[PATCH V2] SKL intel_pstate update MSR values when changing governors

[PATCH V2] SKL intel_pstate update MSR values when changing governors

[Alexandra Yates]

From: root <root@skl-s-fedora22.jf.intel.com>

When changing from powersave to performance governors
Intel_pstate fails to update the MSR values that reflect the
max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:

Governor 	MSR			max_perf_pct
=========	========		============
Powersave 	80002808		100%
Powersave	80002008		80%
Performance	80002028 [error]	100%
Performance	80002828 [expected]	100%

The line label [error] shows the culprit. At this point the MSR
should reflect the max_perf_pct that is 100%, that corresponds
to MSR 80002828 as shown on the next line of the example. Which
is the maximum performance for the Performance governor.
Instead it holds back the MSR value previously set by the
Powersave, in this case 80002028.

This patch allows the system to print the correct MSR value
80002828 that corresponds to the 100% max_perf_pct when changing
from powersave to performance governors.

For more information on the MSR values for SKL please visit
ISDM under Managing HWP.

Signed-off-by: root <root@skl-s-fedora22.jf.intel.com>
---
 drivers/cpufreq/intel_pstate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 2e31d09..0eeb7da 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 	    policy->max >= policy->cpuinfo.max_freq) {
 		pr_debug("intel_pstate: set performance\n");
 		limits = &performance_limits;
+		if (hwp_active)
+			intel_pstate_hwp_set();
 		return 0;
 	}
 
-- 
1.9.1

Re: [PATCH V2] SKL intel_pstate update MSR values when changing governors

[Srinivas Pandruvada]

On Tue, 2015-11-17 at 17:58 -0800, Alexandra Yates wrote:
> From: root <root@skl-s-fedora22.jf.intel.com>
You need to fix the git config ...
The change itself is OK.

Thanks,
Srinivas
> 
> When changing from powersave to performance governors
> Intel_pstate fails to update the MSR values that reflect the
> max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:
> 
> Governor 	MSR			max_perf_pct
> =========	========		============
> Powersave 	80002808		100%
> Powersave	80002008		80%
> Performance	80002028 [error]	100%
> Performance	80002828 [expected]	100%
> 
> The line label [error] shows the culprit. At this point the MSR
> should reflect the max_perf_pct that is 100%, that corresponds
> to MSR 80002828 as shown on the next line of the example. Which
> is the maximum performance for the Performance governor.
> Instead it holds back the MSR value previously set by the
> Powersave, in this case 80002028.
> 
> This patch allows the system to print the correct MSR value
> 80002828 that corresponds to the 100% max_perf_pct when changing
> from powersave to performance governors.
> 
> For more information on the MSR values for SKL please visit
> ISDM under Managing HWP.
> 
> Signed-off-by: root <root@skl-s-fedora22.jf.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 2e31d09..0eeb7da 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>  	    policy->max >= policy->cpuinfo.max_freq) {
>  		pr_debug("intel_pstate: set performance\n");
>  		limits = &performance_limits;
> +		if (hwp_active)
> +			intel_pstate_hwp_set();
>  		return 0;
>  	}
>  

[PATCH V3] SKL intel_pstate update MSR values when changing governors

[Alexandra Yates]

When changing from powersave to performance governors
Intel_pstate fails to update the MSR values that reflect the
max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:

Governor 	MSR			max_perf_pct
=========	========		============
Powersave 	80002808		100%
Powersave	80002008		80%
Performance	80002028 [error]	100%
Performance	80002828 [expected]	100%

The line label [error] shows the culprit. At this point the MSR
should reflect the max_perf_pct that is 100%, that corresponds
to MSR 80002828 as shown on the next line of the example. Which
is the maximum performance for the Performance governor.
Instead it holds back the MSR value previously set by the
Powersave, in this case 80002028.

This patch allows the system to print the correct MSR value
80002828 that corresponds to the 100% max_perf_pct when changing
from powersave to performance governors.

For more information on the MSR values for SKL please visit
ISDM under Managing HWP.

