gpiolib: Support 'gpio-reserved-ranges' property

Some qcom platforms make some GPIOs or pins unavailable for use by
non-secure operating systems, and thus reading or writing the registers
for those pins will cause access control issues. Add support for a DT
property to describe the set of GPIOs that are available for use so that
higher level OSes are able to know what pins to avoid reading/writing.
Non-DT platforms can add support by directly updating the
chip->valid_mask.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Timur Tabi <timur@codeaurora.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 84e5a9df2344..ed81d9a6316f 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -511,6 +511,28 @@ void of_mm_gpiochip_remove(struct of_mm_gpio_chip *mm_gc)
 }
 EXPORT_SYMBOL(of_mm_gpiochip_remove);
 
+static void of_gpiochip_init_valid_mask(struct gpio_chip *chip)
+{
+	int len, i;
+	u32 start, count;
+	struct device_node *np = chip->of_node;
+
+	len = of_property_count_u32_elems(np,  "gpio-reserved-ranges");
+	if (len < 0 || len % 2 != 0)
+		return;
+
+	for (i = 0; i < len; i += 2) {
+		of_property_read_u32_index(np, "gpio-reserved-ranges",
+					   i, &start);
+		of_property_read_u32_index(np, "gpio-reserved-ranges",
+					   i + 1, &count);
+		if (start >= chip->ngpio || start + count >= chip->ngpio)
+			continue;
+
+		bitmap_clear(chip->valid_mask, start, count);
+	}
+};
+
 #ifdef CONFIG_PINCTRL
 static int of_gpiochip_add_pin_range(struct gpio_chip *chip)
 {
@@ -615,6 +637,8 @@ int of_gpiochip_add(struct gpio_chip *chip)
 	if (chip->of_gpio_n_cells > MAX_PHANDLE_ARGS)
 		return -EINVAL;
 
+	of_gpiochip_init_valid_mask(chip);
+
 	status = of_gpiochip_add_pin_range(chip);
 	if (status)
 		return status;