[PATCH v2] spi: Fix probing SPI drivers with no cs-gpios

[John Watts <contact@jookia.org>]

of_gpio_named_count returns a negative value on error but this
is discarded and cast to a u16, making error handling impossible.

With debug logging enabled this effectively halts booting so the board can
print an error over serial 65534 times.

Introduce of_gpio_count_csgpios which returns 0 in the case of an error
rather than a negative value.

Signed-off-by: John Watts <contact@jookia.org>
---
Changes v1 -> v2:
- Refactored logic in to separate of_gpio_count_csgpios function
---
 drivers/spi/atmel_spi.c |  2 +-
 drivers/spi/imx_spi.c   |  2 +-
 drivers/spi/stm32_spi.c |  2 +-
 include/of_gpio.h       | 17 +++++++++++++++++
 4 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index 399c47c81d..9bf85874c5 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -408,7 +408,7 @@ static int atmel_spi_probe(struct device *dev)
 		master->num_chipselect = pdata->num_chipselect;
 		as->cs_pins = pdata->chipselect;
 	} else {
-		master->num_chipselect = of_gpio_named_count(node, "cs-gpios");
+		master->num_chipselect = of_gpio_count_csgpios(node);
 		as->cs_pins = xzalloc(sizeof(u32) * master->num_chipselect);
 
 		for (i = 0; i < master->num_chipselect; i++) {
diff --git a/drivers/spi/imx_spi.c b/drivers/spi/imx_spi.c
index eb30d757d5..f81d9e851f 100644
--- a/drivers/spi/imx_spi.c
+++ b/drivers/spi/imx_spi.c
@@ -568,7 +568,7 @@ static int imx_spi_dt_probe(struct imx_spi *imx)
 	if (!node)
 		return -ENODEV;
 
-	imx->master.num_chipselect = of_gpio_named_count(node, "cs-gpios");
+	imx->master.num_chipselect = of_gpio_count_csgpios(node);
 	imx->cs_array = xzalloc(sizeof(u32) * imx->master.num_chipselect);
 
 	for (i = 0; i < imx->master.num_chipselect; i++)
diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
index 821a95980f..0d7407c279 100644
--- a/drivers/spi/stm32_spi.c
+++ b/drivers/spi/stm32_spi.c
@@ -514,7 +514,7 @@ static void stm32_spi_dt_probe(struct stm32_spi_priv *priv)
 	struct device_node *node = priv->master.dev->of_node;
 	int i;
 
-	priv->master.num_chipselect = of_gpio_named_count(node, "cs-gpios");
+	priv->master.num_chipselect = of_gpio_count_csgpios(node);
 	priv->cs_gpios = xzalloc(sizeof(u32) * priv->master.num_chipselect);
 
 	for (i = 0; i < priv->master.num_chipselect; i++)
diff --git a/include/of_gpio.h b/include/of_gpio.h
index 30ff204baf..794a9926cd 100644
--- a/include/of_gpio.h
+++ b/include/of_gpio.h
@@ -69,6 +69,23 @@ static inline int of_gpio_count(struct device_node *np)
 	return of_gpio_named_count(np, "gpios");
 }
 
+/**
+ * of_gpio_count() - Count cs-gpios for a device
+ * @np:		device node to count cs-gpios for
+ *
+ * Same as of_gpio_named_count, but hard coded to use the 'cs-gpios' property
+ * Returns 0 on error
+ */
+static inline int of_gpio_count_csgpios(struct device_node *np)
+{
+	int count = of_gpio_named_count(np, "cs-gpios");
+
+	if (count > 0)
+		return count;
+	else
+		return 0;
+}
+
 static inline int of_get_gpio_flags(struct device_node *np, int index,
 		      enum of_gpio_flags *flags)
 {
-- 
2.39.0