powerpc/sysfs: Show idle_purr and idle_spurr for every CPU

On Pseries LPARs, to calculate utilization, we need to know the
[S]PURR ticks when the CPUs were busy or idle.

The total PURR and SPURR ticks are already exposed via the per-cpu
sysfs files "purr" and "spurr". This patch adds support for exposing
the idle PURR and SPURR ticks via new per-cpu sysfs files named
"idle_purr" and "idle_spurr".

This patch also adds helper functions to accurately read the values of
idle_purr and idle_spurr especially from an interrupt context between
when the interrupt has occurred between the pseries_idle_prolog() and
pseries_idle_epilog(). This will ensure that the idle purr/spurr
values corresponding to the latest idle period is accounted for before
these values are read.
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1586249263-14048-5-git-send-email-ego@linux.vnet.ibm.com

arch/powerpc/include/asm/idle.h

@@ -57,5 +57,37 @@ static inline void pseries_idle_epilog(void)
 	ppc64_runlatch_on();
 }
 
+static inline u64 read_this_idle_purr(void)
+{
+	/*
+	 * If we are reading from an idle context, update the
+	 * idle-purr cycles corresponding to the last idle period.
+	 * Since the idle context is not yet over, take a fresh
+	 * snapshot of the idle-purr.
+	 */
+	if (unlikely(get_lppaca()->idle == 1)) {
+		update_idle_purr_accounting();
+		snapshot_purr_idle_entry();
+	}
+
+	return be64_to_cpu(get_lppaca()->wait_state_cycles);
+}
+
+static inline u64 read_this_idle_spurr(void)
+{
+	/*
+	 * If we are reading from an idle context, update the
+	 * idle-spurr cycles corresponding to the last idle period.
+	 * Since the idle context is not yet over, take a fresh
+	 * snapshot of the idle-spurr.
+	 */
+	if (get_lppaca()->idle == 1) {
+		update_idle_spurr_accounting();
+		snapshot_spurr_idle_entry();
+	}
+
+	return *this_cpu_ptr(&idle_spurr_cycles);
+}
+
 #endif /* CONFIG_PPC_PSERIES */
 #endif

arch/powerpc/kernel/sysfs.c

@@ -19,6 +19,7 @@
 #include <asm/smp.h>
 #include <asm/pmc.h>
 #include <asm/firmware.h>
+#include <asm/idle.h>
 #include <asm/svm.h>
 
 #include "cacheinfo.h"
@@ -760,6 +761,74 @@ static void create_svm_file(void)
 }
 #endif /* CONFIG_PPC_SVM */
 
+#ifdef CONFIG_PPC_PSERIES
+static void read_idle_purr(void *val)
+{
+	u64 *ret = val;
+
+	*ret = read_this_idle_purr();
+}
+
+static ssize_t idle_purr_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	u64 val;
+
+	smp_call_function_single(cpu->dev.id, read_idle_purr, &val, 1);
+	return sprintf(buf, "%llx\n", val);
+}
+static DEVICE_ATTR(idle_purr, 0400, idle_purr_show, NULL);
+
+static void create_idle_purr_file(struct device *s)
+{
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		device_create_file(s, &dev_attr_idle_purr);
+}
+
+static void remove_idle_purr_file(struct device *s)
+{
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		device_remove_file(s, &dev_attr_idle_purr);
+}
+
+static void read_idle_spurr(void *val)
+{
+	u64 *ret = val;
+
+	*ret = read_this_idle_spurr();
+}
+
+static ssize_t idle_spurr_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	u64 val;
+
+	smp_call_function_single(cpu->dev.id, read_idle_spurr, &val, 1);
+	return sprintf(buf, "%llx\n", val);
+}
+static DEVICE_ATTR(idle_spurr, 0400, idle_spurr_show, NULL);
+
+static void create_idle_spurr_file(struct device *s)
+{
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		device_create_file(s, &dev_attr_idle_spurr);
+}
+
+static void remove_idle_spurr_file(struct device *s)
+{
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		device_remove_file(s, &dev_attr_idle_spurr);
+}
+
+#else /* CONFIG_PPC_PSERIES */
+#define create_idle_purr_file(s)
+#define remove_idle_purr_file(s)
+#define create_idle_spurr_file(s)
+#define remove_idle_spurr_file(s)
+#endif /* CONFIG_PPC_PSERIES */
+
 static int register_cpu_online(unsigned int cpu)
 {
 	struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -823,10 +892,13 @@ static int register_cpu_online(unsigned int cpu)
 		if (!firmware_has_feature(FW_FEATURE_LPAR))
 			add_write_permission_dev_attr(&dev_attr_purr);
 		device_create_file(s, &dev_attr_purr);
+		create_idle_purr_file(s);
 	}
 
-	if (cpu_has_feature(CPU_FTR_SPURR))
+	if (cpu_has_feature(CPU_FTR_SPURR)) {
 		device_create_file(s, &dev_attr_spurr);
+		create_idle_spurr_file(s);
+	}
 
 	if (cpu_has_feature(CPU_FTR_DSCR))
 		device_create_file(s, &dev_attr_dscr);
@@ -910,11 +982,15 @@ static int unregister_cpu_online(unsigned int cpu)
 		device_remove_file(s, &dev_attr_mmcra);
 #endif /* CONFIG_PMU_SYSFS */
 
-	if (cpu_has_feature(CPU_FTR_PURR))
+	if (cpu_has_feature(CPU_FTR_PURR)) {
 		device_remove_file(s, &dev_attr_purr);
+		remove_idle_purr_file(s);
+	}
 
-	if (cpu_has_feature(CPU_FTR_SPURR))
+	if (cpu_has_feature(CPU_FTR_SPURR)) {
 		device_remove_file(s, &dev_attr_spurr);
+		remove_idle_spurr_file(s);
+	}
 
 	if (cpu_has_feature(CPU_FTR_DSCR))
 		device_remove_file(s, &dev_attr_dscr);