gnss: ubx: add support for the safeboot gpio

U-Blox M8/M9 chip have a pin to start it in safeboot mode, to be used
to recover from situations where the flash content has become
corrupted and needs to be restored. If this pin is asserted at power
up/reset, the receiver starts in safeboot mode and GNSS operation is
disabled.

Deassert the safeboot pin when probing this driver.

Signed-off-by: Alejandro Enrique <alejandroe1@geotab.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250911-ubx-safeboot-v3-2-32fe6b882a3c@geotab.com
[ johan: deassert after requesting supplies ]
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/gnss/ubx.c b/drivers/gnss/ubx.c
index 92402f6082c415c7b9051338eef5406b09e09455..23894ff75ff91810650918db35acc53f9c30b050 100644 (file)
--- a/drivers/gnss/ubx.c
+++ b/drivers/gnss/ubx.c
@@ -66,6 +66,7 @@ static const struct gnss_serial_ops ubx_gserial_ops = {
 static int ubx_probe(struct serdev_device *serdev)
 {
        struct gnss_serial *gserial;
+       struct gpio_desc *safeboot;
        struct gpio_desc *reset;
        struct ubx_data *data;
        int ret;
@@ -92,6 +93,13 @@ static int ubx_probe(struct serdev_device *serdev)
        if (ret < 0 && ret != -ENODEV)
                goto err_free_gserial;
 
+       /* Deassert safeboot */
+       safeboot = devm_gpiod_get_optional(&serdev->dev, "safeboot", GPIOD_OUT_LOW);
+       if (IS_ERR(safeboot)) {
+               ret = PTR_ERR(safeboot);
+               goto err_free_gserial;
+       }
+
        /* Deassert reset */
        reset = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_LOW);
        if (IS_ERR(reset)) {