linux-kernel - Re: [PATCH v4 0/9] Prefer using _OSC method over deprecated

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Date:   Fri, 14 Jul 2023 18:12:50 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Michal Wilczynski <michal.wilczynski@...el.com>
Cc:     linux-acpi@...r.kernel.org, rafael@...nel.org,
        andriy.shevchenko@...el.com, artem.bityutskiy@...ux.intel.com,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, lenb@...nel.org, jgross@...e.com,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 0/9] Prefer using _OSC method over deprecated _PDC

On Mon, Jul 10, 2023 at 4:06 PM Michal Wilczynski
<michal.wilczynski@...el.com> wrote:
>
> ACPI 3.0 introduced a new Operating System Capabilities _OSC control
> method. This method is similar to _PDC, which was marked as deprecated
> in ACPI 3.0.
>
> Prefer using _OSC method over deprecated _PDC in the acpi_bus_init(). In
> case of the failure of the _OSC, try using _PDC as a fallback.
>
> Testing done:
> Tested on physical server with BIOS implementing _OSC methods. In this
> case acpi_processor_osc() was executed for each CPU core. acpi_run_osc()
> returned success indicating that _OSC method succeeded.
>
> Tested on qemu VM to check whether the code would work on a SeaBios (the
> default for qemu, doesn't support _OSC methods, or _PDC). This way I was
> able to see how code behaves in case BIOS doesn't implement _OSC. In
> that case the function
> acpi_run_osc() returned failure, which propagated all the way up to
> acpi_early_processor_osc(). The logic responsible for triggering _PDC
> execution was triggered correctly.
>
> Tested this using debug messages with printk.
>
> v4:
>  - move setting processor capabilities bits into arch code
>  - move workaround for mwait to acpi/x86 directory
>  - rename ACPI_PDC* constants to more generic ACPI_PROC_CAP*
>  - introduce new function acpi_early_processor_control_setup()
>
> v3:
>  - split into more commits to make review easier
>  - changed "_UID" to METHOD_NAME_UID
>  - changed hard-coded constant to ACPI_PDC_COLLAB_PROC_PERF
>  - added Suggested-by tags
>  - fixed style issues
>  - fixed whitespaces
>  - refactored code
> v2:
>  - fixed compilation issues on ia64 and arm
>
> Michal Wilczynski (9):
>   acpi: Move mwait quirk out of acpi_processor.c
>   acpi: Move processor_physically_present() to acpi_processor.c
>   acpi: Refactor arch_acpi_set_pdc_bits()
>   acpi: Rename ACPI_PDC constants
>   acpi: Clear C_C2C3_FFH and C_C1_FFH in arch_acpi_set_proc_cap_bits()
>   acpi: Move setting CAP_SMP_T_SWCOORD to arch_acpi_set_proc_cap_bits()
>   acpi: Introduce acpi_processor_osc()
>   acpi: Use _OSC method to convey processor OSPM capabilities
>   acpi: Remove acpi_hwp_native_thermal_lvt_osc()

I have made a number of changes to the patches (edited subjects,
rewrote changelogs, fixed up whitespace in a few places, changed the
return value of acpi_early_processor_osc() to bool and made it static
etc.) and tentatively queued them up for 6.6.  Please see the
bleeding-edge branch of linux-pm.git.

I have made sure that the series will still compile at least on
x86-64, but testing it again would be appreciated.

Thanks!