RE: [PATCH] cpufreq: intel_pstate: Fix cpuinfo_cur_freq after performance governor changes

[Huaisheng HS1 Ye]

Hi Srinivas,
Your idea is great, but your patch at cpufreq.c will force all platforms to use scaling_cur_freq as first choice when userspace wants to access cpuinfo_cur_freq. It is ok for intel x86 platfrom but hard to say with other platforms.
I modified it like that, it looks more reasonable. How about that?

Hi Rafael,
Deleting "get" function pointer within intel_pstate would lead to sysfs interface cpuinfo_cur_freq disappearing, because of cpufreq_add_dev_interface will check "cpufreq_driver->get" for it.
Perhaps just return 0 with in intel_pstate_get would be a workaround for this issue, how about it?

I have tested this patch based on Purley platform, both Hardware and Software P-states works correct, we could get accurate and same frequency from cpuinfo_cur_freq and scaling_cur_freq.

 drivers/cpufreq/cpufreq.c      | 4 ++++
 drivers/cpufreq/intel_pstate.c | 8 +++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 9bf97a3..922f9d9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -694,6 +694,10 @@ static ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,
 	if (cur_freq)
 		return sprintf(buf, "%u\n", cur_freq);
 
+	cur_freq = arch_freq_get_on_cpu(policy->cpu);
+	if (cur_freq)
+		return sprintf(buf, "%u\n", cur_freq);
+
 	return sprintf(buf, "<unknown>\n");
 }
 
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 6cd5035..33e6c10 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1924,9 +1924,11 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
 
 static unsigned int intel_pstate_get(unsigned int cpu_num)
 {
-	struct cpudata *cpu = all_cpu_data[cpu_num];
-
-	return cpu ? get_avg_frequency(cpu) : 0;
+	/*
+	 * Use frequency from scaling_cur_freq, reserve this function
+	 * for existing of sysfs cpuinfo_cur_freq.
+	 */
+	return 0;
 }
 
 static void intel_pstate_set_update_util_hook(unsigned int cpu_num)


> On Tue, 2017-07-25 at 01:46 +0000, Huaisheng HS1 Ye wrote:
> > Hi Rafael,
> >
> > If you delete "get" function implement within intel_pstate, the sysfs
> > interface cpuinfo_cur_freq will display <unknown> all the time.
> cpuinfo_cur_freq by definition should show actual frequency HW frequency.
> Unless I missed something. So Len Brown's patch should also take care of this
> to get from arch specific function is available.
> So in addition to Rafael's change, what about this?
> 
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index
> 9bf97a3..29ec687 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -689,8 +689,13 @@ store_one(scaling_max_freq, max);
> Âstatic ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,
> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂchar *buf)
> Â{
> -ÂÂÂÂÂÂÂunsigned int cur_freq = __cpufreq_get(policy);
> +ÂÂÂÂÂÂÂunsigned int cur_freq;
> 
> +ÂÂÂÂÂÂÂcur_freq = arch_freq_get_on_cpu(policy->cpu);
> +ÂÂÂÂÂÂÂif (cur_freq)
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂreturn sprintf(buf, "%u\n", cur_freq);
> +
> +ÂÂÂÂÂÂÂcur_freq = __cpufreq_get(policy);
> ÂÂÂÂÂÂÂÂif (cur_freq)
> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂreturn sprintf(buf, "%u\n", cur_freq);
> 
> 
> 
> Thanks,
> Srinivas
> 
> > To be honest, at the beginning I have consider this way like you
> > patched, but based two reasons below, it is conservative for us to do
> > that.
> >
> > 1. I am worried about whether it would lead to confusion for customers
> > or Linux OS venders who are accustomed to cpuinfo_cur_freq.
> > 2. This is the first time for me to offer patch to intel_pstate, not
> > sure whether it could be accepted by you.
> >
> > >
> > > On Monday, July 24, 2017 03:32:47 PM Huaisheng HS1 Ye wrote:
> > > >
> > > > Hi Rafael,
> > > > Thanks for your reply.
> > > >
> > > > >
> > > > > On Monday, July 24, 2017 05:43:14 AM Huaisheng HS1 Ye wrote:
> > > > > >
> > > > > > After commit 82b4e03e01bc (intel_pstate: skip scheduler hook
> > > > > > when in "performance" mode) Software P-state control modes
> > > > > > couldn't get dynamic value during performance mode,
> > > > > Please explain what you mean here.
> > > > >
> > > > commit 82b4e03e01bc (intel_pstate: skip scheduler hook when in
> > > > "performance" mode) disables intel_pstate_set_update_util_hook
> > > > when current policy is performance within function
> > > > intel_pstate_set_policy.
> > > > It leads to Software P-states couldn't update sysfs interface
> > > > cpuinfo_cur_freq's value during performance mode, because of
> > > > pstate_funcs.update_util couldn't set for the given CPU.
> > > >
> > > > >
> > > > > I guess you carried out some tests and the results were not as
> > > > > expected, so what was the test?
> > > > Exactly, we check the sysfs interface cpuinfo_cur_freq and the
> > > > output of cpupower frequency-info both with performance mode.
> > > OK, so what about the change below:
> > >
> > > ---
> > > Âdrivers/cpufreq/intel_pstate.c |ÂÂÂÂ8 --------
> > > Â1 file changed, 8 deletions(-)
> > >
> > > Index: linux-pm/drivers/cpufreq/intel_pstate.c
> > >
> ==============================================================
> > > =====
> > > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> > > +++ linux-pm/drivers/cpufreq/intel_pstate.c
> > > @@ -1674,13 +1674,6 @@ static int intel_pstate_init_cpu(unsigne
> > > Â	return 0;
> > > Â}
> > >
> > > -static unsigned int intel_pstate_get(unsigned int cpu_num) -{
> > > -	struct cpudata *cpu = all_cpu_data[cpu_num];
> > > -
> > > -	return cpu ? get_avg_frequency(cpu) : 0;
> > > -}
> > > -
> > > Âstatic void intel_pstate_set_update_util_hook(unsigned int
> > > cpu_num)ÂÂ{
> > > Â	struct cpudata *cpu = all_cpu_data[cpu_num]; @@ -1921,7
> > > +1914,6 @@
> > > static struct cpufreq_driver intel_pstat
> > > Â	.setpolicy	= intel_pstate_set_policy,
> > > Â	.suspend	= intel_pstate_hwp_save_state,
> > > Â	.resume		= intel_pstate_resume,
> > > -	.get		= intel_pstate_get,
> > > Â	.init		= intel_pstate_cpu_init,
> > > Â	.exit		= intel_pstate_cpu_exit,
> > > Â	.stop_cpu	= intel_pstate_stop_cpu,