Commit 12f136b2 authored by Zeng Heng's avatar Zeng Heng
Browse files

cpufreq: CPPC: Keep the target core awake when reading its cpufreq rate 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I73EPL



--------------------------------

As ARM AMU's document says, all counters are subject to any changes
in clock frequency, including clock stopping caused by the WFI and WFE
instructions.

Therefore, using smp_call_on_cpu() to trigger target CPU to
read self's AMU counters, which ensures the counters are working
properly while cstate feature is enabled.

Reported-by: default avatarSumit Gupta <sumitg@nvidia.com>
Link: https://lore.kernel.org/all/20230418113459.12860-7-sumitg@nvidia.com/


Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
parent 789ca6a6

drivers/cpufreq/cppc_cpufreq.c

+30 −9
Original line number Diff line number Diff line
@@ -90,6 +90,12 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data, 
				 struct cppc_perf_fb_ctrs *fb_ctrs_t0,

				 struct cppc_perf_fb_ctrs *fb_ctrs_t1);



struct fb_ctr_pair {

	u32 cpu;

	struct cppc_perf_fb_ctrs fb_ctrs_t0;

	struct cppc_perf_fb_ctrs fb_ctrs_t1;

};



/**

 * cppc_scale_freq_workfn - CPPC arch_freq_scale updater for frequency invariance

 * @work: The work item.
@@ -840,9 +846,24 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data, 
	return (reference_perf * delta_delivered) / delta_reference;

}



static int cppc_get_perf_ctrs_pair(void *val)

{

	struct fb_ctr_pair *fb_ctrs = val;

	int cpu = fb_ctrs->cpu;

	int ret;



	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs->fb_ctrs_t0);

	if (ret)

		return ret;



	udelay(2); /* 2usec delay between sampling */



	return cppc_get_perf_ctrs(cpu, &fb_ctrs->fb_ctrs_t1);

}



static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)

{

	struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};

	struct fb_ctr_pair fb_ctrs = { .cpu = cpu, };

	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);

	struct cppc_cpudata *cpu_data = policy->driver_data;

	u64 delivered_perf;
@@ -850,18 +871,18 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) 


	cpufreq_cpu_put(policy);



	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0);

	if (ret)

		return 0;



	udelay(2); /* 2usec delay between sampling */

	if (cpu_has_amu_feat(cpu))

		ret = smp_call_on_cpu(cpu, cppc_get_perf_ctrs_pair,

				      &fb_ctrs, false);

	else

		ret = cppc_get_perf_ctrs_pair(&fb_ctrs);



	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t1);

	if (ret)

		return 0;



	delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0,

					       &fb_ctrs_t1);

	delivered_perf = cppc_perf_from_fbctrs(cpu_data,

					      &fb_ctrs.fb_ctrs_t0,

					      &fb_ctrs.fb_ctrs_t1);



	return cppc_cpufreq_perf_to_khz(cpu_data, delivered_perf);

}