1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * xen-acpi-pad.c - Xen pad interface
  4 *
  5 * Copyright (c) 2012, Intel Corporation.
  6 *    Author: Liu, Jinsong <jinsong.liu@intel.com>
  7 */
  8
  9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 10
 11#include <linux/kernel.h>
 12#include <linux/types.h>
 13#include <linux/acpi.h>
 14#include <xen/xen.h>
 15#include <xen/interface/version.h>
 16#include <xen/xen-ops.h>
 17#include <asm/xen/hypercall.h>
 18
 19#define ACPI_PROCESSOR_AGGREGATOR_CLASS	"acpi_pad"
 20#define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
 21#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
 22static DEFINE_MUTEX(xen_cpu_lock);
 23
 24static int xen_acpi_pad_idle_cpus(unsigned int idle_nums)
 25{
 26	struct xen_platform_op op;
 27
 28	op.cmd = XENPF_core_parking;
 29	op.u.core_parking.type = XEN_CORE_PARKING_SET;
 30	op.u.core_parking.idle_nums = idle_nums;
 31
 32	return HYPERVISOR_platform_op(&op);
 33}
 34
 35static int xen_acpi_pad_idle_cpus_num(void)
 36{
 37	struct xen_platform_op op;
 38
 39	op.cmd = XENPF_core_parking;
 40	op.u.core_parking.type = XEN_CORE_PARKING_GET;
 41
 42	return HYPERVISOR_platform_op(&op)
 43	       ?: op.u.core_parking.idle_nums;
 44}
 45
 46/*
 47 * Query firmware how many CPUs should be idle
 48 * return -1 on failure
 49 */
 50static int acpi_pad_pur(acpi_handle handle)
 51{
 52	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
 53	union acpi_object *package;
 54	int num = -1;
 55
 56	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
 57		return num;
 58
 59	if (!buffer.length || !buffer.pointer)
 60		return num;
 61
 62	package = buffer.pointer;
 63
 64	if (package->type == ACPI_TYPE_PACKAGE &&
 65		package->package.count == 2 &&
 66		package->package.elements[0].integer.value == 1) /* rev 1 */
 67		num = package->package.elements[1].integer.value;
 68
 69	kfree(buffer.pointer);
 70	return num;
 71}
 72
 73static void acpi_pad_handle_notify(acpi_handle handle)
 74{
 75	int idle_nums;
 76	struct acpi_buffer param = {
 77		.length = 4,
 78		.pointer = (void *)&idle_nums,
 79	};
 80
 81
 82	mutex_lock(&xen_cpu_lock);
 83	idle_nums = acpi_pad_pur(handle);
 84	if (idle_nums < 0) {
 85		mutex_unlock(&xen_cpu_lock);
 86		return;
 87	}
 88
 89	idle_nums = xen_acpi_pad_idle_cpus(idle_nums)
 90		    ?: xen_acpi_pad_idle_cpus_num();
 91	if (idle_nums >= 0)
 92		acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY,
 93				  0, &param);
 94	mutex_unlock(&xen_cpu_lock);
 95}
 96
 97static void acpi_pad_notify(acpi_handle handle, u32 event,
 98	void *data)
 99{
100	switch (event) {
101	case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
102		acpi_pad_handle_notify(handle);
103		break;
104	default:
105		pr_warn("Unsupported event [0x%x]\n", event);
106		break;
107	}
108}
109
110static int acpi_pad_add(struct acpi_device *device)
111{
112	acpi_status status;
113
114	strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
115	strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
116
117	status = acpi_install_notify_handler(device->handle,
118		ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
119	if (ACPI_FAILURE(status))
120		return -ENODEV;
121
122	return 0;
123}
124
125static void acpi_pad_remove(struct acpi_device *device)
126{
127	mutex_lock(&xen_cpu_lock);
128	xen_acpi_pad_idle_cpus(0);
129	mutex_unlock(&xen_cpu_lock);
130
131	acpi_remove_notify_handler(device->handle,
132		ACPI_DEVICE_NOTIFY, acpi_pad_notify);
133}
134
135static const struct acpi_device_id pad_device_ids[] = {
136	{"ACPI000C", 0},
137	{"", 0},
138};
139
140static struct acpi_driver acpi_pad_driver = {
141	.name = "processor_aggregator",
142	.class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
143	.ids = pad_device_ids,
144	.ops = {
145		.add = acpi_pad_add,
146		.remove = acpi_pad_remove,
147	},
148};
149
150static int __init xen_acpi_pad_init(void)
151{
152	/* Only DOM0 is responsible for Xen acpi pad */
153	if (!xen_initial_domain())
154		return -ENODEV;
155
156	/* Only Xen4.2 or later support Xen acpi pad */
157	if (!xen_running_on_version_or_later(4, 2))
158		return -ENODEV;
159
160	return acpi_bus_register_driver(&acpi_pad_driver);
161}
162subsys_initcall(xen_acpi_pad_init);