[2/4] arm64: wrap and generalise counter read functions

Commit Message

Ionela Voinescu Aug. 26, 2020, 1:03 p.m. UTC

In preparation for other uses of Activity Monitors (AMU) cycle counters,
place counter read functionality in generic functions that can reused:
read_corecnt() and read_constcnt().

As a result, implement update_freq_counters_refs() to replace
init_cpu_freq_invariance_counters() and both initialise and update
the per-cpu reference variables.

Signed-off-by: Ionela Voinescu <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Will Deacon <[e-mail]>
---
 arch/arm64/kernel/cpufeature.c |  4 ++--
 arch/arm64/kernel/topology.c   | 36 ++++++++++++++++++++++------------
 2 files changed, 26 insertions(+), 14 deletions(-)

Comments

Valentin Schneider Aug. 27, 2020, 9:30 a.m. UTC | #1

On 27/08/20 04:36, kernel test robot wrote:
>    In file included from include/linux/energy_model.h:10,
>                     from include/linux/device.h:16,
>                     from include/linux/acpi.h:15,
>                     from arch/arm64/kernel/topology.c:14:
>    include/linux/sched/topology.h:40:3: warning: 'sd_flag_debug' defined but not used [-Wunused-const-variable=]
>       40 | } sd_flag_debug[] = {
>          |   ^~~~~~~~~~~~~
>    In file included from include/linux/energy_model.h:10,
>                     from include/linux/device.h:16,
>                     from include/linux/acpi.h:15,
>                     from arch/arm64/kernel/topology.c:14:
>    include/linux/sched/topology.h:30:27: warning: 'SD_DEGENERATE_GROUPS_MASK' defined but not used [-Wunused-const-variable=]
>       30 | static const unsigned int SD_DEGENERATE_GROUPS_MASK =
>          |                           ^~~~~~~~~~~~~~~~~~~~~~~~~
>

Sorry about those, should be gone in latest tip/sched/core.

Patch

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 15a376689b2f..40d7a4c52558 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1522,7 +1522,7 @@  const struct cpumask *cpus_with_amu_counters(void)
 }
 
 /* Initialize the use of AMU counters for frequency invariance */
-extern void init_cpu_freq_invariance_counters(void);
+extern void update_freq_counters_refs(void);
 
 static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap)
 {
@@ -1530,7 +1530,7 @@  static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap)
 		pr_info("detected CPU%d: Activity Monitors Unit (AMU)\n",
 			smp_processor_id());
 		cpumask_set_cpu(smp_processor_id(), &amu_cpus);
-		init_cpu_freq_invariance_counters();
+		update_freq_counters_refs();
 	}
 }
 
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 2ef440938282..1241087e92c8 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -121,23 +121,33 @@  int __init parse_acpi_topology(void)
 }
 #endif
 
-#ifdef CONFIG_ARM64_AMU_EXTN
+#define COUNTER_READ_STORE(NAME, VAL) \
+static inline u64 read_##NAME(void) \
+{ \
+	return VAL; \
+} \
+static inline void store_##NAME(void *val) \
+{ \
+	*(u64 *)val = read_##NAME(); \
+}
 
-#undef pr_fmt
-#define pr_fmt(fmt) "AMU: " fmt
+#ifdef CONFIG_ARM64_AMU_EXTN
+COUNTER_READ_STORE(corecnt, read_sysreg_s(SYS_AMEVCNTR0_CORE_EL0));
+COUNTER_READ_STORE(constcnt, read_sysreg_s(SYS_AMEVCNTR0_CONST_EL0));
+#else
+COUNTER_READ_STORE(corecnt, 0);
+COUNTER_READ_STORE(constcnt, 0);
+#endif
 
 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;
 
-/* Initialize counter reference per-cpu variables for the current CPU */
-void init_cpu_freq_invariance_counters(void)
+void update_freq_counters_refs(void)
 {
-	this_cpu_write(arch_core_cycles_prev,
-		       read_sysreg_s(SYS_AMEVCNTR0_CORE_EL0));
-	this_cpu_write(arch_const_cycles_prev,
-		       read_sysreg_s(SYS_AMEVCNTR0_CONST_EL0));
+	this_cpu_write(arch_core_cycles_prev, read_corecnt());
+	this_cpu_write(arch_const_cycles_prev, read_constcnt());
 }
 
 static int validate_cpu_freq_invariance_counters(int cpu)
@@ -272,11 +282,14 @@  void topology_scale_freq_tick(void)
 	if (!cpumask_test_cpu(cpu, amu_fie_cpus))
 		return;
 
-	const_cnt = read_sysreg_s(SYS_AMEVCNTR0_CONST_EL0);
-	core_cnt = read_sysreg_s(SYS_AMEVCNTR0_CORE_EL0);
 	prev_const_cnt = this_cpu_read(arch_const_cycles_prev);
 	prev_core_cnt = this_cpu_read(arch_core_cycles_prev);
 
+	update_freq_counters_refs();
+
+	const_cnt = this_cpu_read(arch_const_cycles_prev);
+	core_cnt = this_cpu_read(arch_core_cycles_prev);
+
 	if (unlikely(core_cnt <= prev_core_cnt ||
 		     const_cnt <= prev_const_cnt))
 		goto store_and_exit;
@@ -301,4 +314,3 @@  void topology_scale_freq_tick(void)
 	this_cpu_write(arch_core_cycles_prev, core_cnt);
 	this_cpu_write(arch_const_cycles_prev, const_cnt);
 }
-#endif /* CONFIG_ARM64_AMU_EXTN */