Signed-off-by: Alexandra Yates <alexandra.yates@linux.intel.com>
---
 drivers/cpufreq/intel_pstate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 2e31d09..0eeb7da 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 	    policy->max >= policy->cpuinfo.max_freq) {
 		pr_debug("intel_pstate: set performance\n");
 		limits = &performance_limits;
+		if (hwp_active)
+			intel_pstate_hwp_set();
 		return 0;
 	}
 
-- 
1.9.1

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Srinivas Pandruvada]

On 11/18/2015 02:58 PM, Alexandra Yates wrote:
> When changing from powersave to performance governors
> Intel_pstate fails to update the MSR values that reflect the
> max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:
>
> Governor 	MSR			max_perf_pct
> =========	========		============
> Powersave 	80002808		100%
> Powersave	80002008		80%
> Performance	80002028 [error]	100%
> Performance	80002828 [expected]	100%
>
> The line label [error] shows the culprit. At this point the MSR
> should reflect the max_perf_pct that is 100%, that corresponds
> to MSR 80002828 as shown on the next line of the example. Which
> is the maximum performance for the Performance governor.
> Instead it holds back the MSR value previously set by the
> Powersave, in this case 80002028.
>
> This patch allows the system to print the correct MSR value
> 80002828 that corresponds to the 100% max_perf_pct when changing
> from powersave to performance governors.
>
> For more information on the MSR values for SKL please visit
> ISDM under Managing HWP.
>
> Signed-off-by: Alexandra Yates <alexandra.yates@linux.intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
>   drivers/cpufreq/intel_pstate.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 2e31d09..0eeb7da 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>   	    policy->max >= policy->cpuinfo.max_freq) {
>   		pr_debug("intel_pstate: set performance\n");
>   		limits = &performance_limits;
> +		if (hwp_active)
> +			intel_pstate_hwp_set();
>   		return 0;
>   	}
>
>

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Rafael J. Wysocki]

Hi,

On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
>
> On 11/18/2015 02:58 PM, Alexandra Yates wrote:
>>
>> When changing from powersave to performance governors
>> Intel_pstate fails to update the MSR values that reflect the
>> max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:
>>
>> Governor        MSR                     max_perf_pct
>> =========       ========                ============
>> Powersave       80002808                100%
>> Powersave       80002008                80%
>> Performance     80002028 [error]        100%
>> Performance     80002828 [expected]     100%
>>
>> The line label [error] shows the culprit. At this point the MSR
>> should reflect the max_perf_pct that is 100%, that corresponds
>> to MSR 80002828 as shown on the next line of the example. Which
>> is the maximum performance for the Performance governor.
>> Instead it holds back the MSR value previously set by the
>> Powersave, in this case 80002028.
>>
>> This patch allows the system to print the correct MSR value
>> 80002828 that corresponds to the 100% max_perf_pct when changing
>> from powersave to performance governors.

Is this only about what is printed or does it mean that the driver
actually uses an incorrect MSR value?

>> For more information on the MSR values for SKL please visit
>> ISDM under Managing HWP.
>>
>> Signed-off-by: Alexandra Yates <alexandra.yates@linux.intel.com>
>
> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>>
>> ---
>>   drivers/cpufreq/intel_pstate.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/cpufreq/intel_pstate.c
>> b/drivers/cpufreq/intel_pstate.c
>> index 2e31d09..0eeb7da 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct
>> cpufreq_policy *policy)
>>             policy->max >= policy->cpuinfo.max_freq) {
>>                 pr_debug("intel_pstate: set performance\n");
>>                 limits = &performance_limits;
>> +               if (hwp_active)
>> +                       intel_pstate_hwp_set();

Honestly, I'm not really sure how this is matching the changelog.

What it does is to ensure that the correct limits are used when in the
HWP mode too as far as I can say.  Is my understanding correct here?

