linux-kernel - [PATCH v4] i2c: muxes: pca954x: Allow sharing reset GPIO

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Message-ID: <20240312201400.716009-1-chris.packham@alliedtelesis.co.nz>
Date: Wed, 13 Mar 2024 09:14:00 +1300
From: Chris Packham <chris.packham@...iedtelesis.co.nz>
To: peda@...ntia.se,
	p.zabel@...gutronix.de,
	krzysztof.kozlowski@...aro.org
Cc: linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v4] i2c: muxes: pca954x: Allow sharing reset GPIO

Some hardware designs with multiple PCA954x devices use a reset GPIO
connected to all the muxes. Support this configuration by making use of
the reset controller framework which can deal with the shared reset
GPIOs. Fall back to the old GPIO descriptor method if the reset
controller framework is not enabled.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
Acked-by: Peter Rosin <peda@...ntia.se>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---

Notes:
    This patch goes on top of Krzysztof's series adding the GPIO based reset
    controller[1] which will be in linux-6.9. With this I'm able to
    correctly describe my hardware platform in the DTS and have the resets
    appropriately controlled.
    
    [1] - https://lore.kernel.org/all/20240129115216.96479-1-krzysztof.kozlowski@linaro.org/
    
    I caused a bit of confusion and send this as a new patch without any
    reference to the earlier versions. It is a bit complicated as I sent v1
    which Krzysztof included in v3 of his series but then dropped before the
    series landed. The content hasn't changed since v1 but tags have been
    added in the latest version.
    
    Changes in v4:
    - Add Ack and R-by from Peter and Krzysztof
    
    v3 resend: https://lore.kernel.org/all/20240311041412.3858710-1-chrispackham@alliedtelesis.co.nz/
    
    v3: https://lore.kernel.org/lkml/20240112163608.528453-6-krzysztof.kozlowski@linaro.org/
    
    v1: https://lore.kernel.org/all/20240108041913.7078-1-chris.packham@alliedtelesis.co.nz/

 drivers/i2c/muxes/i2c-mux-pca954x.c | 46 ++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index f5dfc33b97c0..c3f4ff08ac38 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -49,6 +49,7 @@
 #include <linux/pm.h>
 #include <linux/property.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <dt-bindings/mux/mux.h>
@@ -116,6 +117,9 @@ struct pca954x {
 	unsigned int irq_mask;
 	raw_spinlock_t lock;
 	struct regulator *supply;
+
+	struct gpio_desc *reset_gpio;
+	struct reset_control *reset_cont;
 };
 
 /* Provide specs for the MAX735x, PCA954x and PCA984x types we know about */
@@ -518,6 +522,35 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data)
 	return ret;
 }
 
+static int pca954x_get_reset(struct device *dev, struct pca954x *data)
+{
+	data->reset_cont = devm_reset_control_get_optional_shared(dev, NULL);
+	if (IS_ERR(data->reset_cont))
+		return dev_err_probe(dev, PTR_ERR(data->reset_cont),
+				     "Failed to get reset\n");
+	else if (data->reset_cont)
+		return 0;
+
+	/*
+	 * fallback to legacy reset-gpios
+	 */
+	data->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(data->reset_gpio)) {
+		return dev_err_probe(dev, PTR_ERR(data->reset_gpio),
+				     "Failed to get reset gpio");
+	}
+
+	return 0;
+}
+
+static void pca954x_reset_deassert(struct pca954x *data)
+{
+	if (data->reset_cont)
+		reset_control_deassert(data->reset_cont);
+	else
+		gpiod_set_value_cansleep(data->reset_gpio, 0);
+}
+
 /*
  * I2C init/probing/exit functions
  */
@@ -526,7 +559,6 @@ static int pca954x_probe(struct i2c_client *client)
 	const struct i2c_device_id *id = i2c_client_get_device_id(client);
 	struct i2c_adapter *adap = client->adapter;
 	struct device *dev = &client->dev;
-	struct gpio_desc *gpio;
 	struct i2c_mux_core *muxc;
 	struct pca954x *data;
 	int num;
@@ -554,15 +586,13 @@ static int pca954x_probe(struct i2c_client *client)
 		return dev_err_probe(dev, ret,
 				     "Failed to enable vdd supply\n");
 
-	/* Reset the mux if a reset GPIO is specified. */
-	gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
-	if (IS_ERR(gpio)) {
-		ret = PTR_ERR(gpio);
+	ret = pca954x_get_reset(dev, data);
+	if (ret)
 		goto fail_cleanup;
-	}
-	if (gpio) {
+
+	if (data->reset_cont || data->reset_gpio) {
 		udelay(1);
-		gpiod_set_value_cansleep(gpio, 0);
+		pca954x_reset_deassert(data);
 		/* Give the chip some time to recover. */
 		udelay(1);
 	}
-- 
2.43.2