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From:   Naresh Solanki <naresh.solanki@9elements.com>
To:     Patrick Rudolph <patrick.rudolph@9elements.com>,
        Linus Walleij <linus.walleij@linaro.org>
Cc:     Naresh Solanki <Naresh.Solanki@9elements.com>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 2/2] pinctrl: cy8c95x0: Add reset support
Date:   Fri, 14 Jul 2023 10:19:01 +0200
Message-ID: <20230714081902.2621771-2-Naresh.Solanki@9elements.com>
In-Reply-To: <20230714081902.2621771-1-Naresh.Solanki@9elements.com>
References: <20230714081902.2621771-1-Naresh.Solanki@9elements.com>
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From: Patrick Rudolph <patrick.rudolph@9elements.com>

This patch adds support for an optional "reset" GPIO pin in the cy8c95x0
pinctrl driver. On probe, the reset pin is pulled low to bring chip out
of reset. The reset pin has an internal pull-down and can be left
floating if not required.

The datasheet doesn't mention any timing related to the reset pin.

Based on empirical tests, it was found that the chip requires a
delay of 250 milliseconds before accepting I2C transfers after driving
the reset pin low. Therefore, a delay of 250ms is added before
proceeding with I2C transfers.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
---
Changes in V2:
- None
---
 drivers/pinctrl/pinctrl-cy8c95x0.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-cy8c95x0.c b/drivers/pinctrl/pinctrl-cy8c95x0.c
index 2ecc96691c55..58ca6fac7849 100644
--- a/drivers/pinctrl/pinctrl-cy8c95x0.c
+++ b/drivers/pinctrl/pinctrl-cy8c95x0.c
@@ -164,6 +164,7 @@ struct cy8c95x0_pinctrl {
 	struct pinctrl_desc pinctrl_desc;
 	char name[32];
 	unsigned int tpin;
+	struct gpio_desc *gpio_reset;
 };
 
 static const struct pinctrl_pin_desc cy8c9560_pins[] = {
@@ -1383,6 +1384,20 @@ static int cy8c95x0_probe(struct i2c_client *client)
 		chip->regulator = reg;
 	}
 
+	/* bring the chip out of reset if reset pin is provided */
+	chip->gpio_reset = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(chip->gpio_reset)) {
+		ret = dev_err_probe(chip->dev, PTR_ERR(chip->gpio_reset),
+				    "Failed to get GPIO 'reset'\n");
+		goto err_exit;
+	} else if (chip->gpio_reset) {
+		usleep_range(1000, 2000);
+		gpiod_set_value_cansleep(chip->gpio_reset, 0);
+		usleep_range(250000, 300000);
+
+		gpiod_set_consumer_name(chip->gpio_reset, "CY8C95X0 RESET");
+	}
+
 	chip->regmap = devm_regmap_init_i2c(client, &cy8c95x0_i2c_regmap);
 	if (IS_ERR(chip->regmap)) {
 		ret = PTR_ERR(chip->regmap);
-- 
2.41.0