linux-kernel - [PATCH v5 3/3] gnss: ubx: add support for the reset gpio

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Date:   Sun, 12 Nov 2023 19:51:51 -0500
From:   Wolfram Sang <wsa+renesas@...g-engineering.com>
To:     linux-renesas-soc@...r.kernel.org
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v5 3/3] gnss: ubx: add support for the reset gpio

The Renesas KingFisher board includes a U-Blox Neo-M8 chip. This chip
has a reset pin which is also wired on the board. When Linux starts,
reset is asserted by the firmware. Deassert the reset pin when probing
this driver.

Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
Changes since v4:

* don't touch reset during open/close. Only deassert it during probe.

 drivers/gnss/ubx.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gnss/ubx.c b/drivers/gnss/ubx.c
index 9b76b101ba5e..84cb50670644 100644
--- a/drivers/gnss/ubx.c
+++ b/drivers/gnss/ubx.c
@@ -7,6 +7,7 @@
 
 #include <linux/errno.h>
 #include <linux/gnss.h>
+#include <linux/gpio/consumer.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -64,6 +65,7 @@ static const struct gnss_serial_ops ubx_gserial_ops = {
 
 static int ubx_probe(struct serdev_device *serdev)
 {
+	struct gpio_desc *reset_gpio;
 	struct gnss_serial *gserial;
 	struct ubx_data *data;
 	int ret;
@@ -90,6 +92,13 @@ static int ubx_probe(struct serdev_device *serdev)
 	if (ret < 0 && ret != -ENODEV)
 		goto err_free_gserial;
 
+	/* Deassert Reset */
+	reset_gpio = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio)) {
+		ret = PTR_ERR(reset_gpio);
+		goto err_free_gserial;
+	}
+
 	ret = gnss_serial_register(gserial);
 	if (ret)
 		goto err_free_gserial;
-- 
2.35.1