peci: Add support for PECI bus driver core

This commit adds driver implementation for PECI bus core into linux
driver framework.

PECI (Platform Environment Control Interface) is a one-wire bus interface
that provides a communication channel from Intel processors and chipset
components to external monitoring or control devices. PECI is designed to
support the following sideband functions:

* Processor and DRAM thermal management
  - Processor fan speed control is managed by comparing Digital Thermal
    Sensor (DTS) thermal readings acquired via PECI against the
    processor-specific fan speed control reference point, or TCONTROL. Both
    TCONTROL and DTS thermal readings are accessible via the processor PECI
    client. These variables are referenced to a common temperature, the TCC
    activation point, and are both defined as negative offsets from that
    reference.
  - PECI based access to the processor package configuration space provides
    a means for Baseboard Management Controllers (BMC) or other platform
    management devices to actively manage the processor and memory power
    and thermal features.

* Platform Manageability
  - Platform manageability functions including thermal, power, and error
    monitoring. Note that platform 'power' management includes monitoring
    and control for both the processor and DRAM subsystem to assist with
    data center power limiting.
  - PECI allows read access to certain error registers in the processor MSR
    space and status monitoring registers in the PCI configuration space
    within the processor and downstream devices.
  - PECI permits writes to certain registers in the processor PCI
    configuration space.

* Processor Interface Tuning and Diagnostics
  - Processor interface tuning and diagnostics capabilities
    (Intel Interconnect BIST). The processors Intel Interconnect Built In
    Self Test (Intel IBIST) allows for infield diagnostic capabilities in
    the Intel UPI and memory controller interfaces. PECI provides a port to
    execute these diagnostics via its PCI Configuration read and write
    capabilities.

* Failure Analysis
  - Output the state of the processor after a failure for analysis via
    Crashdump.

PECI uses a single wire for self-clocking and data transfer. The bus
requires no additional control lines. The physical layer is a self-clocked
one-wire bus that begins each bit with a driven, rising edge from an idle
level near zero volts. The duration of the signal driven high depends on
whether the bit value is a logic '0' or logic '1'. PECI also includes
variable data transfer rate established with every message. In this way, it
is highly flexible even though underlying logic is simple.

The interface design was optimized for interfacing between an Intel
processor and chipset components in both single processor and multiple
processor environments. The single wire interface provides low board
routing overhead for the multiple load connections in the congested routing
area near the processor and chipset components. Bus speed, error checking,
and low protocol overhead provides adequate link bandwidth and reliability
to transfer critical device operating conditions and configuration
information.

This implementation provides the basic framework to add PECI extensions to
the Linux bus and device models. A hardware specific 'Adapter' driver can
be attached to the PECI bus to provide sideband functions described above.
It is also possible to access all devices on an adapter from userspace
through the /dev interface. A device specific 'Client' driver also can be
attached to the PECI bus so each processor client's features can be
supported by the 'Client' driver through an adapter connection in the bus.

Signed-off-by: Jason M Biils <jason.m.bills@linux.intel.com>
Signed-off-by: Yunge Zhu <yunge.zhu@linux.intel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Reviewed-by: James Feist <james.feist@linux.intel.com>
Reviewed-by: Vernon Mauery <vernon.mauery@linux.intel.com>

