linux-kernel - [PATCH v2 2/2] i2c: mv64xxx: add an optional reset-gpios property

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Date:   Mon, 16 Oct 2023 15:35:04 +1300
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     gregory.clement@...tlin.com, andi.shyti@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org
Cc:     linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v2 2/2] i2c: mv64xxx: add an optional reset-gpios property

Some hardware designs have a GPIO used to control the reset of all the
devices on and I2C bus. It's not possible for every child node to
declare a reset-gpios property as only the first device probed would be
able to successfully request it (the others will get -EBUSY). Represent
this kind of hardware design by associating the reset-gpios with the
parent I2C bus. The reset line will be released prior to the child I2C
devices being probed.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---

Notes:
    Changes in v2:
    - Add a property to cover the length of delay after releasing the reset
      GPIO
    - Use dev_err_probe() when requesing the GPIO fails

 drivers/i2c/busses/i2c-mv64xxx.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index efd28bbecf61..50c470e5c4be 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -160,6 +160,7 @@ struct mv64xxx_i2c_data {
 	bool			clk_n_base_0;
 	struct i2c_bus_recovery_info	rinfo;
 	bool			atomic;
+	struct gpio_desc	*reset_gpio;
 };
 
 static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx = {
@@ -1036,6 +1037,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	struct mv64xxx_i2c_data		*drv_data;
 	struct mv64xxx_i2c_pdata	*pdata = dev_get_platdata(&pd->dev);
 	struct resource *res;
+	u32	reset_udelay;
 	int	rc;
 
 	if ((!pdata && !pd->dev.of_node))
@@ -1083,6 +1085,14 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	if (drv_data->irq < 0)
 		return drv_data->irq;
 
+	drv_data->reset_gpio = devm_gpiod_get_optional(&pd->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(drv_data->reset_gpio))
+		return dev_err_probe(&pd->dev, PTR_ERR(drv_data->reset_gpio),
+				     "Cannot get reset gpio\n");
+	rc = device_property_read_u32(&pd->dev, "reset-delay-us", &reset_udelay);
+	if (rc)
+		reset_udelay = 1;
+
 	if (pdata) {
 		drv_data->freq_m = pdata->freq_m;
 		drv_data->freq_n = pdata->freq_n;
@@ -1121,6 +1131,11 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 			goto exit_disable_pm;
 	}
 
+	if (drv_data->reset_gpio) {
+		gpiod_set_value_cansleep(drv_data->reset_gpio, 0);
+		usleep_range(reset_udelay, reset_udelay + 10);
+	}
+
 	rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
 			 MV64XXX_I2C_CTLR_NAME, drv_data);
 	if (rc) {
-- 
2.42.0