spi-imx: Implements handling of the SPI_READY mode flag.

This patch implements consideration of the SPI_READY mode flag as
defined in spi.h. It extends the device tree bindings to support
the values defined by the reference manual for the DRCTL field.

Thus supporting edge-triggered and level-triggered bursts.

Signed-off-by: Leif Middelschulte <Leif.Middelschulte@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt

@@ -23,6 +23,12 @@ See the clock consumer binding,
 Obsolete properties:
 - fsl,spi-num-chipselects : Contains the number of the chipselect
 
+Optional properties:
+- fsl,spi-rdy-drctl: Integer, representing the value of DRCTL, the register
+controlling the SPI_READY handling. Note that to enable the DRCTL consideration,
+the SPI_READY mode-flag needs to be set too.
+Valid values are: 0 (disabled), 1 (edge-triggered burst) and 2 (level-triggered burst).
+
 Example:
 
 ecspi@70010000 {
@@ -35,4 +41,5 @@ ecspi@70010000 {
 		   <&gpio3 25 0>; /* GPIO3_25 */
 	dmas = <&sdma 3 7 1>, <&sdma 4 7 2>;
 	dma-names = "rx", "tx";
+	fsl,spi-rdy-drctl = <1>;
 };

drivers/spi/spi-imx.c

@@ -95,6 +95,7 @@ struct spi_imx_data {
 	unsigned int spi_bus_clk;
 
 	unsigned int bytes_per_word;
+	unsigned int spi_drctl;
 
 	unsigned int count;
 	void (*tx)(struct spi_imx_data *);
@@ -246,6 +247,7 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 #define MX51_ECSPI_CTRL_XCH		(1 <<  2)
 #define MX51_ECSPI_CTRL_SMC		(1 << 3)
 #define MX51_ECSPI_CTRL_MODE_MASK	(0xf << 4)
+#define MX51_ECSPI_CTRL_DRCTL(drctl)	((drctl) << 16)
 #define MX51_ECSPI_CTRL_POSTDIV_OFFSET	8
 #define MX51_ECSPI_CTRL_PREDIV_OFFSET	12
 #define MX51_ECSPI_CTRL_CS(cs)		((cs) << 18)
@@ -355,6 +357,12 @@ static int mx51_ecspi_config(struct spi_device *spi,
 	 */
 	ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
 
+	/*
+	 * Enable SPI_RDY handling (falling edge/level triggered).
+	 */
+	if (spi->mode & SPI_READY)
+		ctrl |= MX51_ECSPI_CTRL_DRCTL(spi_imx->spi_drctl);
+
 	/* set clock speed */
 	ctrl |= mx51_ecspi_clkdiv(spi_imx, config->speed_hz, &clk);
 	spi_imx->spi_bus_clk = clk;
@@ -1173,7 +1181,7 @@ static int spi_imx_probe(struct platform_device *pdev)
 	struct spi_master *master;
 	struct spi_imx_data *spi_imx;
 	struct resource *res;
-	int i, ret, irq;
+	int i, ret, irq, spi_drctl;
 
 	if (!np && !mxc_platform_info) {
 		dev_err(&pdev->dev, "can't get the platform data\n");
@@ -1181,6 +1189,12 @@ static int spi_imx_probe(struct platform_device *pdev)
 	}
 
 	master = spi_alloc_master(&pdev->dev, sizeof(struct spi_imx_data));
+	ret = of_property_read_u32(np, "fsl,spi-rdy-drctl", &spi_drctl);
+	if ((ret < 0) || (spi_drctl >= 0x3)) {
+		/* '11' is reserved */
+		spi_drctl = 0;
+	}
+
 	if (!master)
 		return -ENOMEM;
 
@@ -1216,7 +1230,9 @@ static int spi_imx_probe(struct platform_device *pdev)
 	spi_imx->bitbang.master->unprepare_message = spi_imx_unprepare_message;
 	spi_imx->bitbang.master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
 	if (is_imx35_cspi(spi_imx) || is_imx51_ecspi(spi_imx))
-		spi_imx->bitbang.master->mode_bits |= SPI_LOOP;
+		spi_imx->bitbang.master->mode_bits |= SPI_LOOP | SPI_READY;
+
+	spi_imx->spi_drctl = spi_drctl;
 
 	init_completion(&spi_imx->xfer_done);