Merge branch 'net-pse-pd-tps23881-reset-gpio-support'

Kyle Swenson says:

====================
net: pse-pd: tps23881: Reset GPIO support

On some boards, the TPS2388x's reset line (active low) is pulled low to
keep the chip in reset until the SoC pulls the device out of reset.
This series updates the device-tree binding for the tps23881 and then
adds support for the reset gpio handling in the tps23881 driver.

v1: https://lore.kernel.org/20240819190151.93253-1-kyle.swenson@est.tech
====================

Link: https://patch.msgid.link/20240822220100.3030184-1-kyle.swenson@est.tech
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/pse-pd/ti,tps23881.yaml

@@ -23,6 +23,9 @@ properties:
   '#pse-cells':
     const: 1
 
+  reset-gpios:
+    maxItems: 1
+
   channels:
     description: each set of 8 ports can be assigned to one physical
       channels or two for PoE4. This parameter describes the configuration

drivers/net/pse-pd/tps23881.c

@@ -8,6 +8,7 @@
 #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>
@@ -737,6 +738,7 @@ 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;
 
@@ -749,6 +751,25 @@ static int tps23881_i2c_probe(struct i2c_client *client)
 	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;