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>

1 files changed, 147 insertions, 0 deletions

diff --git a/include/linux/cdx/cdx_bus.h b/include/linux/cdx/cdx_bus.h
new file mode 100644
index 000000000000..d134e0104724
--- /dev/null
+++ b/include/linux/cdx/cdx_bus.h
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * CDX bus public interface
+ *
+ * Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+ *
+ */
+
+#ifndef _CDX_BUS_H_
+#define _CDX_BUS_H_
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/mod_devicetable.h>
+
+#define MAX_CDX_DEV_RESOURCES	4
+#define CDX_ANY_ID (0xFFFF)
+#define CDX_CONTROLLER_ID_SHIFT 4
+#define CDX_BUS_NUM_MASK 0xF
+
+/* Forward declaration for CDX controller */
+struct cdx_controller;
+
+typedef int (*cdx_scan_cb)(struct cdx_controller *cdx);
+
+/**
+ * CDX_DEVICE_DRIVER_OVERRIDE - macro used to describe a CDX device with
+ *                              override_only flags.
+ * @vend: the 16 bit CDX Vendor ID
+ * @dev: the 16 bit CDX Device ID
+ * @driver_override: the 32 bit CDX Device override_only
+ *
+ * This macro is used to create a struct cdx_device_id that matches only a
+ * driver_override device.
+ */
+#define CDX_DEVICE_DRIVER_OVERRIDE(vend, dev, driver_override) \
+	.vendor = (vend), .device = (dev), .override_only = (driver_override)
+
+/**
+ * struct cdx_ops - Callbacks supported by CDX controller.
+ * @scan: scan the devices on the controller
+ */
+struct cdx_ops {
+	cdx_scan_cb scan;
+};
+
+/**
+ * struct cdx_controller: CDX controller object
+ * @dev: Linux device associated with the CDX controller.
+ * @priv: private data
+ * @id: Controller ID
+ * @ops: CDX controller ops
+ */
+struct cdx_controller {
+	struct device *dev;
+	void *priv;
+	u32 id;
+	struct cdx_ops *ops;
+};
+
+/**
+ * struct cdx_device - CDX device object
+ * @dev: Linux driver model device object
+ * @cdx: CDX controller associated with the device
+ * @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_attr: resource binary attribute
+ * @res_count: number of valid MMIO regions
+ * @dma_mask: Default DMA mask
+ * @flags: CDX device flags
+ * @req_id: Requestor ID associated with CDX device
+ * @driver_override: driver name to force a match; do not set directly,
+ *                   because core frees it; use driver_set_override() to
+ *                   set or clear it.
+ */
+struct cdx_device {
+	struct device dev;
+	struct cdx_controller *cdx;
+	u16 vendor;
+	u16 device;
+	u8 bus_num;
+	u8 dev_num;
+	struct resource res[MAX_CDX_DEV_RESOURCES];
+	u8 res_count;
+	u64 dma_mask;
+	u16 flags;
+	u32 req_id;
+	const char *driver_override;
+};
+
+#define to_cdx_device(_dev) \
+	container_of(_dev, struct cdx_device, dev)
+
+/**
+ * struct cdx_driver - CDX device driver
+ * @driver: Generic device driver
+ * @match_id_table: table of supported device matching Ids
+ * @probe: Function called when a device is added
+ * @remove: Function called when a device is removed
+ * @shutdown: Function called at shutdown time to quiesce the device
+ * @driver_managed_dma: Device driver doesn't use kernel DMA API for DMA.
+ *		For most device drivers, no need to care about this flag
+ *		as long as all DMAs are handled through the kernel DMA API.
+ *		For some special ones, for example VFIO drivers, they know
+ *		how to manage the DMA themselves and set this flag so that
+ *		the IOMMU layer will allow them to setup and manage their
+ *		own I/O address space.
+ */
+struct cdx_driver {
+	struct device_driver driver;
+	const struct cdx_device_id *match_id_table;
+	int (*probe)(struct cdx_device *dev);
+	int (*remove)(struct cdx_device *dev);
+	void (*shutdown)(struct cdx_device *dev);
+	bool driver_managed_dma;
+};
+
+#define to_cdx_driver(_drv) \
+	container_of(_drv, struct cdx_driver, driver)
+
+/* Macro to avoid include chaining to get THIS_MODULE */
+#define cdx_driver_register(drv) \
+	__cdx_driver_register(drv, THIS_MODULE)
+
+/**
+ * __cdx_driver_register - registers a CDX device driver
+ * @cdx_driver: CDX driver to register
+ * @owner: module owner
+ *
+ * Return: -errno on failure, 0 on success.
+ */
+int __must_check __cdx_driver_register(struct cdx_driver *cdx_driver,
+				       struct module *owner);
+
+/**
+ * cdx_driver_unregister - unregisters a device driver from the
+ * CDX bus.
+ * @cdx_driver: CDX driver to register
+ */
+void cdx_driver_unregister(struct cdx_driver *cdx_driver);
+
+extern struct bus_type cdx_bus_type;
+
+#endif /* _CDX_BUS_H_ */