Commit bc3b6562 authored by Ionela Voinescu's avatar Ionela Voinescu Committed by Catalin Marinas
Browse files

arm64: split counter validation function 



In order for the counter validation function to be reused, split
validate_cpu_freq_invariance_counters() into:
 - freq_counters_valid(cpu) - check cpu for valid cycle counters
 - freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate) -
   generic function that sets the normalization ratio used by
   topology_scale_freq_tick()

Signed-off-by: default avatarIonela Voinescu <ionela.voinescu@arm.com>
Reviewed-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201106125334.21570-3-ionela.voinescu@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 4b9cf23c

arch/arm64/kernel/topology.c

+26 −18
Original line number Diff line number Diff line
@@ -145,45 +145,49 @@ void update_freq_counters_refs(void) 
	this_cpu_write(arch_const_cycles_prev, read_constcnt());

}



static int validate_cpu_freq_invariance_counters(int cpu)

static inline bool freq_counters_valid(int cpu)

{

	u64 max_freq_hz, ratio;



	if (!cpu_has_amu_feat(cpu)) {

		pr_debug("CPU%d: counters are not supported.\n", cpu);

		return -EINVAL;

		return false;

	}



	if (unlikely(!per_cpu(arch_const_cycles_prev, cpu) ||

		     !per_cpu(arch_core_cycles_prev, cpu))) {

		pr_debug("CPU%d: cycle counters are not enabled.\n", cpu);

		return -EINVAL;

		return false;

	}



	/* Convert maximum frequency from KHz to Hz and validate */

	max_freq_hz = cpufreq_get_hw_max_freq(cpu) * 1000;

	if (unlikely(!max_freq_hz)) {

		pr_debug("CPU%d: invalid maximum frequency.\n", cpu);

	return true;

}



static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)

{

	u64 ratio;



	if (unlikely(!max_rate || !ref_rate)) {

		pr_debug("CPU%d: invalid maximum or reference frequency.\n",

			 cpu);

		return -EINVAL;

	}



	/*

	 * Pre-compute the fixed ratio between the frequency of the constant

	 * counter and the maximum frequency of the CPU.

	 * reference counter and the maximum frequency of the CPU.

	 *

	 *			      const_freq

	 * arch_max_freq_scale =   ---------------- * SCHED_CAPACITY_SCALE²

	 *			   cpuinfo_max_freq

	 *			    ref_rate

	 * arch_max_freq_scale =   ---------- * SCHED_CAPACITY_SCALE²

	 *			    max_rate

	 *

	 * We use a factor of 2 * SCHED_CAPACITY_SHIFT -> SCHED_CAPACITY_SCALE²

	 * in order to ensure a good resolution for arch_max_freq_scale for

	 * very low arch timer frequencies (down to the KHz range which should

	 * very low reference frequencies (down to the KHz range which should

	 * be unlikely).

	 */

	ratio = (u64)arch_timer_get_rate() << (2 * SCHED_CAPACITY_SHIFT);

	ratio = div64_u64(ratio, max_freq_hz);

	ratio = ref_rate << (2 * SCHED_CAPACITY_SHIFT);

	ratio = div64_u64(ratio, max_rate);

	if (!ratio) {

		WARN_ONCE(1, "System timer frequency too low.\n");

		WARN_ONCE(1, "Reference frequency too low.\n");

		return -EINVAL;

	}
@@ -230,8 +234,12 @@ static int __init init_amu_fie(void) 
	}



	for_each_present_cpu(cpu) {

		if (validate_cpu_freq_invariance_counters(cpu))

		if (!freq_counters_valid(cpu) ||

		    freq_inv_set_max_ratio(cpu,

					   cpufreq_get_hw_max_freq(cpu) * 1000,

					   arch_timer_get_rate()))

			continue;



		cpumask_set_cpu(cpu, valid_cpus);

		have_policy |= enable_policy_freq_counters(cpu, valid_cpus);

	}