>>                 return 0;
>>         }
>>
>>
> --

Thanks,
Rafael

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Srinivas Pandruvada]

On Tue, 2015-11-24 at 02:09 +0100, Rafael J. Wysocki wrote:
> Hi,
> 
> On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> >
> >
> > On 11/18/2015 02:58 PM, Alexandra Yates wrote:
> >>
> >> When changing from powersave to performance governors
> >> Intel_pstate fails to update the MSR values that reflect the
> >> max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774:
> >>
> >> Governor        MSR                     max_perf_pct
> >> =========       ========                ============
> >> Powersave       80002808                100%
> >> Powersave       80002008                80%
> >> Performance     80002028 [error]        100%
> >> Performance     80002828 [expected]     100%
> >>
> >> The line label [error] shows the culprit. At this point the MSR
> >> should reflect the max_perf_pct that is 100%, that corresponds
> >> to MSR 80002828 as shown on the next line of the example. Which
> >> is the maximum performance for the Performance governor.
> >> Instead it holds back the MSR value previously set by the
> >> Powersave, in this case 80002028.
> >>
> >> This patch allows the system to print the correct MSR value
> >> 80002828 that corresponds to the 100% max_perf_pct when changing
> >> from powersave to performance governors.
> 
> Is this only about what is printed or does it mean that the driver
> actually uses an incorrect MSR value?
Driver was not configuring correct value in HWP MSR, which sets min and
max limits, so the HWP is not using correct limits. In HWP case driver
doesn't do anything other than setting this MSR.
When she means print correct MSR, is that when changing the mode from
powersave to peformance, when she prints MSRs (rdmsr 0x774), this
doesn't have correct max limit.
> 
> >> For more information on the MSR values for SKL please visit
> >> ISDM under Managing HWP.
> >>
> >> Signed-off-by: Alexandra Yates <alexandra.yates@linux.intel.com>
> >
> > Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> >>
> >> ---
> >>   drivers/cpufreq/intel_pstate.c | 2 ++
> >>   1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/cpufreq/intel_pstate.c
> >> b/drivers/cpufreq/intel_pstate.c
> >> index 2e31d09..0eeb7da 100644
> >> --- a/drivers/cpufreq/intel_pstate.c
> >> +++ b/drivers/cpufreq/intel_pstate.c
> >> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct
> >> cpufreq_policy *policy)
> >>             policy->max >= policy->cpuinfo.max_freq) {
> >>                 pr_debug("intel_pstate: set performance\n");
> >>                 limits = &performance_limits;
> >> +               if (hwp_active)
> >> +                       intel_pstate_hwp_set();
> 
> Honestly, I'm not really sure how this is matching the changelog.
> 
> What it does is to ensure that the correct limits are used when in the
> HWP mode too as far as I can say.  Is my understanding correct here?
Yes.
> 
> >>                 return 0;
> >>         }
> >>
> >>
> > --
> 
> Thanks,
> Rafael
> --
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Rafael J. Wysocki]

On Monday, November 23, 2015 05:17:36 PM Srinivas Pandruvada wrote:
> On Tue, 2015-11-24 at 02:09 +0100, Rafael J. Wysocki wrote:
> > Hi,
> > 
> > On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >

[cut]

> > 
> > >> For more information on the MSR values for SKL please visit
> > >> ISDM under Managing HWP.
> > >>
> > >> Signed-off-by: Alexandra Yates <alexandra.yates@linux.intel.com>
> > >
> > > Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> > >>
> > >> ---
> > >>   drivers/cpufreq/intel_pstate.c | 2 ++
> > >>   1 file changed, 2 insertions(+)
> > >>
> > >> diff --git a/drivers/cpufreq/intel_pstate.c
> > >> b/drivers/cpufreq/intel_pstate.c
> > >> index 2e31d09..0eeb7da 100644
> > >> --- a/drivers/cpufreq/intel_pstate.c
> > >> +++ b/drivers/cpufreq/intel_pstate.c
> > >> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct
> > >> cpufreq_policy *policy)
> > >>             policy->max >= policy->cpuinfo.max_freq) {
> > >>                 pr_debug("intel_pstate: set performance\n");
> > >>                 limits = &performance_limits;
> > >> +               if (hwp_active)
> > >> +                       intel_pstate_hwp_set();
> > 
> > Honestly, I'm not really sure how this is matching the changelog.
> > 
> > What it does is to ensure that the correct limits are used when in the
> > HWP mode too as far as I can say.  Is my understanding correct here?
> Yes.

