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Date:   Wed, 13 Jul 2022 16:53:49 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Dapeng Mi <dapeng1.mi@intel.com>, Arnd Bergmann <arnd@arndb.de>,
        Bart Van Assche <bvanassche@acm.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [PATCH] cpuidle: Move cpuidle driver forward before acpi driver
 in Makefile
Message-ID: <20220713165237-mutt-send-email-mst@kernel.org>
References: <20220713082426.850911-1-dapeng1.mi@intel.com>
 <CAJZ5v0gsHPav5Ax6+9OMmeApqn7qdJPQmo5MMh=ba6Rtj5NnQA@mail.gmail.com>
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On Wed, Jul 13, 2022 at 07:53:13PM +0200, Rafael J. Wysocki wrote:
> On Wed, Jul 13, 2022 at 10:21 AM Dapeng Mi <dapeng1.mi@intel.com> wrote:
> >
> > As long as Kconfig ACPI_PROCESSOR is enabled, ACPI_PROCESSOR would
> > select ACPI_PROCESSOR_IDLE and acpi_idle driver is enabled. But
> > in current driver loading order acpi_idle driver is always loaded
> > before cpuidle_haltpoll driver. This leads to cpuidle_hatpoll driver
> > has no chance to be loaded when it's enabled.
> >
> > Thus, move cpuidle driver forward before acpi driver and make
> > cpuidle-hatpoll driver has a chance to be run when it's enabled.
> >
> > Signed-off-by: Dapeng Mi <dapeng1.mi@intel.com>
> > ---
> >  drivers/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/Makefile b/drivers/Makefile
> > index 9a30842b22c5..921ed481b520 100644
> > --- a/drivers/Makefile
> > +++ b/drivers/Makefile
> > @@ -26,6 +26,7 @@ obj-y                         += idle/
> >  # IPMI must come before ACPI in order to provide IPMI opregion support
> >  obj-y                          += char/ipmi/
> >
> > +obj-$(CONFIG_CPU_IDLE)         += cpuidle/
> >  obj-$(CONFIG_ACPI)             += acpi/
> >
> >  # PnP must come after ACPI since it will eventually need to check if acpi
> > @@ -126,7 +127,6 @@ obj-$(CONFIG_EDAC)          += edac/
> >  obj-$(CONFIG_EISA)             += eisa/
> >  obj-$(CONFIG_PM_OPP)           += opp/
> >  obj-$(CONFIG_CPU_FREQ)         += cpufreq/
> > -obj-$(CONFIG_CPU_IDLE)         += cpuidle/
> >  obj-y                          += mmc/
> >  obj-y                          += ufs/
> >  obj-$(CONFIG_MEMSTICK)         += memstick/
> > --
> 
> Well, this change doesn't guarantee loading haltpoll before ACPI idle.
> 
> Also what if haltpoll is enabled, but the user wants ACPI idle?

Exactly. For example while on real boxes BIOS might often present broken
ACPI idle, on VMs I am guessing if ACPI is present one can assume it's
actually correct.

-- 
MST