[RFC 1/3] arm64: topology: Add amu_counters_supported() helper

[Viresh Kumar]

We would need to know earlier during the boot cycle if AMUs are
supported or not for all the CPUs, export a routine for that and move
code around to make it more readable.

Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
---
 arch/arm64/kernel/topology.c | 108 ++++++++++++++++++-----------------
 1 file changed, 56 insertions(+), 52 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index b7da372819fc..74fde35b56ef 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -130,6 +130,9 @@ static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale);
 static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
 static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
 static cpumask_var_t amu_fie_cpus;
+static cpumask_var_t valid_cpus;
+static DEFINE_STATIC_KEY_FALSE(amu_fie_key);
+#define amu_freq_invariant() static_branch_unlikely(&amu_fie_key)
 
 /* Initialize counter reference per-cpu variables for the current CPU */
 void init_cpu_freq_invariance_counters(void)
@@ -140,26 +143,14 @@ void init_cpu_freq_invariance_counters(void)
 		       read_sysreg_s(SYS_AMEVCNTR0_CONST_EL0));
 }
 
-static int validate_cpu_freq_invariance_counters(int cpu)
+static void setup_freq_invariance(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;
-	}
-
-	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;
-	}
+	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+	u64 ratio;
 
-	/* 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 -EINVAL;
+	if (!policy) {
+		pr_debug("CPU%d: No cpufreq policy found.\n", cpu);
+		return;
 	}
 
 	/*
@@ -176,69 +167,75 @@ static int validate_cpu_freq_invariance_counters(int cpu)
 	 * be unlikely).
 	 */
 	ratio = (u64)arch_timer_get_rate() << (2 * SCHED_CAPACITY_SHIFT);
-	ratio = div64_u64(ratio, max_freq_hz);
+	ratio = div64_u64(ratio, policy->cpuinfo.max_freq * 1000);
 	if (!ratio) {
 		WARN_ONCE(1, "System timer frequency too low.\n");
-		return -EINVAL;
+		goto out;
 	}
 
 	per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
 
-	return 0;
-}
-
-static inline void update_amu_fie_cpus(int cpu, cpumask_var_t valid_cpus)
-{
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-
-	if (!policy) {
-		pr_debug("CPU%d: No cpufreq policy found.\n", cpu);
-		return;
-	}
-
 	if (cpumask_subset(policy->related_cpus, valid_cpus))
-		cpumask_or(amu_fie_cpus, policy->related_cpus,
-			   amu_fie_cpus);
+		cpumask_or(amu_fie_cpus, policy->related_cpus, amu_fie_cpus);
 
+out:
 	cpufreq_cpu_put(policy);
 }
 
-static DEFINE_STATIC_KEY_FALSE(amu_fie_key);
-#define amu_freq_invariant() static_branch_unlikely(&amu_fie_key)
+bool amu_counters_supported(void)
+{
+	return likely(cpumask_available(valid_cpus)) &&
+		cpumask_equal(valid_cpus, cpu_present_mask);
+}
 
-static int __init init_amu_fie(void)
+static int __init early_init_amu_fie(void)
 {
-	cpumask_var_t valid_cpus;
-	int ret = 0;
 	int cpu;
 
 	if (!zalloc_cpumask_var(&valid_cpus, GFP_KERNEL))
 		return -ENOMEM;
 
-	if (!zalloc_cpumask_var(&amu_fie_cpus, GFP_KERNEL)) {
-		ret = -ENOMEM;
-		goto free_valid_mask;
-	}
-
 	for_each_present_cpu(cpu) {
-		if (validate_cpu_freq_invariance_counters(cpu))
+		if (!cpu_has_amu_feat(cpu)) {
+			pr_debug("CPU%d: counters are not supported.\n", cpu);
+			continue;
+		}
+
+		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);
 			continue;
+		}
+
 		cpumask_set_cpu(cpu, valid_cpus);
-		update_amu_fie_cpus(cpu, valid_cpus);
 	}
 
+	return 0;
+}
+core_initcall_sync(early_init_amu_fie);
+
+static int __init late_init_amu_fie(void)
+{
+	int cpu;
+
+	if (!cpumask_available(valid_cpus))
+		return -ENOMEM;
+
+	if (!zalloc_cpumask_var(&amu_fie_cpus, GFP_KERNEL))
+		return -ENOMEM;
+
+	for_each_present_cpu(cpu)
+		setup_freq_invariance(cpu);
+
 	if (!cpumask_empty(amu_fie_cpus)) {
 		pr_info("CPUs[%*pbl]: counters will be used for FIE.",
 			cpumask_pr_args(amu_fie_cpus));
 		static_branch_enable(&amu_fie_key);
 	}
 
-free_valid_mask:
-	free_cpumask_var(valid_cpus);
-
-	return ret;
+	return 0;
 }
-late_initcall_sync(init_amu_fie);
+late_initcall_sync(late_init_amu_fie);
 
 bool arch_freq_counters_available(struct cpumask *cpus)
 {
@@ -272,7 +269,7 @@ void topology_scale_freq_tick(void)
 	 * scale =  ------- * --------------------
 	 *	    /\const   SCHED_CAPACITY_SCALE
 	 *
-	 * See validate_cpu_freq_invariance_counters() for details on
+	 * See setup_freq_invariance() for details on
 	 * arch_max_freq_scale and the use of SCHED_CAPACITY_SHIFT.
 	 */
 	scale = core_cnt - prev_core_cnt;
@@ -287,4 +284,11 @@ void topology_scale_freq_tick(void)
 	this_cpu_write(arch_core_cycles_prev, core_cnt);
 	this_cpu_write(arch_const_cycles_prev, const_cnt);
 }
+#else
+bool amu_counters_supported(void)
+{
+	return false;
+}
 #endif /* CONFIG_ARM64_AMU_EXTN */
+
+EXPORT_SYMBOL_GPL(amu_counters_supported);
-- 
2.25.0.rc1.19.g042ed3e048af