OK

But if we make the "performance" limits take effect here, it will effectively
make HWP use min = max = 100%, right?  Is that what we want to happen here?

Thanks,
Rafael

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Srinivas Pandruvada]

On Tue, 2015-11-24 at 15:28 +0100, Rafael J. Wysocki wrote:
> On Monday, November 23, 2015 05:17:36 PM Srinivas Pandruvada wrote:
> > On Tue, 2015-11-24 at 02:09 +0100, Rafael J. Wysocki wrote:
> > > Hi,
> > > 
> > > On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
> > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > 
> 
> [cut]
> 
> > > 
> > > > > For more information on the MSR values for SKL please visit
> > > > > ISDM under Managing HWP.
> > > > > 
> > > > > Signed-off-by: Alexandra Yates <
> > > > > alexandra.yates@linux.intel.com>
> > > > 
> > > > Acked-by: Srinivas Pandruvada <
> > > > srinivas.pandruvada@linux.intel.com>
> > > > > 
> > > > > ---
> > > > >   drivers/cpufreq/intel_pstate.c | 2 ++
> > > > >   1 file changed, 2 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > > > b/drivers/cpufreq/intel_pstate.c
> > > > > index 2e31d09..0eeb7da 100644
> > > > > --- a/drivers/cpufreq/intel_pstate.c
> > > > > +++ b/drivers/cpufreq/intel_pstate.c
> > > > > @@ -1242,6 +1242,8 @@ static int
> > > > > intel_pstate_set_policy(struct
> > > > > cpufreq_policy *policy)
> > > > >             policy->max >= policy->cpuinfo.max_freq) {
> > > > >                 pr_debug("intel_pstate: set performance\n");
> > > > >                 limits = &performance_limits;
> > > > > +               if (hwp_active)
> > > > > +                       intel_pstate_hwp_set();
> > > 
> > > Honestly, I'm not really sure how this is matching the changelog.
> > > 
> > > What it does is to ensure that the correct limits are used when
> > > in the
> > > HWP mode too as far as I can say.  Is my understanding correct
> > > here?
> > Yes.
> 
> OK
> 
> But if we make the "performance" limits take effect here, it will
> effectively
> make HWP use min = max = 100%, right?  Is that what we want to happen
> here?
Yes. intel_pstate_hwp_set() uses limits->min_perf_pct and limits
->max_perf_pct to set HWP limits. Here these will be set to 100%.

Thanks,
Srinivas

> 
> Thanks,
> Rafael
> 

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Srinivas Pandruvada]

On Tue, 2015-11-24 at 17:36 +0100, Rafael J. Wysocki wrote:
> On Tuesday, November 24, 2015 07:57:42 AM Srinivas Pandruvada wrote:
> > On Tue, 2015-11-24 at 15:28 +0100, Rafael J. Wysocki wrote:
> > > On Monday, November 23, 2015 05:17:36 PM Srinivas Pandruvada
> > > wrote:
> > > > On Tue, 2015-11-24 at 02:09 +0100, Rafael J. Wysocki wrote:
> > > > > Hi,
> > > > > 
> > > > > On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
> > > > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > > > 
> > > 
> > > [cut]
> > > 
> > > > > 
> > > > > > > For more information on the MSR values for SKL please
> > > > > > > visit
> > > > > > > ISDM under Managing HWP.
> > > > > > > 
> > > > > > > Signed-off-by: Alexandra Yates <
> > > > > > > alexandra.yates@linux.intel.com>
> > > > > > 
> > > > > > Acked-by: Srinivas Pandruvada <
> > > > > > srinivas.pandruvada@linux.intel.com>
> > > > > > > 
> > > > > > > ---
> > > > > > >   drivers/cpufreq/intel_pstate.c | 2 ++
> > > > > > >   1 file changed, 2 insertions(+)
> > > > > > > 
> > > > > > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > > > > > b/drivers/cpufreq/intel_pstate.c
> > > > > > > index 2e31d09..0eeb7da 100644
> > > > > > > --- a/drivers/cpufreq/intel_pstate.c
> > > > > > > +++ b/drivers/cpufreq/intel_pstate.c
> > > > > > > @@ -1242,6 +1242,8 @@ static int
> > > > > > > intel_pstate_set_policy(struct
> > > > > > > cpufreq_policy *policy)
> > > > > > >             policy->max >= policy->cpuinfo.max_freq) {
> > > > > > >                 pr_debug("intel_pstate: set
> > > > > > > performance\n");
> > > > > > >                 limits = &performance_limits;
> > > > > > > +               if (hwp_active)
> > > > > > > +                       intel_pstate_hwp_set();
> > > > > 
> > > > > Honestly, I'm not really sure how this is matching the
> > > > > changelog.
> > > > > 
> > > > > What it does is to ensure that the correct limits are used
> > > > > when
> > > > > in the
> > > > > HWP mode too as far as I can say.  Is my understanding
> > > > > correct
> > > > > here?
> > > > Yes.
> > > 
> > > OK
> > > 
> > > But if we make the "performance" limits take effect here, it will
> > > effectively
> > > make HWP use min = max = 100%, right?  Is that what we want to
> > > happen
> > > here?
> > Yes. intel_pstate_hwp_set() uses limits->min_perf_pct and limits
> > ->max_perf_pct to set HWP limits. Here these will be set to 100%.
> 
> OK, so that's the intended behavior of "performance" in the HWP case,
> right?
> 
Yes.
> I'll apply this patch, but I'm going to write a new changelog for it,
> then.
Sure.

