tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Intel Turbo Boost Max Technology 3.0 legacy (non HWP) enumeration driver
3 * Copyright (c) 2017, Intel Corporation.
4 * All rights reserved.
5 *
6 * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms and conditions of the GNU General Public License,
10 * version 2, as published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 */
18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20#include <linux/kernel.h>
21#include <linux/init.h>
22#include <linux/topology.h>
23#include <linux/workqueue.h>
24#include <linux/cpuhotplug.h>
25#include <linux/cpufeature.h>
26#include <asm/cpu_device_id.h>
27#include <asm/intel-family.h>
28
29#define MSR_OC_MAILBOX 0x150
30#define MSR_OC_MAILBOX_CMD_OFFSET 32
31#define MSR_OC_MAILBOX_RSP_OFFSET 32
32#define MSR_OC_MAILBOX_BUSY_BIT 63
33#define OC_MAILBOX_FC_CONTROL_CMD 0x1C
34
35/*
36 * Typical latency to get mail box response is ~3us, It takes +3 us to
37 * process reading mailbox after issuing mailbox write on a Broadwell 3.4 GHz
38 * system. So for most of the time, the first mailbox read should have the
39 * response, but to avoid some boundary cases retry twice.
40 */
41#define OC_MAILBOX_RETRY_COUNT 2
42
43static int get_oc_core_priority(unsigned int cpu)
44{
45 u64 value, cmd = OC_MAILBOX_FC_CONTROL_CMD;
46 int ret, i;
47
48 /* Issue favored core read command */
49 value = cmd << MSR_OC_MAILBOX_CMD_OFFSET;
50 /* Set the busy bit to indicate OS is trying to issue command */
51 value |= BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT);
52 ret = wrmsrl_safe(MSR_OC_MAILBOX, value);
53 if (ret) {
54 pr_debug("cpu %d OC mailbox write failed\n", cpu);
55 return ret;
56 }
57
58 for (i = 0; i < OC_MAILBOX_RETRY_COUNT; ++i) {
59 ret = rdmsrl_safe(MSR_OC_MAILBOX, &value);
60 if (ret) {
61 pr_debug("cpu %d OC mailbox read failed\n", cpu);
62 break;
63 }
64
65 if (value & BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT)) {
66 pr_debug("cpu %d OC mailbox still processing\n", cpu);
67 ret = -EBUSY;
68 continue;
69 }
70
71 if ((value >> MSR_OC_MAILBOX_RSP_OFFSET) & 0xff) {
72 pr_debug("cpu %d OC mailbox cmd failed\n", cpu);
73 ret = -ENXIO;
74 break;
75 }
76
77 ret = value & 0xff;
78 pr_debug("cpu %d max_ratio %d\n", cpu, ret);
79 break;
80 }
81
82 return ret;
83}
84
85/*
86 * The work item is needed to avoid CPU hotplug locking issues. The function
87 * itmt_legacy_set_priority() is called from CPU online callback, so can't
88 * call sched_set_itmt_support() from there as this function will aquire
89 * hotplug locks in its path.
90 */
91static void itmt_legacy_work_fn(struct work_struct *work)
92{
93 sched_set_itmt_support();
94}
95
96static DECLARE_WORK(sched_itmt_work, itmt_legacy_work_fn);
97
98static int itmt_legacy_cpu_online(unsigned int cpu)
99{
100 static u32 max_highest_perf = 0, min_highest_perf = U32_MAX;
101 int priority;
102
103 priority = get_oc_core_priority(cpu);
104 if (priority < 0)
105 return 0;
106
107 sched_set_itmt_core_prio(priority, cpu);
108
109 /* Enable ITMT feature when a core with different priority is found */
110 if (max_highest_perf <= min_highest_perf) {
111 if (priority > max_highest_perf)
112 max_highest_perf = priority;
113
114 if (priority < min_highest_perf)
115 min_highest_perf = priority;
116
117 if (max_highest_perf > min_highest_perf)
118 schedule_work(&sched_itmt_work);
119 }
120
121 return 0;
122}
123
124#define ICPU(model) { X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, }
125
126static const struct x86_cpu_id itmt_legacy_cpu_ids[] = {
127 ICPU(INTEL_FAM6_BROADWELL_X),
128 ICPU(INTEL_FAM6_SKYLAKE_X),
129 {}
130};
131
132static int __init itmt_legacy_init(void)
133{
134 const struct x86_cpu_id *id;
135 int ret;
136
137 id = x86_match_cpu(itmt_legacy_cpu_ids);
138 if (!id)
139 return -ENODEV;
140
141 if (boot_cpu_has(X86_FEATURE_HWP))
142 return -ENODEV;
143
144 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
145 "platform/x86/turbo_max_3:online",
146 itmt_legacy_cpu_online, NULL);
147 if (ret < 0)
148 return ret;
149
150 return 0;
151}
152late_initcall(itmt_legacy_init)