usb: typec: mux: Introduce GPIO-based SBU mux

A design found in various Qualcomm-based boards is to use a USB switch,
controlled through a pair of GPIO lines to connect, disconnect and
switch the orientation of the SBU lines in USB Type-C applications.

This introduces a generic driver, which implements the typec_switch and
typec_mux interfaces to perform these operations.

Reviewed-by: Heikki Krogerus <[e-mail]>
Signed-off-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/typec/mux/Kconfig

···
 	  common USB Type-C connector.
 	  If compiled as a module, the module will be named fsa4480.
 
+config TYPEC_MUX_GPIO_SBU
+	tristate "Generic GPIO based SBU mux for USB Type-C applications"
+	help
+	  Say Y or M if your system uses a GPIO based mux for managing the
+	  connected state and the swapping of the SBU lines in a Type-C port.
+
 config TYPEC_MUX_PI3USB30532
 	tristate "Pericom PI3USB30532 Type-C cross switch driver"
 	depends on I2C

drivers/usb/typec/mux/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_TYPEC_MUX_FSA4480)		+= fsa4480.o
+obj-$(CONFIG_TYPEC_MUX_GPIO_SBU)	+= gpio-sbu-mux.o
 obj-$(CONFIG_TYPEC_MUX_PI3USB30532)	+= pi3usb30532.o
 obj-$(CONFIG_TYPEC_MUX_INTEL_PMC)	+= intel_pmc_mux.o

drivers/usb/typec/mux/gpio-sbu-mux.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Linaro Ltd.
+ */
+
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/gpio/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/usb/typec_dp.h>
+#include <linux/usb/typec_mux.h>
+
+struct gpio_sbu_mux {
+	struct gpio_desc *enable_gpio;
+	struct gpio_desc *select_gpio;
+
+	struct typec_switch_dev *sw;
+	struct typec_mux_dev *mux;
+
+	struct mutex lock; /* protect enabled and swapped */
+	bool enabled;
+	bool swapped;
+};
+
+static int gpio_sbu_switch_set(struct typec_switch_dev *sw,
+			       enum typec_orientation orientation)
+{
+	struct gpio_sbu_mux *sbu_mux = typec_switch_get_drvdata(sw);
+	bool enabled;
+	bool swapped;
+
+	mutex_lock(&sbu_mux->lock);
+
+	enabled = sbu_mux->enabled;
+	swapped = sbu_mux->swapped;
+
+	switch (orientation) {
+	case TYPEC_ORIENTATION_NONE:
+		enabled = false;
+		break;
+	case TYPEC_ORIENTATION_NORMAL:
+		swapped = false;
+		break;
+	case TYPEC_ORIENTATION_REVERSE:
+		swapped = true;
+		break;
+	}
+
+	if (enabled != sbu_mux->enabled)
+		gpiod_set_value(sbu_mux->enable_gpio, enabled);
+
+	if (swapped != sbu_mux->swapped)
+		gpiod_set_value(sbu_mux->select_gpio, swapped);
+
+	sbu_mux->enabled = enabled;
+	sbu_mux->swapped = swapped;
+
+	mutex_unlock(&sbu_mux->lock);
+
+	return 0;
+}
+
+static int gpio_sbu_mux_set(struct typec_mux_dev *mux,
+			    struct typec_mux_state *state)
+{
+	struct gpio_sbu_mux *sbu_mux = typec_mux_get_drvdata(mux);
+
+	mutex_lock(&sbu_mux->lock);
+
+	switch (state->mode) {
+	case TYPEC_STATE_SAFE:
+	case TYPEC_STATE_USB:
+		sbu_mux->enabled = false;
+		break;
+	case TYPEC_DP_STATE_C:
+	case TYPEC_DP_STATE_D:
+	case TYPEC_DP_STATE_E:
+		sbu_mux->enabled = true;
+		break;
+	default:
+		break;
+	}
+
+	gpiod_set_value(sbu_mux->enable_gpio, sbu_mux->enabled);
+
+	mutex_unlock(&sbu_mux->lock);
+
+	return 0;
+}
+
+static int gpio_sbu_mux_probe(struct platform_device *pdev)
+{
+	struct typec_switch_desc sw_desc = { };
+	struct typec_mux_desc mux_desc = { };
+	struct device *dev = &pdev->dev;
+	struct gpio_sbu_mux *sbu_mux;
+
+	sbu_mux = devm_kzalloc(dev, sizeof(*sbu_mux), GFP_KERNEL);
+	if (!sbu_mux)
+		return -ENOMEM;
+
+	mutex_init(&sbu_mux->lock);
+
+	sbu_mux->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(sbu_mux->enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(sbu_mux->enable_gpio),
+				     "unable to acquire enable gpio\n");
+
+	sbu_mux->select_gpio = devm_gpiod_get(dev, "select", GPIOD_OUT_LOW);
+	if (IS_ERR(sbu_mux->select_gpio))
+		return dev_err_probe(dev, PTR_ERR(sbu_mux->select_gpio),
+				     "unable to acquire select gpio\n");
+
+	sw_desc.drvdata = sbu_mux;
+	sw_desc.fwnode = dev_fwnode(dev);
+	sw_desc.set = gpio_sbu_switch_set;
+
+	sbu_mux->sw = typec_switch_register(dev, &sw_desc);
+	if (IS_ERR(sbu_mux->sw))
+		return dev_err_probe(dev, PTR_ERR(sbu_mux->sw),
+				     "failed to register typec switch\n");
+
+	mux_desc.drvdata = sbu_mux;
+	mux_desc.fwnode = dev_fwnode(dev);
+	mux_desc.set = gpio_sbu_mux_set;
+
+	sbu_mux->mux = typec_mux_register(dev, &mux_desc);
+	if (IS_ERR(sbu_mux->mux)) {
+		typec_switch_unregister(sbu_mux->sw);
+		return dev_err_probe(dev, PTR_ERR(sbu_mux->mux),
+				     "failed to register typec mux\n");
+	}
+
+	platform_set_drvdata(pdev, sbu_mux);
+
+	return 0;
+}
+
+static int gpio_sbu_mux_remove(struct platform_device *pdev)
+{
+	struct gpio_sbu_mux *sbu_mux = platform_get_drvdata(pdev);
+
+	gpiod_set_value(sbu_mux->enable_gpio, 0);
+
+	typec_mux_unregister(sbu_mux->mux);
+	typec_switch_unregister(sbu_mux->sw);
+
+	return 0;
+}
+
+static const struct of_device_id gpio_sbu_mux_match[] = {
+	{ .compatible = "gpio-sbu-mux", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, gpio_sbu_mux_match);
+
+static struct platform_driver gpio_sbu_mux_driver = {
+	.probe = gpio_sbu_mux_probe,
+	.remove = gpio_sbu_mux_remove,
+	.driver = {
+		.name = "gpio_sbu_mux",
+		.of_match_table = gpio_sbu_mux_match,
+	},
+};
+module_platform_driver(gpio_sbu_mux_driver);
+
+MODULE_DESCRIPTION("GPIO based SBU mux driver");
+MODULE_LICENSE("GPL");