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.pandruvada@xxxxxxxxxxxxxxx> 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 <khlebnikov@xxxxxxxxxxxxxx>
---
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.
--
Konstantin
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