i3c: Add core I3C infrastructure

Add core infrastructure to support I3C in Linux and document it.

This infrastructure adds basic I3C support. Advanced features will be
added afterwards.

There are a few design choices that are worth mentioning because they
impact the way I3C device drivers can interact with their devices:

- all functions used to send I3C/I2C frames must be called in
  non-atomic context. Mainly done this way to ease implementation, but
  this is not set in stone, and if anyone needs async support, new
  functions can be added later on.
- the bus element is a separate object, but it's tightly coupled with
  the master object. We thus have a 1:1 relationship between i3c_bus
  and i3c_master_controller objects, and if 2 master controllers are
  connected to the same bus and both exposed to the same Linux instance
  they will appear as two distinct busses, and devices on this bus will
  be exposed twice.
- I2C backward compatibility has been designed to be transparent to I2C
  drivers and the I2C subsystem. The I3C master just registers an I2C
  adapter which creates a new I2C bus. I'd say that, from a
  representation PoV it's not ideal because what should appear as a
  single I3C bus exposing I3C and I2C devices here appears as 2
  different buses connected to each other through the parenting (the
  I3C master is the parent of the I2C and I3C busses).
  On the other hand, I don't see a better solution if we want something
  that is not invasive.

Missing features:
- I3C HDR modes are not supported
- no support for multi-master and the associated concepts (mastership
  handover, support for secondary masters, ...)
- I2C devices can only be described using DT because this is the only
  use case I have. However, the framework can easily be extended with
  ACPI and board info support
- I3C slave framework. This has been completely omitted, but shouldn't
  have a huge impact on the I3C framework because I3C slaves don't see
  the whole bus, it's only about handling master requests and generating
  IBIs. Some of the struct, constant and enum definitions could be
  shared, but most of the I3C slave framework logic will be different
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/Kconfig

@@ -57,6 +57,8 @@ source "drivers/char/Kconfig"
 
 source "drivers/i2c/Kconfig"
 
+source "drivers/i3c/Kconfig"
+
 source "drivers/spi/Kconfig"
 
 source "drivers/spmi/Kconfig"

drivers/Makefile

@@ -111,7 +111,7 @@ obj-$(CONFIG_SERIO)		+= input/serio/
 obj-$(CONFIG_GAMEPORT)		+= input/gameport/
 obj-$(CONFIG_INPUT)		+= input/
 obj-$(CONFIG_RTC_LIB)		+= rtc/
-obj-y				+= i2c/ media/
+obj-y				+= i2c/ i3c/ media/
 obj-$(CONFIG_PPS)		+= pps/
 obj-y				+= ptp/
 obj-$(CONFIG_W1)		+= w1/

drivers/i3c/Kconfig

+# SPDX-License-Identifier: GPL-2.0
+
+menuconfig I3C
+	tristate "I3C support"
+	select I2C
+	help
+	  I3C is a serial protocol standardized by the MIPI alliance.
+
+	  It's supposed to be backward compatible with I2C while providing
+	  support for high speed transfers and native interrupt support
+	  without the need for extra pins.
+
+	  The I3C protocol also standardizes the slave device types and is
+	  mainly designed to communicate with sensors.
+
+	  If you want I3C support, you should say Y here and also to the
+	  specific driver for your bus adapter(s) below.
+
+	  This I3C support can also be built as a module.  If so, the module
+	  will be called i3c.
+
+if I3C
+source "drivers/i3c/master/Kconfig"
+endif # I3C

drivers/i3c/Makefile

+# SPDX-License-Identifier: GPL-2.0
+i3c-y				:= device.o master.o
+obj-$(CONFIG_I3C)		+= i3c.o
+obj-$(CONFIG_I3C)		+= master/

