cdx: add the cdx bus driver

Introduce AMD CDX bus, which provides a mechanism for scanning
and probing CDX devices. These devices are memory mapped on
system bus for Application Processors(APUs).

CDX devices can be changed dynamically in the Fabric and CDX
bus interacts with CDX controller to rescan the bus and
rediscover the devices.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Tested-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
Link: https://lore.kernel.org/r/20230313132636.31850-2-nipun.gupta@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

6 files changed, 498 insertions, 0 deletions

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 968bd0a6fd78..514ae6b24cb2 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -241,4 +241,6 @@ source "drivers/peci/Kconfig"
 
 source "drivers/hte/Kconfig"
 
+source "drivers/cdx/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 20b118dca999..7241d80a7b29 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -194,3 +194,4 @@ obj-$(CONFIG_MOST)		+= most/
 obj-$(CONFIG_PECI)		+= peci/
 obj-$(CONFIG_HTE)		+= hte/
 obj-$(CONFIG_DRM_ACCEL)		+= accel/
+obj-$(CONFIG_CDX_BUS)		+= cdx/
diff --git a/drivers/cdx/Kconfig b/drivers/cdx/Kconfig
new file mode 100644
index 000000000000..1aaee0ec5bd9
--- /dev/null
+++ b/drivers/cdx/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# CDX bus configuration
+#
+# Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+#
+
+config CDX_BUS
+	bool "CDX Bus driver"
+	depends on OF && ARM64
+	help
+	  Driver to enable Composable DMA Transfer(CDX) Bus. CDX bus
+	  exposes Fabric devices which uses composable DMA IP to the
+	  APU. CDX bus provides a mechanism for scanning and probing
+	  of CDX devices. CDX devices are memory mapped on system bus
+	  for embedded CPUs. CDX bus uses CDX controller and firmware
+	  to scan these CDX devices.
diff --git a/drivers/cdx/Makefile b/drivers/cdx/Makefile
new file mode 100644
index 000000000000..c5feb11fc718
--- /dev/null
+++ b/drivers/cdx/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for CDX
+#
+# Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+#
+
+obj-$(CONFIG_CDX_BUS) += cdx.o
diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
new file mode 100644
index 000000000000..6b162bbb9b25
--- /dev/null
+++ b/drivers/cdx/cdx.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CDX bus driver.
+ *
+ * Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+ */
+
+/*
+ * Architecture Overview
+ * =====================
+ * CDX is a Hardware Architecture designed for AMD FPGA devices. It
+ * consists of sophisticated mechanism for interaction between FPGA,
+ * Firmware and the APUs (Application CPUs).
+ *
+ * Firmware resides on RPU (Realtime CPUs) which interacts with
+ * the FPGA program manager and the APUs. The RPU provides memory-mapped
+ * interface (RPU if) which is used to communicate with APUs.
+ *
+ * The diagram below shows an overview of the CDX architecture:
+ *
+ *          +--------------------------------------+
+ *          |    Application CPUs (APU)            |
+ *          |                                      |
+ *          |                    CDX device drivers|
+ *          |     Linux OS                |        |
+ *          |                        CDX bus       |
+ *          |                             |        |
+ *          |                     CDX controller   |
+ *          |                             |        |
+ *          +-----------------------------|--------+
+ *                                        | (discover, config,
+ *                                        |  reset, rescan)
+ *                                        |
+ *          +------------------------| RPU if |----+
+ *          |                             |        |
+ *          |                             V        |
+ *          |          Realtime CPUs (RPU)         |
+ *          |                                      |
+ *          +--------------------------------------+
+ *                                |
+ *          +---------------------|----------------+
+ *          |  FPGA               |                |
+ *          |      +-----------------------+       |
+ *          |      |           |           |       |
+ *          | +-------+    +-------+   +-------+   |
+ *          | | dev 1 |    | dev 2 |   | dev 3 |   |
+ *          | +-------+    +-------+   +-------+   |
+ *          +--------------------------------------+
+ *
+ * The RPU firmware extracts the device information from the loaded FPGA
+ * image and implements a mechanism that allows the APU drivers to
+ * enumerate such devices (device personality and resource details) via
+ * a dedicated communication channel. RPU mediates operations such as
+ * discover, reset and rescan of the FPGA devices for the APU. This is
+ * done using memory mapped interface provided by the RPU to APU.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/of_device.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/xarray.h>
+#include <linux/cdx/cdx_bus.h>
+#include "cdx.h"
+
+/* Default DMA mask for devices on a CDX bus */
+#define CDX_DEFAULT_DMA_MASK	(~0ULL)
+#define MAX_CDX_CONTROLLERS 16
+
+/* CDX controllers registered with the CDX bus */
+static DEFINE_XARRAY_ALLOC(cdx_controllers);
+
+/**
+ * cdx_unregister_device - Unregister a CDX device
+ * @dev: CDX device
+ * @data: This is always passed as NULL, and is not used in this API,
+ *	  but is required here as the bus_for_each_dev() API expects
+ *	  the passed function (cdx_unregister_device) to have this
+ *	  as an argument.
