LXR linux/drivers/platform/x86/intel_turbo_max

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Intel Turbo Boost Max Technology 3.0 legacy (non HWP) enumeration driver
   4 * Copyright (c) 2017, Intel Corporation.
   5 * All rights reserved.
   6 *
   7 * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
   8 */
   9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11#include <linux/cpufeature.h>
  12#include <linux/cpuhotplug.h>
  13#include <linux/init.h>
  14#include <linux/kernel.h>
  15#include <linux/topology.h>
  16#include <linux/workqueue.h>
  17
  18#include <asm/cpu_device_id.h>
  19#include <asm/intel-family.h>
  20
  21#define MSR_OC_MAILBOX                  0x150
  22#define MSR_OC_MAILBOX_CMD_OFFSET       32
  23#define MSR_OC_MAILBOX_RSP_OFFSET       32
  24#define MSR_OC_MAILBOX_BUSY_BIT         63
  25#define OC_MAILBOX_FC_CONTROL_CMD       0x1C
  26
  27/*
  28 * Typical latency to get mail box response is ~3us, It takes +3 us to
  29 * process reading mailbox after issuing mailbox write on a Broadwell 3.4 GHz
  30 * system. So for most of the time, the first mailbox read should have the
  31 * response, but to avoid some boundary cases retry twice.
  32 */
  33#define OC_MAILBOX_RETRY_COUNT          2
  34
  35static int get_oc_core_priority(unsigned int cpu)
  36{
  37        u64 value, cmd = OC_MAILBOX_FC_CONTROL_CMD;
  38        int ret, i;
  39
  40        /* Issue favored core read command */
  41        value = cmd << MSR_OC_MAILBOX_CMD_OFFSET;
  42        /* Set the busy bit to indicate OS is trying to issue command */
  43        value |=  BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT);
  44        ret = wrmsrl_safe(MSR_OC_MAILBOX, value);
  45        if (ret) {
  46                pr_debug("cpu %d OC mailbox write failed\n", cpu);
  47                return ret;
  48        }
  49
  50        for (i = 0; i < OC_MAILBOX_RETRY_COUNT; ++i) {
  51                ret = rdmsrl_safe(MSR_OC_MAILBOX, &value);
  52                if (ret) {
  53                        pr_debug("cpu %d OC mailbox read failed\n", cpu);
  54                        break;
  55                }
  56
  57                if (value & BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT)) {
  58                        pr_debug("cpu %d OC mailbox still processing\n", cpu);
  59                        ret = -EBUSY;
  60                        continue;
  61                }
  62
  63                if ((value >> MSR_OC_MAILBOX_RSP_OFFSET) & 0xff) {
  64                        pr_debug("cpu %d OC mailbox cmd failed\n", cpu);
  65                        ret = -ENXIO;
  66                        break;
  67                }
  68
  69                ret = value & 0xff;
  70                pr_debug("cpu %d max_ratio %d\n", cpu, ret);
  71                break;
  72        }
  73
  74        return ret;
  75}
  76
  77/*
  78 * The work item is needed to avoid CPU hotplug locking issues. The function
  79 * itmt_legacy_set_priority() is called from CPU online callback, so can't
  80 * call sched_set_itmt_support() from there as this function will aquire
  81 * hotplug locks in its path.
  82 */
  83static void itmt_legacy_work_fn(struct work_struct *work)
  84{
  85        sched_set_itmt_support();
  86}
  87
  88static DECLARE_WORK(sched_itmt_work, itmt_legacy_work_fn);
  89
  90static int itmt_legacy_cpu_online(unsigned int cpu)
  91{
  92        static u32 max_highest_perf = 0, min_highest_perf = U32_MAX;
  93        int priority;
  94
  95        priority = get_oc_core_priority(cpu);
  96        if (priority < 0)
  97                return 0;
  98
  99        sched_set_itmt_core_prio(priority, cpu);
 100
 101        /* Enable ITMT feature when a core with different priority is found */
 102        if (max_highest_perf <= min_highest_perf) {
 103                if (priority > max_highest_perf)
 104                        max_highest_perf = priority;
 105
 106                if (priority < min_highest_perf)
 107                        min_highest_perf = priority;
 108
 109                if (max_highest_perf > min_highest_perf)
 110                        schedule_work(&sched_itmt_work);
 111        }
 112
 113        return 0;
 114}
 115
 116static const struct x86_cpu_id itmt_legacy_cpu_ids[] = {
 117        X86_MATCH_INTEL_FAM6_MODEL(BROADWELL_X, NULL),
 118        X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE_X,   NULL),
 119        {}
 120};
 121
 122static int __init itmt_legacy_init(void)
 123{
 124        const struct x86_cpu_id *id;
 125        int ret;
 126
 127        id = x86_match_cpu(itmt_legacy_cpu_ids);
 128        if (!id)
 129                return -ENODEV;
 130
 131        ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 132                                "platform/x86/turbo_max_3:online",
 133                                itmt_legacy_cpu_online, NULL);
 134        if (ret < 0)
 135                return ret;
 136
 137        return 0;
 138}
 139late_initcall(itmt_legacy_init)
 140