drivers/i3c/device.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Cadence Design Systems Inc.
+ *
+ * Author: Boris Brezillon <boris.brezillon@bootlin.com>
+ */
+
+#include <linux/atomic.h>
+#include <linux/bug.h>
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+
+#include "internals.h"
+
+/**
+ * i3c_device_do_priv_xfers() - do I3C SDR private transfers directed to a
+ *				specific device
+ *
+ * @dev: device with which the transfers should be done
+ * @xfers: array of transfers
+ * @nxfers: number of transfers
+ *
+ * Initiate one or several private SDR transfers with @dev.
+ *
+ * This function can sleep and thus cannot be called in atomic context.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+int i3c_device_do_priv_xfers(struct i3c_device *dev,
+			     struct i3c_priv_xfer *xfers,
+			     int nxfers)
+{
+	int ret, i;
+
+	if (nxfers < 1)
+		return 0;
+
+	for (i = 0; i < nxfers; i++) {
+		if (!xfers[i].len || !xfers[i].data.in)
+			return -EINVAL;
+	}
+
+	i3c_bus_normaluse_lock(dev->bus);
+	ret = i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers);
+	i3c_bus_normaluse_unlock(dev->bus);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i3c_device_do_priv_xfers);
+
+/**
+ * i3c_device_get_info() - get I3C device information
+ *
+ * @dev: device we want information on
+ * @info: the information object to fill in
+ *
+ * Retrieve I3C dev info.
+ */
+void i3c_device_get_info(struct i3c_device *dev,
+			 struct i3c_device_info *info)
+{
+	if (!info)
+		return;
+
+	i3c_bus_normaluse_lock(dev->bus);
+	if (dev->desc)
+		*info = dev->desc->info;
+	i3c_bus_normaluse_unlock(dev->bus);
+}
+EXPORT_SYMBOL_GPL(i3c_device_get_info);
+
+/**
+ * i3c_device_disable_ibi() - Disable IBIs coming from a specific device
+ * @dev: device on which IBIs should be disabled
+ *
+ * This function disable IBIs coming from a specific device and wait for
+ * all pending IBIs to be processed.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+int i3c_device_disable_ibi(struct i3c_device *dev)
+{
+	int ret = -ENOENT;
+
+	i3c_bus_normaluse_lock(dev->bus);
+	if (dev->desc) {
+		mutex_lock(&dev->desc->ibi_lock);
+		ret = i3c_dev_disable_ibi_locked(dev->desc);
+		mutex_unlock(&dev->desc->ibi_lock);
+	}
+	i3c_bus_normaluse_unlock(dev->bus);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i3c_device_disable_ibi);
+
+/**
+ * i3c_device_enable_ibi() - Enable IBIs coming from a specific device
+ * @dev: device on which IBIs should be enabled
+ *
+ * This function enable IBIs coming from a specific device and wait for
+ * all pending IBIs to be processed. This should be called on a device
+ * where i3c_device_request_ibi() has succeeded.
+ *
+ * Note that IBIs from this device might be received before this function
+ * returns to its caller.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+int i3c_device_enable_ibi(struct i3c_device *dev)
+{
+	int ret = -ENOENT;
+
+	i3c_bus_normaluse_lock(dev->bus);
+	if (dev->desc) {
+		mutex_lock(&dev->desc->ibi_lock);
+		ret = i3c_dev_enable_ibi_locked(dev->desc);
+		mutex_unlock(&dev->desc->ibi_lock);
+	}
+	i3c_bus_normaluse_unlock(dev->bus);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i3c_device_enable_ibi);
+
+/**
+ * i3c_device_request_ibi() - Request an IBI
+ * @dev: device for which we should enable IBIs
+ * @req: setup requested for this IBI
+ *
+ * This function is responsible for pre-allocating all resources needed to
+ * process IBIs coming from @dev. When this function returns, the IBI is not
+ * enabled until i3c_device_enable_ibi() is called.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+int i3c_device_request_ibi(struct i3c_device *dev,
+			   const struct i3c_ibi_setup *req)
+{
+	int ret = -ENOENT;
+
+	if (!req->handler || !req->num_slots)
+		return -EINVAL;
+
+	i3c_bus_normaluse_lock(dev->bus);
+	if (dev->desc) {
+		mutex_lock(&dev->desc->ibi_lock);
+		ret = i3c_dev_request_ibi_locked(dev->desc, req);
+		mutex_unlock(&dev->desc->ibi_lock);
+	}
+	i3c_bus_normaluse_unlock(dev->bus);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i3c_device_request_ibi);
+
+/**
+ * i3c_device_free_ibi() - Free all resources needed for IBI handling
+ * @dev: device on which you want to release IBI resources
+ *
+ * This function is responsible for de-allocating resources previously
+ * allocated by i3c_device_request_ibi(). It should be called after disabling
+ * IBIs with i3c_device_disable_ibi().
+ */
+void i3c_device_free_ibi(struct i3c_device *dev)
+{
+	i3c_bus_normaluse_lock(dev->bus);
+	if (dev->desc) {
+		mutex_lock(&dev->desc->ibi_lock);
+		i3c_dev_free_ibi_locked(dev->desc);
+		mutex_unlock(&dev->desc->ibi_lock);
+	}
+	i3c_bus_normaluse_unlock(dev->bus);
+}
+EXPORT_SYMBOL_GPL(i3c_device_free_ibi);
+
+/**
+ * i3cdev_to_dev() - Returns the device embedded in @i3cdev
+ * @i3cdev: I3C device
+ *
+ * Return: a pointer to a device object.
+ */
+struct device *i3cdev_to_dev(struct i3c_device *i3cdev)
+{
+	return &i3cdev->dev;
+}
+EXPORT_SYMBOL_GPL(i3cdev_to_dev);
+
+/**
+ * dev_to_i3cdev() - Returns the I3C device containing @dev
+ * @dev: device object
+ *
+ * Return: a pointer to an I3C device object.
+ */
+struct i3c_device *dev_to_i3cdev(struct device *dev)
+{
+	return container_of(dev, struct i3c_device, dev);
+}
+EXPORT_SYMBOL_GPL(dev_to_i3cdev);
+
+/**
+ * i3c_driver_register_with_owner() - register an I3C device driver
+ *
+ * @drv: driver to register
+ * @owner: module that owns this driver
+ *
+ * Register @drv to the core.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+int i3c_driver_register_with_owner(struct i3c_driver *drv, struct module *owner)
+{
+	drv->driver.owner = owner;
+	drv->driver.bus = &i3c_bus_type;
+
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(i3c_driver_register_with_owner);
+
+/**
+ * i3c_driver_unregister() - unregister an I3C device driver
+ *
+ * @drv: driver to unregister
+ *
+ * Unregister @drv.
+ */
+void i3c_driver_unregister(struct i3c_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(i3c_driver_unregister);

