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

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Message-ID: <20231012035838.2804064-3-chris.packham@alliedtelesis.co.nz>
Date:   Thu, 12 Oct 2023 16:58:38 +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 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>
---
 drivers/i2c/busses/i2c-mv64xxx.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index efd28bbecf61..b2ca31857cbd 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 = {
@@ -1083,6 +1084,10 @@ 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 PTR_ERR(drv_data->reset_gpio);
+
 	if (pdata) {
 		drv_data->freq_m = pdata->freq_m;
 		drv_data->freq_n = pdata->freq_n;
@@ -1121,6 +1126,12 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 			goto exit_disable_pm;
 	}
 
+	if (drv_data->reset_gpio) {
+		udelay(1);
+		gpiod_set_value_cansleep(drv_data->reset_gpio, 0);
+		udelay(1);
+	}
+
 	rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
 			 MV64XXX_I2C_CTLR_NAME, drv_data);
 	if (rc) {
-- 
2.42.0