On Tue, 2015-07-21 at 19:37 +0300, Konstantin Khlebnikov wrote: > On 21.07.2015 18:37, Srinivas Pandruvada wrote: > > On Tue, 2015-07-21 at 13:25 +0300, Konstantin Khlebnikov wrote: > >> On 21.07.2015 00:08, Srinivas Pandruvada wrote: > >>> On Fri, 2015-07-17 at 07:36 +0300, Konstantin Khlebnikov wrote: > >>>> On Fri, Jul 17, 2015 at 1:08 AM, Srinivas Pandruvada > >>>> <srinivas.pandruv...@linux.intel.com> wrote: > >>>>> On Thu, 2015-07-16 at 21:17 +0300, Konstantin Khlebnikov wrote: > >>>>>> IPMI can control CPU P-states remotely: configuration is reported via > >>>>>> common ACPI interface (_PPC/_PSS/etc). This patch adds required minimal > >>>>>> support in intel_pstate to receive and use these P-state limits. > >>>>>> > >>>>>> * ignore limit of top state in _PPC: it lower than turbo boost > >>>>>> frequency > >>>>>> * register intel_pstate in acpi-processor to get states from _PSS > >>>>>> * link acpi_processor_get_bios_limit: this adds attribute "bios_limit" > >>>>>> > >>>>>> Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru> > >>>>>> --- > >>>>>> drivers/acpi/processor_perflib.c | 3 +- > >>>>>> drivers/cpufreq/intel_pstate.c | 57 > >>>>>> ++++++++++++++++++++++++++++++++++++++ > >>>>>> 2 files changed, 59 insertions(+), 1 deletion(-) > >>>>>> > >>>>>> diff --git a/drivers/acpi/processor_perflib.c > >>>>>> b/drivers/acpi/processor_perflib.c > >>>>>> index cfc8aba72f86..781e328c9d5f 100644 > >>>>>> --- a/drivers/acpi/processor_perflib.c > >>>>>> +++ b/drivers/acpi/processor_perflib.c > >>>>>> @@ -98,7 +98,8 @@ static int acpi_processor_ppc_notifier(struct > >>>>>> notifier_block *nb, > >>>>>> > >>>>>> ppc = (unsigned int)pr->performance_platform_limit; > >>>>>> > >>>>>> - if (ppc >= pr->performance->state_count) > >>>>>> + /* Ignore limit of top state: it lower than turbo boost > >>>>>> frequency */ > >>>>>> + if (!ppc || ppc >= pr->performance->state_count) > >>>>> Why? Isn't the previous check enough? > >>>> > >>>> Zero _PPC state must be top performance state but as I see frequency in > >>>> _PSS is lower than maximum possible turbo frequency. So, in this case > >>>> intel_pstate cannnot get "100%" for max bound even it there is no limit > >>>> set. > >>>> > >>>> For example: I saw _PSS[0] = 2601 Mhz, PSS[1] = 2600 Mhz while turbo > >>>> state is 3400 Mhz. > >>>> > >>> Have you tested dynamic _PPC modification with acpi cpufreq with this > >>> change (after boot)? Suppose _PPC is changed from 3 to 0, then > >>> cpufreq_verify_within_limits will not be called to change to new max > >>> turbo performance state. > >>> > >> > >> I haven't checked that but as I see acpi_processor_ppc_notifier() > >> can only reduce maximum frequency. So, there should be no problem > >> in this case. > > No, it can also be used in both ways. Once reduced, it can increase as > > well. _PPC can be dynamically modified by BIOS to reduce and also to > > increase. > > Well, in this case BIOS will trigger ACPI_PROCESSOR_NOTIFY_PERFORMANCE: > kernel evaluate new _PPC and call cpufreq_update_policy() > which set initial frequency min/max range according to user setup and > apply all limits after that. Initial policy->user_policy.min/max stay > unchanged. So, that dynamic modification works in both ways. > Fair enough. We need to take account for _PSS. We have some changes for this, but not gone through test cycle. I will post them as RFC, please check. Thanks for your patience.
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