[PATCH v3 1/4] spi: imx: GPIO based chip selects should not be required

[Trent Piepho]

The driver will fail to load if no gpio chip selects are specified,
this patch changes this so that it no longer fails.

It's possible to use all native chip selects, in which case there is
no reason to have a gpio chip select array.  This is what happens if
the *optional* device tree property "cs-gpios" is omitted.

The spi core already checks for the absence of gpio chip selects in
the master and assigns any slaves the gpio_cs value of -ENOENT.

Also have the driver respect the standard SPI device tree property "num-cs"
to allow setting the number of chip selects without using cs-gpios.

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>
---
 drivers/spi/spi-imx.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index fe35aaea323b..76bf0e4fc2c7 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