1 files changed, 150 insertions, 0 deletions

diff --git a/include/linux/peci.h b/include/linux/peci.h
new file mode 100644
index 000000000000..4bc4595c797d
--- /dev/null
+++ b/include/linux/peci.h
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2018-2019 Intel Corporation */
+
+#ifndef __LINUX_PECI_H
+#define __LINUX_PECI_H
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/peci-ioctl.h>
+
+#define PECI_NAME_SIZE   32
+
+struct peci_board_info {
+	char			type[PECI_NAME_SIZE];
+	u8			addr;	/* CPU client address */
+	struct device_node	*of_node;
+};
+
+/**
+ * struct peci_adapter - represent a PECI adapter
+ * @owner: owner module of the PECI adpater
+ * @bus_lock: mutex for exclusion of multiple callers
+ * @dev: device interface to this driver
+ * @nr: the bus number to map
+ * @name: name of the adapter
+ * @userspace_clients_lock: mutex for exclusion of clients handling
+ * @userspace_clients: list of registered clients
+ * @xfer: low-level transfer function pointer of the adapter
+ * @cmd_mask: mask for supportable PECI commands
+ * @use_dma: flag for indicating that adapter uses DMA
+ *
+ * Each PECI adapter can communicate with one or more PECI client children.
+ * These make a small bus, sharing a single wired PECI connection.
+ */
+struct peci_adapter {
+	struct module		*owner;
+	struct mutex		bus_lock; /* mutex for bus locking */
+	struct device		dev;
+	int			nr;
+	char			name[PECI_NAME_SIZE];
+	struct mutex		userspace_clients_lock; /* clients list mutex */
+	struct list_head	userspace_clients;
+	int			(*xfer)(struct peci_adapter *adapter,
+					struct peci_xfer_msg *msg);
+	u32			cmd_mask;
+	bool			use_dma;
+};
+
+static inline struct peci_adapter *to_peci_adapter(void *d)
+{
+	return container_of(d, struct peci_adapter, dev);
+}
+
+static inline void *peci_get_adapdata(const struct peci_adapter *adapter)
+{
+	return dev_get_drvdata(&adapter->dev);
+}
+
+static inline void peci_set_adapdata(struct peci_adapter *adapter, void *data)
+{
+	dev_set_drvdata(&adapter->dev, data);
+}
+
+/**
+ * struct peci_client - represent a PECI client device
+ * @dev: driver model device node for the client
+ * @adapter: manages the bus segment hosting this PECI device
+ * @addr: address used on the PECI bus connected to the parent adapter
+ * @name: indicates the type of the device
+ * @detected: detected PECI clients list
+ *
+ * A peci_client identifies a single device (i.e. CPU) connected to a peci bus.
+ * The behaviour exposed to Linux is defined by the driver managing the device.
+ */
+struct peci_client {
+	struct device		dev;
+	struct peci_adapter	*adapter;
+	u8			addr;
+	char			name[PECI_NAME_SIZE];
+	struct list_head	detected;
+};
+
+static inline struct peci_client *to_peci_client(void *d)
+{
+	return container_of(d, struct peci_client, dev);
+}
+
+struct peci_device_id {
+	char	name[PECI_NAME_SIZE];
+	ulong	driver_data;	/* Data private to the driver */
+};
+
+/**
+ * struct peci_driver - represent a PECI device driver
+ * @probe: callback for device binding
+ * @remove: callback for device unbinding
+ * @shutdown: callback for device shutdown
+ * @driver: device driver model driver
+ * @id_table: list of PECI devices supported by this driver
+ *
+ * The driver.owner field should be set to the module owner of this driver.
+ * The driver.name field should be set to the name of this driver.
+ */
+struct peci_driver {
+	int				(*probe)(struct peci_client *client);
+	int				(*remove)(struct peci_client *client);
+	void				(*shutdown)(struct peci_client *client);
+	struct device_driver		driver;
+	const struct peci_device_id	*id_table;
+};
+
+static inline struct peci_driver *to_peci_driver(void *d)
+{
+	return container_of(d, struct peci_driver, driver);
+}
+
+/**
+ * module_peci_driver - Helper macro for registering a modular PECI driver
+ * @__peci_driver: peci_driver struct
+ *
+ * Helper macro for PECI drivers which do not do anything special in module
+ * init/exit. This eliminates a lot of boilerplate. Each module may only
+ * use this macro once, and calling it replaces module_init() and module_exit()
+ */
+#define module_peci_driver(__peci_driver) \
+	module_driver(__peci_driver, peci_add_driver, peci_del_driver)
+
+/* use a define to avoid include chaining to get THIS_MODULE */
+#define peci_add_driver(driver) peci_register_driver(THIS_MODULE, driver)
+
+extern struct bus_type peci_bus_type;
+extern struct device_type peci_adapter_type;
+extern struct device_type peci_client_type;
+
+int  peci_register_driver(struct module *owner, struct peci_driver *drv);
+void peci_del_driver(struct peci_driver *driver);
+struct peci_client *peci_verify_client(struct device *dev);
+struct peci_adapter *peci_alloc_adapter(struct device *dev, uint size);
+struct peci_adapter *peci_get_adapter(int nr);
+void peci_put_adapter(struct peci_adapter *adapter);
+int  peci_add_adapter(struct peci_adapter *adapter);
+void peci_del_adapter(struct peci_adapter *adapter);
+struct peci_adapter *peci_verify_adapter(struct device *dev);
+int  peci_for_each_dev(void *data, int (*fn)(struct device *, void *));
+struct peci_xfer_msg *peci_get_xfer_msg(u8 tx_len, u8 rx_len);
+void peci_put_xfer_msg(struct peci_xfer_msg *msg);
+int  peci_command(struct peci_adapter *adpater, enum peci_cmd cmd, void *vmsg);
+int  peci_get_cpu_id(struct peci_adapter *adapter, u8 addr, u32 *cpu_id);
+
+#endif /* __LINUX_PECI_H */