drivers/i3c/internals.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 Cadence Design Systems Inc.
+ *
+ * Author: Boris Brezillon <boris.brezillon@bootlin.com>
+ */
+
+#ifndef I3C_INTERNALS_H
+#define I3C_INTERNALS_H
+
+#include <linux/i3c/master.h>
+
+extern struct bus_type i3c_bus_type;
+
+void i3c_bus_normaluse_lock(struct i3c_bus *bus);
+void i3c_bus_normaluse_unlock(struct i3c_bus *bus);
+
+int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
+				 struct i3c_priv_xfer *xfers,
+				 int nxfers);
+int i3c_dev_disable_ibi_locked(struct i3c_dev_desc *dev);
+int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
+int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
+			       const struct i3c_ibi_setup *req);
+void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);
+#endif /* I3C_INTERNAL_H */

include/linux/mod_devicetable.h

@@ -448,6 +448,23 @@ struct pci_epf_device_id {
 	kernel_ulong_t driver_data;
 };
 
+/* i3c */
+
+#define I3C_MATCH_DCR			0x1
+#define I3C_MATCH_MANUF			0x2
+#define I3C_MATCH_PART			0x4
+#define I3C_MATCH_EXTRA_INFO		0x8
+
+struct i3c_device_id {
+	__u8 match_flags;
+	__u8 dcr;
+	__u16 manuf_id;
+	__u16 part_id;
+	__u16 extra_info;
+
+	const void *data;
+};
+
 /* spi */
 
 #define SPI_NAME_SIZE	32