[PATCH v4 1/3] spi: imx: GPIO chip select DT property should not be required

[Trent Piepho]

The driver will fail to load if the device tree property for gpio chip
selects is not specified.  Change the driver to make the property optional.
Also have the driver respect the "num-cs" property in the standard way.

This way one can use the native CS lines using standard bindings instead of
being forced to specify a gpio-cs of <0>.

Since native CS do not work in a commonly useful manner with this
hardware/driver, note in the documention that most users probably should
use GPIO based CS lines rather than native.

CC: Mark Brown <broonie at kernel.org>
CC: Shawn Guo <shawnguo at kernel.org>
CC: Sascha Hauer <kernel at pengutronix.de>
CC: Fabio Estevam <fabio.estevam at nxp.com>
CC: Oleksij Rempel <o.rempel at pengutronix.de>
Signed-off-by: Trent Piepho <tpiepho at impinj.com>
---
 Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt | 18 ++++++++++++------
 drivers/spi/spi-imx.c                                  | 18 ++++++++++--------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt b/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
index 5bf13960f7f4..e3c48b20b1a6 100644
--- a/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
+++ b/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
@@ -12,24 +12,30 @@ Required properties:
   - "fsl,imx53-ecspi" for SPI compatible with the one integrated on i.MX53 and later Soc
 - reg : Offset and length of the register set for the device
 - interrupts : Should contain CSPI/eCSPI interrupt
-- cs-gpios : Specifies the gpio pins to be used for chipselects.
 - clocks : Clock specifiers for both ipg and per clocks.
 - clock-names : Clock names should include both "ipg" and "per"
 See the clock consumer binding,
 	Documentation/devicetree/bindings/clock/clock-bindings.txt
-- dmas: DMA specifiers for tx and rx dma. See the DMA client binding,
-		Documentation/devicetree/bindings/dma/dma.txt
-- dma-names: DMA request names should include "tx" and "rx" if present.
 
-Obsolete properties:
-- fsl,spi-num-chipselects : Contains the number of the chipselect
+Recommended properties:
+- cs-gpios : GPIOs to use as chip selects, see spi-bus.txt.  While the native chip
+select lines can be used, they appear to always generate a pulse between each
+word of a transfer.  Most use cases will require GPIO based chip selects to
+generate a valid transaction.
 
 Optional properties:
+- num-cs :  Number of total chip selects, see spi-bus.txt.
+- dmas: DMA specifiers for tx and rx dma. See the DMA client binding,
+Documentation/devicetree/bindings/dma/dma.txt.
+- dma-names: DMA request names, if present, should include "tx" and "rx".
 - 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).
 
+Obsolete properties:
+- fsl,spi-num-chipselects : Contains the number of the chipselect
+
 Example:
 
 ecspi at 70010000 {
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 301cdb721bad..ad54f8258513 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -1523,6 +1523,7 @@ static int spi_imx_probe(struct platform_device *pdev)
 
 	spi_imx->devtype_data = devtype_data;
 
+	/* Get number of chip selects, either platform data or OF */
 	if (mxc_platform_info) {
 		master->num_chipselect = mxc_platform_info->num_chipselect;
 		master->cs_gpios = devm_kzalloc(&master->dev,
@@ -1532,7 +1533,13 @@ static int spi_imx_probe(struct platform_device *pdev)
 
 		for (i = 0; i < master->num_chipselect; i++)
 			master->cs_gpios[i] = mxc_platform_info->chipselect[i];
- 	}
+	} else {
+		u32 num_cs;
+
+		if (!of_property_read_u32(np, "num-cs", &num_cs))
+			master->num_chipselect = num_cs;
+		/* If not preset, default value of 1 is used */
+	}
 
 	spi_imx->bitbang.chipselect = spi_imx_chipselect;
 	spi_imx->bitbang.setup_transfer = spi_imx_setupxfer;
@@ -1619,13 +1626,8 @@ static int spi_imx_probe(struct platform_device *pdev)
 		goto out_clk_put;
 	}
 
-	if (!spi_imx->slave_mode) {
-		if (!master->cs_gpios) {
-			dev_err(&pdev->dev, "No CS GPIOs available\n");
-			ret = -EINVAL;
-			goto out_clk_put;
-		}
-
+	/* Request GPIO CS lines, if any */
+	if (!spi_imx->slave_mode && master->cs_gpios) {
 		for (i = 0; i < master->num_chipselect; i++) {
 			if (!gpio_is_valid(master->cs_gpios[i]))
 				continue;
-- 
2.14.3