+ *
+ * Return: 0 on success.
+ */
+static int cdx_unregister_device(struct device *dev,
+				 void *data)
+{
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+
+	kfree(cdx_dev->driver_override);
+	cdx_dev->driver_override = NULL;
+	/*
+	 * Do not free cdx_dev here as it would be freed in
+	 * cdx_device_release() called from within put_device().
+	 */
+	device_del(&cdx_dev->dev);
+	put_device(&cdx_dev->dev);
+
+	return 0;
+}
+
+static void cdx_unregister_devices(struct bus_type *bus)
+{
+	/* Reset all the devices attached to cdx bus */
+	bus_for_each_dev(bus, NULL, NULL, cdx_unregister_device);
+}
+
+/**
+ * cdx_match_one_device - Tell if a CDX device structure has a matching
+ *			  CDX device id structure
+ * @id: single CDX device id structure to match
+ * @dev: the CDX device structure to match against
+ *
+ * Return: matching cdx_device_id structure or NULL if there is no match.
+ */
+static inline const struct cdx_device_id *
+cdx_match_one_device(const struct cdx_device_id *id,
+		     const struct cdx_device *dev)
+{
+	/* Use vendor ID and device ID for matching */
+	if ((id->vendor == CDX_ANY_ID || id->vendor == dev->vendor) &&
+	    (id->device == CDX_ANY_ID || id->device == dev->device))
+		return id;
+	return NULL;
+}
+
+/**
+ * cdx_match_id - See if a CDX device matches a given cdx_id table
+ * @ids: array of CDX device ID structures to search in
+ * @dev: the CDX device structure to match against.
+ *
+ * Used by a driver to check whether a CDX device is in its list of
+ * supported devices. Returns the matching cdx_device_id structure or
+ * NULL if there is no match.
+ *
+ * Return: matching cdx_device_id structure or NULL if there is no match.
+ */
+static inline const struct cdx_device_id *
+cdx_match_id(const struct cdx_device_id *ids, struct cdx_device *dev)
+{
+	if (ids) {
+		while (ids->vendor || ids->device) {
+			if (cdx_match_one_device(ids, dev))
+				return ids;
+			ids++;
+		}
+	}
+	return NULL;
+}
+
+/**
+ * cdx_bus_match - device to driver matching callback
+ * @dev: the cdx device to match against
+ * @drv: the device driver to search for matching cdx device
+ * structures
+ *
+ * Return: true on success, false otherwise.
+ */
+static int cdx_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+	struct cdx_driver *cdx_drv = to_cdx_driver(drv);
+	const struct cdx_device_id *found_id = NULL;
+	const struct cdx_device_id *ids;
+
+	ids = cdx_drv->match_id_table;
+
+	/* When driver_override is set, only bind to the matching driver */
+	if (cdx_dev->driver_override && strcmp(cdx_dev->driver_override, drv->name))
+		return false;
+
+	found_id = cdx_match_id(ids, cdx_dev);
+	if (!found_id)
+		return false;
+
+	do {
+		/*
+		 * In case override_only was set, enforce driver_override
+		 * matching.
