linux-kernel - Re: [PATCH v2 3/7] thermal: intel: hfi: Minimally initialize the Hardware Feedback Interface

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Date:   Thu, 30 Dec 2021 19:43:22 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Amit Kucheria <amitk@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Lukasz Luba <lukasz.luba@....com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/7] thermal: intel: hfi: Minimally initialize the
 Hardware Feedback Interface

On Mon, Dec 20, 2021 at 4:23 PM Ricardo Neri
<ricardo.neri-calderon@...ux.intel.com> wrote:
>
> The Intel Hardware Feedback Interface provides guidance to the operating
> system about the performance and energy efficiency capabilities of each
> CPU in the system. Capabilities are numbers between 0 and 255 where a
> higher number represents a higher capability. For each CPU, energy
> efficiency and performance are reported as separate capabilities.
>
> Hardware computes these capabilities based on the operating conditions of
> the system such as power and thermal limits. These capabilities are shared
> with the operating system in a table resident in memory. Each package in
> the system has its own HFI instance. Every logical CPU in the package is
> represented in the table. More than one logical CPUs may be represented in
> a single table entry. When the hardware updates the table, it generates a
> package-level thermal interrupt.
>
> The size and format of the HFI table depend on the supported features and
> can only be determined at runtime. To minimally initialize the HFI, parse
> its features and allocate one instance per package of a data structure with
> the necessary parameters to read and navigate a local copy (i.e., owned by
> the driver) of individual HFI tables.
>
> A subsequent changeset will provide per-CPU initialization and interrupt
> handling.
>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Aubrey Li <aubrey.li@...ux.intel.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
> Reviewed-by: Len Brown <len.brown@...el.com>
> Co-developed by: Aubrey Li <aubrey.li@...ux.intel.com>
> Signed-off-by: Aubrey Li <aubrey.li@...ux.intel.com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---
> Changes since v1:
>   * Renamed X86_FEATURE_INTEL_HFI as X86_FEATURE_HFI. (Boris)
>   * Reworked parsing of HFI features using bitfields instead of bitmasks.
>     (PeterZ).
>   * Removed hfi_instance::parsed as hfi_parse_features() is called only
>     once via intel_hfi_init() via thermal_throttle_init_device().
>     (Rafael)
>   * Converted pr_err() to pr_debug(). (Srinivas, Rafael)
>   * Removed unnecessary dependency on CONFIG_SCHED_MC.
>   * Renamed hfi_instance::ts_counter as hfi_instance::timestamp.
>   * Renamed hfi_instance::table_base as hfi_instance::local_table and
>     relocated its definition to this patch.
>   * Wrapped hfi_instance::timestamp and hfi_instance:local_table in an
>     anonymous union, since both point at the same location.
> ---
>  drivers/thermal/intel/Kconfig       |  12 ++
>  drivers/thermal/intel/Makefile      |   1 +
>  drivers/thermal/intel/intel_hfi.c   | 175 ++++++++++++++++++++++++++++
>  drivers/thermal/intel/intel_hfi.h   |  11 ++
>  drivers/thermal/intel/therm_throt.c |   3 +
>  5 files changed, 202 insertions(+)
>  create mode 100644 drivers/thermal/intel/intel_hfi.c
>  create mode 100644 drivers/thermal/intel/intel_hfi.h
>
> diff --git a/drivers/thermal/intel/Kconfig b/drivers/thermal/intel/Kconfig
> index c83ea5d04a1d..1a21ff60fdc7 100644
> --- a/drivers/thermal/intel/Kconfig
> +++ b/drivers/thermal/intel/Kconfig
> @@ -99,3 +99,15 @@ config INTEL_MENLOW
>           Intel Menlow platform.
>
>           If unsure, say N.
> +
> +config INTEL_HFI

This looks like it may be too general, because HFI is not a thermal-only thing.

Maybe cal it INTEL_HFI_THERMAL?