linux-kernel - Re: [PATCH 4/5] intel_pstate: Remove C0 tracking

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Date:	Mon, 12 May 2014 02:26:16 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	dirk.brandewie@...il.com
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH 4/5] intel_pstate: Remove C0 tracking

On Thursday, May 08, 2014 12:57:26 PM dirk.brandewie@...il.com wrote:
> From: Dirk Brandewie <dirk.j.brandewie@...el.com>
> 
> Commit fcb6a15c intel_pstate: Take core C0 time into account for core busy
> introduced a regression referenced below.  The issue with "lockup"
> after suspend that this commit was addressing is now dealt with in the
> suspend path.
> 
> References:
>    https://bugzilla.kernel.org/show_bug.cgi?id=66581
>    https://bugzilla.kernel.org/show_bug.cgi?id=75121
> 
> Reported-by: Doug Smythies <dsmythies@...us.net>
> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>

Do we need this in -stable?

> ---
>  drivers/cpufreq/intel_pstate.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index bb20881..4c26faf 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -59,7 +59,6 @@ struct sample {
>  	int32_t core_pct_busy;
>  	u64 aperf;
>  	u64 mperf;
> -	unsigned long long tsc;
>  	int freq;
>  };
>  
> @@ -100,7 +99,6 @@ struct cpudata {
>  
>  	u64	prev_aperf;
>  	u64	prev_mperf;
> -	unsigned long long prev_tsc;
>  	struct sample sample;
>  };
>  
> @@ -561,46 +559,37 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu,
>  					struct sample *sample)
>  {
>  	int32_t core_pct;
> -	int32_t c0_pct;
>  
>  	core_pct = div_fp(int_tofp((sample->aperf)),
>  			int_tofp((sample->mperf)));
>  	core_pct = mul_fp(core_pct, int_tofp(100));
>  	FP_ROUNDUP(core_pct);
>  
> -	c0_pct = div_fp(int_tofp(sample->mperf), int_tofp(sample->tsc));
> -
>  	sample->freq = fp_toint(
>  		mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
>  
> -	sample->core_pct_busy = mul_fp(core_pct, c0_pct);
> +	sample->core_pct_busy = core_pct;
>  }
>  
>  static inline void intel_pstate_sample(struct cpudata *cpu)
>  {
>  	u64 aperf, mperf;
> -	unsigned long long tsc;
>  
>  	rdmsrl(MSR_IA32_APERF, aperf);
>  	rdmsrl(MSR_IA32_MPERF, mperf);
> -	tsc = native_read_tsc();
>  
>  	aperf = aperf >> FRAC_BITS;
>  	mperf = mperf >> FRAC_BITS;
> -	tsc = tsc >> FRAC_BITS;
>  
>  	cpu->sample.aperf = aperf;
>  	cpu->sample.mperf = mperf;
> -	cpu->sample.tsc = tsc;
>  	cpu->sample.aperf -= cpu->prev_aperf;
>  	cpu->sample.mperf -= cpu->prev_mperf;
> -	cpu->sample.tsc -= cpu->prev_tsc;
>  
>  	intel_pstate_calc_busy(cpu, &cpu->sample);
>  
>  	cpu->prev_aperf = aperf;
>  	cpu->prev_mperf = mperf;
> -	cpu->prev_tsc = tsc;
>  }
>  
>  static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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