+		 */
+		if (!found_id->override_only)
+			return true;
+		if (cdx_dev->driver_override)
+			return true;
+
+		ids = found_id + 1;
+		found_id = cdx_match_id(ids, cdx_dev);
+	} while (found_id);
+
+	return false;
+}
+
+static int cdx_probe(struct device *dev)
+{
+	struct cdx_driver *cdx_drv = to_cdx_driver(dev->driver);
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+	int error;
+
+	error = cdx_drv->probe(cdx_dev);
+	if (error) {
+		dev_err_probe(dev, error, "%s failed\n", __func__);
+		return error;
+	}
+
+	return 0;
+}
+
+static void cdx_remove(struct device *dev)
+{
+	struct cdx_driver *cdx_drv = to_cdx_driver(dev->driver);
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+
+	if (cdx_drv && cdx_drv->remove)
+		cdx_drv->remove(cdx_dev);
+}
+
+static void cdx_shutdown(struct device *dev)
+{
+	struct cdx_driver *cdx_drv = to_cdx_driver(dev->driver);
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+
+	if (cdx_drv && cdx_drv->shutdown)
+		cdx_drv->shutdown(cdx_dev);
+}
+
+static int cdx_dma_configure(struct device *dev)
+{
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+	u32 input_id = cdx_dev->req_id;
+	int ret;
+
+	ret = of_dma_configure_id(dev, dev->parent->of_node, 0, &input_id);
+	if (ret && ret != -EPROBE_DEFER) {
+		dev_err(dev, "of_dma_configure_id() failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static ssize_t rescan_store(struct bus_type *bus,
+			    const char *buf, size_t count)
+{
+	struct cdx_controller *cdx;
+	unsigned long index;
+	bool val;
+
+	if (kstrtobool(buf, &val) < 0)
+		return -EINVAL;
+
+	if (!val)
+		return -EINVAL;
+
+	/* Unregister all the devices on the bus */
+	cdx_unregister_devices(&cdx_bus_type);
+
+	/* Rescan all the devices */
+	xa_for_each(&cdx_controllers, index, cdx) {
+		int ret;
+
+		ret = cdx->ops->scan(cdx);
+		if (ret)
+			dev_err(cdx->dev, "cdx bus scanning failed\n");
+	}
+
+	return count;
+}
+static BUS_ATTR_WO(rescan);
+
+static struct attribute *cdx_bus_attrs[] = {
+	&bus_attr_rescan.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cdx_bus);
+
+struct bus_type cdx_bus_type = {
+	.name		= "cdx",
+	.match		= cdx_bus_match,
+	.probe		= cdx_probe,
+	.remove		= cdx_remove,
+	.shutdown	= cdx_shutdown,
+	.dma_configure	= cdx_dma_configure,
+	.bus_groups	= cdx_bus_groups,
+};
+EXPORT_SYMBOL_GPL(cdx_bus_type);
+
+int __cdx_driver_register(struct cdx_driver *cdx_driver,
+			  struct module *owner)
+{
+	int error;
+
+	cdx_driver->driver.owner = owner;
+	cdx_driver->driver.bus = &cdx_bus_type;
+
+	error = driver_register(&cdx_driver->driver);
+	if (error) {
+		pr_err("driver_register() failed for %s: %d\n",
+		       cdx_driver->driver.name, error);
+		return error;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__cdx_driver_register);
+
+void cdx_driver_unregister(struct cdx_driver *cdx_driver)
+{
+	driver_unregister(&cdx_driver->driver);
+}
+EXPORT_SYMBOL_GPL(cdx_driver_unregister);
+
+static void cdx_device_release(struct device *dev)
+{
+	struct cdx_device *cdx_dev = to_cdx_device(dev);
+
+	kfree(cdx_dev);
+}
+
+int cdx_device_add(struct cdx_dev_params *dev_params)
+{
+	struct cdx_controller *cdx = dev_params->cdx;
+	struct device *parent = cdx->dev;
+	struct cdx_device *cdx_dev;
+	int ret;
+
+	cdx_dev = kzalloc(sizeof(*cdx_dev), GFP_KERNEL);
+	if (!cdx_dev)
+		return -ENOMEM;
+
+	/* Populate resource */
+	memcpy(cdx_dev->res, dev_params->res, sizeof(struct resource) *
+		dev_params->res_count);
+	cdx_dev->res_count = dev_params->res_count;
+
+	/* Populate CDX dev params */
+	cdx_dev->req_id = dev_params->req_id;
+	cdx_dev->vendor = dev_params->vendor;
+	cdx_dev->device = dev_params->device;
+	cdx_dev->bus_num = dev_params->bus_num;
+	cdx_dev->dev_num = dev_params->dev_num;
+	cdx_dev->cdx = dev_params->cdx;
+	cdx_dev->dma_mask = CDX_DEFAULT_DMA_MASK;
+
+	/* Initialize generic device */
+	device_initialize(&cdx_dev->dev);
+	cdx_dev->dev.parent = parent;
+	cdx_dev->dev.bus = &cdx_bus_type;
+	cdx_dev->dev.dma_mask = &cdx_dev->dma_mask;
+	cdx_dev->dev.release = cdx_device_release;
+
+	/* Set Name */
+	dev_set_name(&cdx_dev->dev, "cdx-%02x:%02x",
+		     ((cdx->id << CDX_CONTROLLER_ID_SHIFT) | (cdx_dev->bus_num & CDX_BUS_NUM_MASK)),
+		     cdx_dev->dev_num);
+
+	ret = device_add(&cdx_dev->dev);
+	if (ret) {
+		dev_err(&cdx_dev->dev,
+			"cdx device add failed: %d", ret);
+		goto fail;
+	}
+
+	return 0;
+fail:
+	/*
+	 * Do not free cdx_dev here as it would be freed in
+	 * cdx_device_release() called from put_device().
