[PATCH net-next v2 2/2] net: pse-pd: tps23881: Support reset-gpios

[Kyle Swenson <kyle.swenson@est.tech>]

The TPS23880/1 has an active-low reset pin that some boards connect to
the SoC to control when the TPS23880 is pulled out of reset.

Add support for this via a reset-gpios property in the DTS.

Signed-off-by: Kyle Swenson <kyle.swenson@est.tech>
---
 drivers/net/pse-pd/tps23881.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/pse-pd/tps23881.c b/drivers/net/pse-pd/tps23881.c
index 2ea75686a319..5c4e88be46ee 100644
--- a/drivers/net/pse-pd/tps23881.c
+++ b/drivers/net/pse-pd/tps23881.c
@@ -6,10 +6,11 @@
  */
 
 #include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/pse-pd/pse.h>
@@ -735,10 +736,11 @@ static int tps23881_flash_sram_fw(struct i2c_client *client)
 
 static int tps23881_i2c_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct tps23881_priv *priv;
+	struct gpio_desc *reset;
 	int ret;
 	u8 val;
 
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 		dev_err(dev, "i2c check functionality failed\n");
@@ -747,10 +749,29 @@ static int tps23881_i2c_probe(struct i2c_client *client)
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
+	reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(reset))
+		return dev_err_probe(&client->dev, PTR_ERR(reset), "Failed to get reset GPIO\n");
+
+	if (reset) {
+		/* TPS23880 datasheet (Rev G) indicates minimum reset pulse is 5us */
+		usleep_range(5, 10);
+		gpiod_set_value_cansleep(reset, 0); /* De-assert reset */
+
+		/* TPS23880 datasheet indicates the minimum time after power on reset
+		 * should be 20ms, but the document describing how to load SRAM ("How
+		 * to Load TPS2388x SRAM and Parity Code over I2C" (Rev E))
+		 * indicates we should delay that programming by at least 50ms. So
+		 * we'll wait the entire 50ms here to ensure we're safe to go to the
+		 * SRAM loading proceedure.
+		 */
+		msleep(50);
+	}
+
 	ret = i2c_smbus_read_byte_data(client, TPS23881_REG_DEVID);
 	if (ret < 0)
 		return ret;
 
 	if (FIELD_GET(TPS23881_REG_DEVID_MASK, ret) != TPS23881_DEVICE_ID) {
-- 
2.43.0