Date:   Wed, 18 Jan 2017 21:15:32 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     "dvhart@...radead.org" <dvhart@...radead.org>,
        Andriy Shevchenko <andriy.shevchenko@...el.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] platform: x86: Support Turbo Boost Max 3.0 for non HWP systems

On Wed, Jan 18, 2017 at 8:29 PM, Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
> On platforms supporting Intel Turbo Boost Max Technology 3.0, the
> maximum turbo frequencies (turbo ratio) of some cores in a CPU package
> may be higher than the other cores in the same package.  In that case,
> better performance can be achieved by making the scheduler prefer to run
> tasks on the CPUs with higher max turbo frequencies.
>
> On Intel® Broadwell Xeon systems, it is optional to turn on HWP
> (Hardware P-States). When HWP is not turned on, the BIOS doesn't
> present required CPPC (Collaborative Processor Performance Control)
> tables. This table is used to get the per CPU core maximum performance
> ratio and inform scheduler (in cpufreq/intel_pstate driver).
>
> On such systems the maximum performance ratio can be read via over
> clocking (OC) mailbox interface for each CPU. This interface is not
> architectural and can change for every model of processors.
>
> This driver reads maximum performance ratio of each CPU and set up
> the scheduler priority metrics. In this way scheduler can prefer CPU
> with higher performance to schedule tasks.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

Replaces old version in testing, thanks.

P.S. My maintainer address in in @linux.intel.com.

> ---
> Change log:
> v2:
> - No functional change
> - Config renamed from INTEL_TURBO_BOOST_MAX_ENUMERATION to INTEL_TURBO_MAX_3
> - file renamed from intel_turbo_boost_max_enum.c to intel_turbo_max_3.c
> - Add "All rights reserved." in copyright header
> - Shorten lines by combining variable definition to single lines
>
>  drivers/platform/x86/Kconfig             |  10 ++
>  drivers/platform/x86/Makefile            |   1 +
>  drivers/platform/x86/intel_turbo_max_3.c | 152 +++++++++++++++++++++++++++++++
>  3 files changed, 163 insertions(+)
>  create mode 100644 drivers/platform/x86/intel_turbo_max_3.c
>
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 59aa8e3..081f07a 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1076,4 +1076,14 @@ config MLX_CPLD_PLATFORM
>           This driver handles hot-plug events for the power suppliers, power
>           cables and fans on the wide range Mellanox IB and Ethernet systems.
>
> +config INTEL_TURBO_MAX_3
> +       bool "Intel Turbo Boost Max Technology 3.0 enumeration driver"
> +       depends on X86_64 && SCHED_MC_PRIO
> +       ---help---
> +         This driver reads maximum performance ratio of each CPU and set up
> +         the scheduler priority metrics. In this way scheduler can prefer
> +         CPU with higher performance to schedule tasks.
> +         This driver is only required when the system is not using Hardware
> +         P-States (HWP). In HWP mode, priority can be read from ACPI tables.
> +
>  endif # X86_PLATFORM_DEVICES
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index d4111f0..cde7b4f 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -76,3 +76,4 @@ obj-$(CONFIG_INTEL_TELEMETRY) += intel_telemetry_core.o \
>  obj-$(CONFIG_INTEL_PMC_CORE)    += intel_pmc_core.o
>  obj-$(CONFIG_MLX_PLATFORM)     += mlx-platform.o
>  obj-$(CONFIG_MLX_CPLD_PLATFORM)        += mlxcpld-hotplug.o
> +obj-$(CONFIG_INTEL_TURBO_MAX_3) += intel_turbo_max_3.o
> diff --git a/drivers/platform/x86/intel_turbo_max_3.c b/drivers/platform/x86/intel_turbo_max_3.c
> new file mode 100644
> index 0000000..0103f5b
> --- /dev/null
> +++ b/drivers/platform/x86/intel_turbo_max_3.c
> @@ -0,0 +1,152 @@
> +/*
> + * 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@...ux.intel.com>");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4
>



-- 
With Best Regards,
Andy Shevchenko

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