usb: add bus type for USB ULPI

UTMI+ Low Pin Interface (ULPI) is a commonly used PHY
interface for USB 2.0. The ULPI specification describes a
standard set of registers which the vendors can extend for
their specific needs. ULPI PHYs provide often functions
such as charger detection and ADP sensing and probing.

There are two major issues that the bus type is meant to
tackle:

Firstly, ULPI registers are accessed from the controller.
The bus provides convenient method for the controller
drivers to share that access with the actual PHY drivers.

Secondly, there are already platforms that assume ULPI PHYs
are runtime detected, such as many Intel Baytrail based
platforms. They do not provide any kind of hardware
description for the ULPI PHYs like separate ACPI device
object that could be used to enumerate a device from.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

3 files changed, 276 insertions, 0 deletions

diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index ca2f8bd0e431..6bbb3ec17018 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -7,3 +7,4 @@ usb-common-y			  += common.o
 usb-common-$(CONFIG_USB_LED_TRIG) += led.o
 
 obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
+obj-$(CONFIG_USB_ULPI_BUS)	+= ulpi.o
diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
new file mode 100644
index 000000000000..0e6f968e93fe
--- /dev/null
+++ b/drivers/usb/common/ulpi.c
@@ -0,0 +1,255 @@
+/**
+ * ulpi.c - USB ULPI PHY bus
+ *
+ * Copyright (C) 2015 Intel Corporation
+ *
+ * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/ulpi/interface.h>
+#include <linux/ulpi/driver.h>
+#include <linux/ulpi/regs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/acpi.h>
+
+/* -------------------------------------------------------------------------- */
+
+int ulpi_read(struct ulpi *ulpi, u8 addr)
+{
+	return ulpi->ops->read(ulpi->ops, addr);
+}
+EXPORT_SYMBOL_GPL(ulpi_read);
+
+int ulpi_write(struct ulpi *ulpi, u8 addr, u8 val)
+{
+	return ulpi->ops->write(ulpi->ops, addr, val);
+}
+EXPORT_SYMBOL_GPL(ulpi_write);
+
+/* -------------------------------------------------------------------------- */
+
+static int ulpi_match(struct device *dev, struct device_driver *driver)
+{
+	struct ulpi_driver *drv = to_ulpi_driver(driver);
+	struct ulpi *ulpi = to_ulpi_dev(dev);
+	const struct ulpi_device_id *id;
+
+	for (id = drv->id_table; id->vendor; id++)
+		if (id->vendor == ulpi->id.vendor &&
+		    id->product == ulpi->id.product)
+			return 1;
+
+	return 0;
+}
+
+static int ulpi_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct ulpi *ulpi = to_ulpi_dev(dev);
+
+	if (add_uevent_var(env, "MODALIAS=ulpi:v%04xp%04x",
+			   ulpi->id.vendor, ulpi->id.product))
+		return -ENOMEM;
+	return 0;
+}
+
+static int ulpi_probe(struct device *dev)
+{
+	struct ulpi_driver *drv = to_ulpi_driver(dev->driver);
+
+	return drv->probe(to_ulpi_dev(dev));
+}
+
+static int ulpi_remove(struct device *dev)
+{
+	struct ulpi_driver *drv = to_ulpi_driver(dev->driver);
+
+	if (drv->remove)
+		drv->remove(to_ulpi_dev(dev));
+
+	return 0;
+}
+
+static struct bus_type ulpi_bus = {
+	.name = "ulpi",
+	.match = ulpi_match,
+	.uevent = ulpi_uevent,
+	.probe = ulpi_probe,
+	.remove = ulpi_remove,
+};
+
+/* -------------------------------------------------------------------------- */
+
+static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct ulpi *ulpi = to_ulpi_dev(dev);
+
+	return sprintf(buf, "ulpi:v%04xp%04x\n",
+		       ulpi->id.vendor, ulpi->id.product);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static struct attribute *ulpi_dev_attrs[] = {
+	&dev_attr_modalias.attr,
+	NULL
+};
+
+static struct attribute_group ulpi_dev_attr_group = {
+	.attrs = ulpi_dev_attrs,
+};
+
+static const struct attribute_group *ulpi_dev_attr_groups[] = {
+	&ulpi_dev_attr_group,
+	NULL
+};
+
+static void ulpi_dev_release(struct device *dev)
+{
+	kfree(to_ulpi_dev(dev));
+}
+
+static struct device_type ulpi_dev_type = {
+	.name = "ulpi_device",
+	.groups = ulpi_dev_attr_groups,
+	.release = ulpi_dev_release,
+};
+
+/* -------------------------------------------------------------------------- */
+
+/**
+ * ulpi_register_driver - register a driver with the ULPI bus
