Re: [PATCH v3 3/5] acpi: Introduce new function callback for _OSC

[Rafael J. Wysocki]

On Fri, Jun 30, 2023 at 11:02 AM Wilczynski, Michal
<michal.wilczynski@xxxxxxxxx> wrote:
>
>
>
> On 6/29/2023 3:15 PM, Rafael J. Wysocki wrote:
> > On Thu, Jun 29, 2023 at 1:04 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> >> I would just say "Introduce acpi_processor_osc()" in the subject and
> >> then explain its role in the changelog.
> >>
> >> On Tue, Jun 13, 2023 at 6:12 PM Michal Wilczynski
> >> <michal.wilczynski@xxxxxxxxx> wrote:
> >>> Currently in ACPI code _OSC method is already used for workaround
> >>> introduced in commit a21211672c9a ("ACPI / processor: Request native
> >>> thermal interrupt handling via _OSC"). Create new function, similar to
> >>> already existing acpi_hwp_native_thermal_lvt_osc(). Call new function
> >>> acpi_processor_osc(). Make this function fulfill the purpose previously
> >>> fulfilled by the workaround plus convey OSPM processor capabilities
> >>> with it by setting correct processor capability bits.
> >>>
> >>> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >>> Signed-off-by: Michal Wilczynski <michal.wilczynski@xxxxxxxxx>
> >>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> >>> ---
> >>>  arch/x86/include/asm/acpi.h   |  3 +++
> >>>  drivers/acpi/acpi_processor.c | 43 ++++++++++++++++++++++++++++++++++-
> >>>  include/acpi/pdc_intel.h      |  1 +
> >>>  3 files changed, 46 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
> >>> index 6a498d1781e7..6c25ce2dad18 100644
> >>> --- a/arch/x86/include/asm/acpi.h
> >>> +++ b/arch/x86/include/asm/acpi.h
> >>> @@ -112,6 +112,9 @@ static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
> >>>         if (cpu_has(c, X86_FEATURE_ACPI))
> >>>                 *cap |= ACPI_PDC_T_FFH;
> >>>
> >>> +       if (cpu_has(c, X86_FEATURE_HWP))
> >>> +               *cap |= ACPI_PDC_COLLAB_PROC_PERF;
> >>> +
> >>>         /*
> >>>          * If mwait/monitor is unsupported, C2/C3_FFH will be disabled
> >>>          */
> >>> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> >>> index 8c5d0295a042..0de0b05b6f53 100644
> >>> --- a/drivers/acpi/acpi_processor.c
> >>> +++ b/drivers/acpi/acpi_processor.c
> >>> @@ -591,13 +591,54 @@ void __init processor_dmi_check(void)
> >>>         dmi_check_system(processor_idle_dmi_table);
> >>>  }
> >>>
> >>> +/* vendor specific UUID indicating an Intel platform */
> >>> +static u8 sb_uuid_str[] = "4077A616-290C-47BE-9EBD-D87058713953";
> >>>  static bool acpi_hwp_native_thermal_lvt_set;
> >>> +static acpi_status __init acpi_processor_osc(acpi_handle handle, u32 lvl,
> >>> +                                            void *context, void **rv)
> >>> +{
> >>> +       u32 capbuf[2] = {};
> >>> +       acpi_status status;
> >>> +       struct acpi_osc_context osc_context = {
> >>> +               .uuid_str = sb_uuid_str,
> >>> +               .rev = 1,
> >>> +               .cap.length = 8,
> >>> +               .cap.pointer = capbuf,
> >>> +       };
> >>> +
> >>> +       if (processor_physically_present(handle) == false)
> >> if (!processor_physically_present(handle))
> >>
> >>> +               return AE_OK;
> >>> +
> >>> +       arch_acpi_set_proc_cap_bits(&capbuf[OSC_SUPPORT_DWORD]);
> >>> +
> >>> +       if (boot_option_idle_override == IDLE_NOMWAIT)
> >>> +               capbuf[OSC_SUPPORT_DWORD] &=
> >>> +                       ~(ACPI_PDC_C_C2C3_FFH | ACPI_PDC_C_C1_FFH);
> >>> +
> >>> +       status = acpi_run_osc(handle, &osc_context);
> >>> +       if (ACPI_FAILURE(status))
> >>> +               return status;
> >>> +
> >>> +       if (osc_context.ret.pointer && osc_context.ret.length > 1) {
> >>> +               u32 *capbuf_ret = osc_context.ret.pointer;
> >>> +
> >>> +               if (!acpi_hwp_native_thermal_lvt_set &&
> >>> +                   capbuf_ret[1] & ACPI_PDC_COLLAB_PROC_PERF) {
> >> Checking it in capbuf_ret[] if it was not set in capbuf[] is sort of
> >> questionable.
> >>
> >> Note that acpi_hwp_native_thermal_lvt_osc() sets it in capbuf[] before
> >> calling acpi_run_osc().
> > So you moved setting it to arch_acpi_set_proc_cap_bits(), but then it
> > should also be checked by the arch code.  That is, add an arch
> > function to check if a given bit is set in the returned capabilities
> > buffer (passed as an argument).
>
> Hmm, maybe that's true, but the only reason we check that is so we can print
> a debug message

No, it is not the only reason.  The more important part is to set
acpi_hwp_native_thermal_lvt_set if it is still unset at that point.

>  - that's pretty much a leftover after a workaround. Introducing
> more arch code to accommodate this seemed wasteful, since in my understanding
> all workarounds are meant to be removed at some point, even if it takes a long time
> to do so.

Not really, until the systems needing them are in use.

> >
> > Also it can be argued that ACPI_PDC_C_C2C3_FFH and ACPI_PDC_C_C1_FFH
> > should be set by the arch code too.
>
> That makes sense, but technically is also a workaround, since we're basically
> checking for some specific DMI's and then we disable mwait for them.

But boot_option_idle_override is set by the arch code, isn't it?

So the arch code may as well do the quirk in accordance with it.