gpio: of: Handle the Freescale SPI CS

The Freescale SPI chipselects are special: while everyone else
is using "cs-gpios" the Freescale platforms just use "gpios".
Fix this by responding with "gpios" when asking for "cs-gpios"
in a freescale device node, so we hide this pecularity from
the SPI core.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib-of.c

@@ -254,6 +254,37 @@ static struct gpio_desc *of_find_spi_gpio(struct device *dev, const char *con_id
 	return desc;
 }
 
+/*
+ * The old Freescale bindings use simply "gpios" as name for the chip select
+ * lines rather than "cs-gpios" like all other SPI hardware. Account for this
+ * with a special quirk.
+ */
+static struct gpio_desc *of_find_spi_cs_gpio(struct device *dev,
+					     const char *con_id,
+					     unsigned int idx,
+					     unsigned long *flags)
+{
+	struct device_node *np = dev->of_node;
+
+	if (!IS_ENABLED(CONFIG_SPI_MASTER))
+		return ERR_PTR(-ENOENT);
+
+	/* Allow this specifically for Freescale devices */
+	if (!of_device_is_compatible(np, "fsl,spi") &&
+	    !of_device_is_compatible(np, "aeroflexgaisler,spictrl"))
+		return ERR_PTR(-ENOENT);
+	/* Allow only if asking for "cs-gpios" */
+	if (!con_id || strcmp(con_id, "cs"))
+		return ERR_PTR(-ENOENT);
+
+	/*
+	 * While all other SPI controllers use "cs-gpios" the Freescale
+	 * uses just "gpios" so translate to that when "cs-gpios" is
+	 * requested.
+	 */
+	return of_find_gpio(dev, NULL, idx, flags);
+}
+
 /*
  * Some regulator bindings happened before we managed to establish that GPIO
  * properties should be named "foo-gpios" so we have this special kludge for
@@ -325,6 +356,12 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 	/* Special handling for SPI GPIOs if used */
 	if (IS_ERR(desc))
 		desc = of_find_spi_gpio(dev, con_id, &of_flags);
+	if (IS_ERR(desc)) {
+		/* This quirk looks up flags and all */
+		desc = of_find_spi_cs_gpio(dev, con_id, idx, flags);
+		if (!IS_ERR(desc))
+			return desc;
+	}
 
 	/* Special handling for regulator GPIOs if used */
 	if (IS_ERR(desc) && PTR_ERR(desc) != -EPROBE_DEFER)