+ * @drv: driver being registered
+ *
+ * Registers a driver with the ULPI bus.
+ */
+int ulpi_register_driver(struct ulpi_driver *drv)
+{
+	if (!drv->probe)
+		return -EINVAL;
+
+	drv->driver.bus = &ulpi_bus;
+
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(ulpi_register_driver);
+
+/**
+ * ulpi_unregister_driver - unregister a driver with the ULPI bus
+ * @drv: driver to unregister
+ *
+ * Unregisters a driver with the ULPI bus.
+ */
+void ulpi_unregister_driver(struct ulpi_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(ulpi_unregister_driver);
+
+/* -------------------------------------------------------------------------- */
+
+static int ulpi_register(struct device *dev, struct ulpi *ulpi)
+{
+	int ret;
+
+	/* Test the interface */
+	ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
+	if (ret < 0)
+		return ret;
+
+	ret = ulpi_read(ulpi, ULPI_SCRATCH);
+	if (ret < 0)
+		return ret;
+
+	if (ret != 0xaa)
+		return -ENODEV;
+
+	ulpi->id.vendor = ulpi_read(ulpi, ULPI_VENDOR_ID_LOW);
+	ulpi->id.vendor |= ulpi_read(ulpi, ULPI_VENDOR_ID_HIGH) << 8;
+
+	ulpi->id.product = ulpi_read(ulpi, ULPI_PRODUCT_ID_LOW);
+	ulpi->id.product |= ulpi_read(ulpi, ULPI_PRODUCT_ID_HIGH) << 8;
+
+	ulpi->dev.parent = dev;
+	ulpi->dev.bus = &ulpi_bus;
+	ulpi->dev.type = &ulpi_dev_type;
+	dev_set_name(&ulpi->dev, "%s.ulpi", dev_name(dev));
+
+	ACPI_COMPANION_SET(&ulpi->dev, ACPI_COMPANION(dev));
+
+	request_module("ulpi:v%04xp%04x", ulpi->id.vendor, ulpi->id.product);
+
+	ret = device_register(&ulpi->dev);
+	if (ret)
+		return ret;
+
+	dev_dbg(&ulpi->dev, "registered ULPI PHY: vendor %04x, product %04x\n",
+		ulpi->id.vendor, ulpi->id.product);
+
+	return 0;
+}
+
+/**
+ * ulpi_register_interface - instantiate new ULPI device
+ * @dev: USB controller's device interface
+ * @ops: ULPI register access
+ *
+ * Allocates and registers a ULPI device and an interface for it. Called from
+ * the USB controller that provides the ULPI interface.
+ */
+struct ulpi *ulpi_register_interface(struct device *dev, struct ulpi_ops *ops)
+{
+	struct ulpi *ulpi;
+	int ret;
+
+	ulpi = kzalloc(sizeof(*ulpi), GFP_KERNEL);
+	if (!ulpi)
+		return ERR_PTR(-ENOMEM);
+
+	ulpi->ops = ops;
+	ops->dev = dev;
+
+	ret = ulpi_register(dev, ulpi);
+	if (ret) {
+		kfree(ulpi);
+		return ERR_PTR(ret);
+	}
+
+	return ulpi;
+}
+EXPORT_SYMBOL_GPL(ulpi_register_interface);
+
+/**
+ * ulpi_unregister_interface - unregister ULPI interface
+ * @intrf: struct ulpi_interface
+ *
+ * Unregisters a ULPI device and it's interface that was created with
+ * ulpi_create_interface().
+ */
+void ulpi_unregister_interface(struct ulpi *ulpi)
+{
+	device_unregister(&ulpi->dev);
+}
+EXPORT_SYMBOL_GPL(ulpi_unregister_interface);
+
+/* -------------------------------------------------------------------------- */
+
+static int __init ulpi_init(void)
+{
+	return bus_register(&ulpi_bus);
+}
+module_init(ulpi_init);
+
+static void __exit ulpi_exit(void)
+{
+	bus_unregister(&ulpi_bus);
+}
+module_exit(ulpi_exit);
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("USB ULPI PHY bus");
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index cc0ced08bae2..a99c89e78126 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -84,3 +84,23 @@ config USB_OTG_FSM
 	  Implements OTG Finite State Machine as specified in On-The-Go
 	  and Embedded Host Supplement to the USB Revision 2.0 Specification.
 
+config USB_ULPI_BUS
+	tristate "USB ULPI PHY interface support"
+	depends on USB_SUPPORT
+	help
+	  UTMI+ Low Pin Interface (ULPI) is specification for a commonly used
+	  USB 2.0 PHY interface. The ULPI specification defines a standard set
+	  of registers that can be used to detect the vendor and product which
+	  allows ULPI to be handled as a bus. This module is the driver for that
+	  bus.
+
+	  The ULPI interfaces (the buses) are registered by the drivers for USB
+	  controllers which support ULPI register access and have ULPI PHY
+	  attached to them. The ULPI PHY drivers themselves are normal PHY
+	  drivers.
+
+	  ULPI PHYs provide often functions such as ADP sensing/probing (OTG
+	  protocol) and USB charger detection.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called ulpi.