Thanks,
Srinivas

> 
> Thanks,
> Rafael
> 

Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors

[Rafael J. Wysocki]

On Tuesday, November 24, 2015 07:57:42 AM Srinivas Pandruvada wrote:
> On Tue, 2015-11-24 at 15:28 +0100, Rafael J. Wysocki wrote:
> > On Monday, November 23, 2015 05:17:36 PM Srinivas Pandruvada wrote:
> > > On Tue, 2015-11-24 at 02:09 +0100, Rafael J. Wysocki wrote:
> > > > Hi,
> > > > 
> > > > On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada
> > > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > > 
> > 
> > [cut]
> > 
> > > > 
> > > > > > For more information on the MSR values for SKL please visit
> > > > > > ISDM under Managing HWP.
> > > > > > 
> > > > > > Signed-off-by: Alexandra Yates <
> > > > > > alexandra.yates@linux.intel.com>
> > > > > 
> > > > > Acked-by: Srinivas Pandruvada <
> > > > > srinivas.pandruvada@linux.intel.com>
> > > > > > 
> > > > > > ---
> > > > > >   drivers/cpufreq/intel_pstate.c | 2 ++
> > > > > >   1 file changed, 2 insertions(+)
> > > > > > 
> > > > > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > > > > b/drivers/cpufreq/intel_pstate.c
> > > > > > index 2e31d09..0eeb7da 100644
> > > > > > --- a/drivers/cpufreq/intel_pstate.c
> > > > > > +++ b/drivers/cpufreq/intel_pstate.c
> > > > > > @@ -1242,6 +1242,8 @@ static int
> > > > > > intel_pstate_set_policy(struct
> > > > > > cpufreq_policy *policy)
> > > > > >             policy->max >= policy->cpuinfo.max_freq) {
> > > > > >                 pr_debug("intel_pstate: set performance\n");
> > > > > >                 limits = &performance_limits;
> > > > > > +               if (hwp_active)
> > > > > > +                       intel_pstate_hwp_set();
> > > > 
> > > > Honestly, I'm not really sure how this is matching the changelog.
> > > > 
> > > > What it does is to ensure that the correct limits are used when
> > > > in the
> > > > HWP mode too as far as I can say.  Is my understanding correct
> > > > here?
> > > Yes.
> > 
> > OK
> > 
> > But if we make the "performance" limits take effect here, it will
> > effectively
> > make HWP use min = max = 100%, right?  Is that what we want to happen
> > here?
> Yes. intel_pstate_hwp_set() uses limits->min_perf_pct and limits
> ->max_perf_pct to set HWP limits. Here these will be set to 100%.

OK, so that's the intended behavior of "performance" in the HWP case, right?

I'll apply this patch, but I'm going to write a new changelog for it, then.

Thanks,
Rafael