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/*
* Intel Turbo Boost Max Technology 3.0 legacy (non HWP) enumeration driver
* Copyright (c) 2017, Intel Corporation.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/cpuhotplug.h>
#include <linux/cpufeature.h>
#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#define MSR_OC_MAILBOX 0x150
#define MSR_OC_MAILBOX_CMD_OFFSET 32
#define MSR_OC_MAILBOX_RSP_OFFSET 32
#define MSR_OC_MAILBOX_BUSY_BIT 63
#define OC_MAILBOX_FC_CONTROL_CMD 0x1C
/*
* Typical latency to get mail box response is ~3us, It takes +3 us to
* process reading mailbox after issuing mailbox write on a Broadwell 3.4 GHz
* system. So for most of the time, the first mailbox read should have the
* response, but to avoid some boundary cases retry twice.
*/
#define OC_MAILBOX_RETRY_COUNT 2
static int get_oc_core_priority(unsigned int cpu)
{
u64 value, cmd = OC_MAILBOX_FC_CONTROL_CMD;
int ret, i;
/* Issue favored core read command */
value = cmd << MSR_OC_MAILBOX_CMD_OFFSET;
/* Set the busy bit to indicate OS is trying to issue command */
value |= BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT);
ret = wrmsrl_safe(MSR_OC_MAILBOX, value);
if (ret) {
pr_debug("cpu %d OC mailbox write failed\n", cpu);
return ret;
}
for (i = 0; i < OC_MAILBOX_RETRY_COUNT; ++i) {
ret = rdmsrl_safe(MSR_OC_MAILBOX, &value);
if (ret) {
pr_debug("cpu %d OC mailbox read failed\n", cpu);
break;
}
if (value & BIT_ULL(MSR_OC_MAILBOX_BUSY_BIT)) {
pr_debug("cpu %d OC mailbox still processing\n", cpu);
ret = -EBUSY;
continue;
}
if ((value >> MSR_OC_MAILBOX_RSP_OFFSET) & 0xff) {
pr_debug("cpu %d OC mailbox cmd failed\n", cpu);
ret = -ENXIO;
break;
}
ret = value & 0xff;
pr_debug("cpu %d max_ratio %d\n", cpu, ret);
break;
}
return ret;
}
/*
* The work item is needed to avoid CPU hotplug locking issues. The function
* itmt_legacy_set_priority() is called from CPU online callback, so can't
* call sched_set_itmt_support() from there as this function will aquire
* hotplug locks in its path.
*/
static void itmt_legacy_work_fn(struct work_struct *work)
{
sched_set_itmt_support();
}
static DECLARE_WORK(sched_itmt_work, itmt_legacy_work_fn);
static int itmt_legacy_cpu_online(unsigned int cpu)
{
static u32 max_highest_perf = 0, min_highest_perf = U32_MAX;
int priority;
priority = get_oc_core_priority(cpu);
if (priority < 0)
return 0;
sched_set_itmt_core_prio(priority, cpu);
/* Enable ITMT feature when a core with different priority is found */
if (max_highest_perf <= min_highest_perf) {
if (priority > max_highest_perf)
max_highest_perf = priority;
if (priority < min_highest_perf)
min_highest_perf = priority;
if (max_highest_perf > min_highest_perf)
schedule_work(&sched_itmt_work);
}
return 0;
}
#define ICPU(model) { X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, }
static const struct x86_cpu_id itmt_legacy_cpu_ids[] = {
ICPU(INTEL_FAM6_BROADWELL_X),
{}
};
MODULE_DEVICE_TABLE(x86cpu, itmt_legacy_cpu_ids);
static int __init itmt_legacy_init(void)
{
const struct x86_cpu_id *id;
int ret;
id = x86_match_cpu(itmt_legacy_cpu_ids);
if (!id)
return -ENODEV;
if (boot_cpu_has(X86_FEATURE_HWP))
return -ENODEV;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
"platform/x86/turbo_max_3:online",
itmt_legacy_cpu_online, NULL);
if (ret < 0)
return ret;
return 0;
}
late_initcall(itmt_legacy_init)
MODULE_DESCRIPTION("Intel Turbo Boost Max 3.0 enumeration driver");
MODULE_AUTHOR("Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>");
MODULE_LICENSE("GPL v2");
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