xx_init_machine(void)
 			    ARRAY_SIZE(ts72xx_spi_devices));
 }
 
+The driver can use DMA for the transfers also. In this case ts72xx_spi_info
+becomes:
+
+static struct ep93xx_spi_info ts72xx_spi_info = {
+	.num_chipselect	= ARRAY_SIZE(ts72xx_spi_devices),
+	.use_dma	= true;
+};
+
+Note that CONFIG_EP93XX_DMA should be enabled as well.
+
 Thanks to
 =========
 Martin Guy, H. Hartley Sweeten and others who helped me during development of

arch/arm/mach-ep93xx/core.c

@@ -488,11 +488,15 @@ static struct resource ep93xx_spi_resources[] = {
 	},
 };
 
+static u64 ep93xx_spi_dma_mask = DMA_BIT_MASK(32);
+
 static struct platform_device ep93xx_spi_device = {
 	.name		= "ep93xx-spi",
 	.id		= 0,
 	.dev		= {
-		.platform_data = &ep93xx_spi_master_data,
+		.platform_data		= &ep93xx_spi_master_data,
+		.coherent_dma_mask	= DMA_BIT_MASK(32),
+		.dma_mask		= &ep93xx_spi_dma_mask,
 	},
 	.num_resources	= ARRAY_SIZE(ep93xx_spi_resources),
 	.resource	= ep93xx_spi_resources,

arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h

@@ -7,9 +7,11 @@ struct spi_device;
  * struct ep93xx_spi_info - EP93xx specific SPI descriptor
  * @num_chipselect: number of chip selects on this board, must be
  *                  at least one
+ * @use_dma: use DMA for the transfers
  */
 struct ep93xx_spi_info {
 	int	num_chipselect;
+	bool	use_dma;
 };
 
 /**