+	 */
+	put_device(&cdx_dev->dev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cdx_device_add);
+
+int cdx_register_controller(struct cdx_controller *cdx)
+{
+	int ret;
+
+	ret = xa_alloc(&cdx_controllers, &cdx->id, cdx,
+		       XA_LIMIT(0, MAX_CDX_CONTROLLERS - 1), GFP_KERNEL);
+	if (ret) {
+		dev_err(cdx->dev,
+			"No free index available. Maximum controllers already registered\n");
+		cdx->id = (u8)MAX_CDX_CONTROLLERS;
+		return ret;
+	}
+
+	/* Scan all the devices */
+	cdx->ops->scan(cdx);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cdx_register_controller);
+
+void cdx_unregister_controller(struct cdx_controller *cdx)
+{
+	if (cdx->id >= MAX_CDX_CONTROLLERS)
+		return;
+
+	device_for_each_child(cdx->dev, NULL, cdx_unregister_device);
+	xa_erase(&cdx_controllers, cdx->id);
+}
+EXPORT_SYMBOL_GPL(cdx_unregister_controller);
+
+static int __init cdx_bus_init(void)
+{
+	return bus_register(&cdx_bus_type);
+}
+postcore_initcall(cdx_bus_init);
diff --git a/drivers/cdx/cdx.h b/drivers/cdx/cdx.h
new file mode 100644
index 000000000000..c436ac7ac86f
--- /dev/null
+++ b/drivers/cdx/cdx.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Header file for the CDX Bus
+ *
+ * Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+ */
+
+#ifndef _CDX_H_
+#define _CDX_H_
+
+#include <linux/cdx/cdx_bus.h>
+
+/**
+ * struct cdx_dev_params - CDX device parameters
+ * @cdx: CDX controller associated with the device
+ * @parent: Associated CDX controller
+ * @vendor: Vendor ID for CDX device
+ * @device: Device ID for CDX device
+ * @bus_num: Bus number for this CDX device
+ * @dev_num: Device number for this device
+ * @res: array of MMIO region entries
+ * @res_count: number of valid MMIO regions
+ * @req_id: Requestor ID associated with CDX device
+ */
+struct cdx_dev_params {
+	struct cdx_controller *cdx;
+	u16 vendor;
+	u16 device;
+	u8 bus_num;
+	u8 dev_num;
+	struct resource res[MAX_CDX_DEV_RESOURCES];
+	u8 res_count;
+	u32 req_id;
+};
+
+/**
+ * cdx_register_controller - Register a CDX controller and its ports
+ *		on the CDX bus.
+ * @cdx: The CDX controller to register
+ *
+ * Return: -errno on failure, 0 on success.
+ */
+int cdx_register_controller(struct cdx_controller *cdx);
+
+/**
+ * cdx_unregister_controller - Unregister a CDX controller
+ * @cdx: The CDX controller to unregister
+ */
+void cdx_unregister_controller(struct cdx_controller *cdx);
+
+/**
+ * cdx_device_add - Add a CDX device. This function adds a CDX device
+ *		on the CDX bus as per the device parameters provided
+ *		by caller. It also creates and registers an associated
+ *		Linux generic device.
+ * @dev_params: device parameters associated with the device to be created.
+ *
+ * Return: -errno on failure, 0 on success.
+ */
+int cdx_device_add(struct cdx_dev_params *dev_params);
+
+#endif /* _CDX_H_ */