Messages in this thread |  | | From | "Rafael J. Wysocki" <> | | Date | Tue, 14 Jan 2025 15:37:47 +0100 | | Subject | Re: [PATCH 2/6] cpuidle: Introduce CPUIDLE_FLAG_MWAIT |
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On Tue, Jan 14, 2025 at 3:34 PM Sudeep Holla <sudeep.holla@arm.com> wrote: > > On Tue, Jan 14, 2025 at 03:01:26PM +0100, Rafael J. Wysocki wrote: > > On Thu, Jan 2, 2025 at 4:02 PM Frederic Weisbecker <frederic@kernel.org> wrote: > > > > > > From: Peter Zijlstra <peterz@infradead.org> > > > > > > Provide a way to tell the cpuidle core about states monitoring > > > TIF_NEED_RESCHED on the hardware level, monitor/mwait users being the > > > only examples in use. > > > > > > This will allow cpuidle core to manage TIF_NR_POLLING on behalf of all > > > kinds of TIF_NEED_RESCHED watching states while keeping a necessary > > > distinction for the governors between software loops polling on > > > TIF_NEED_RESCHED and hardware monitored writes to thread flags. > > > > > > [fweisbec: _ Initialize flag from acpi_processor_setup_cstates() instead > > > of acpi_processor_setup_lpi_states(), as the latter seem to > > > be about arm64... > > > _ Rename CPUIDLE_FLAG_NO_IPI to CPUIDLE_FLAG_MWAIT] > > > > > > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > > > Signed-off-by: Frederic Weisbecker <frederic@kernel.org> > > > --- > > > drivers/acpi/processor_idle.c | 3 +++ > > > drivers/idle/intel_idle.c | 5 ++++- > > > include/linux/cpuidle.h | 1 + > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c > > > index 698897b29de2..66cb5536d91e 100644 > > > --- a/drivers/acpi/processor_idle.c > > > +++ b/drivers/acpi/processor_idle.c > > > @@ -806,6 +806,9 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr) > > > if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2) > > > drv->safe_state_index = count; > > > > > > + if (cx->entry_method == ACPI_CSTATE_FFH) > > > + state->flags |= CPUIDLE_FLAG_MWAIT; > > > > FFH need not mean MWAIT in principle. > > > > FFH in _CST means MWAIT in practice because _CST is used on x86 which > > implements FFH through MWAIT, but it would be good at least to put a > > comment here to explain that this code is only expected to run on x86. > > > > Or better still, add something like acpi_arch_idle_state_flags(u8 > > entry_method) that will return CPUIDLE_FLAG_MWAIT for ACPI_CSTATE_FFH > > and 0 otherwise and then do > > > > state->flags |= acpi_arch_idle_state_flags(cx->entry_method); > > > > +1, was about to suggest the same. Though I am not aware of any Arm platforms > using C-States(LPI was added to suit Arm requirements), it is better to keep > the FFH definition arch specific.
Which will be consistent with this patch among other things:
https://lore.kernel.org/linux-pm/20250110115953.6058-3-patryk.wlazlyn@linux.intel.com/
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