cpupower: Introduce ACPI CPPC library

Kernel ACPI subsytem introduced the sysfs attributes for acpi cppc
library in below path:

/sys/devices/system/cpu/cpuX/acpi_cppc/

And these attributes will be used for AMD P-State driver to provide some
performance and frequency values.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/power/cpupower/Makefile

@@ -143,9 +143,9 @@ UTIL_HEADERS = utils/helpers/helpers.h utils/idle_monitor/cpupower-monitor.h \
 	utils/helpers/bitmask.h \
 	utils/idle_monitor/idle_monitors.h utils/idle_monitor/idle_monitors.def
 
-LIB_HEADERS = 	lib/cpufreq.h lib/cpupower.h lib/cpuidle.h
-LIB_SRC = 	lib/cpufreq.c lib/cpupower.c lib/cpuidle.c
-LIB_OBJS = 	lib/cpufreq.o lib/cpupower.o lib/cpuidle.o
+LIB_HEADERS = 	lib/cpufreq.h lib/cpupower.h lib/cpuidle.h lib/acpi_cppc.h
+LIB_SRC = 	lib/cpufreq.c lib/cpupower.c lib/cpuidle.c lib/acpi_cppc.c
+LIB_OBJS = 	lib/cpufreq.o lib/cpupower.o lib/cpuidle.o lib/acpi_cppc.o
 LIB_OBJS :=	$(addprefix $(OUTPUT),$(LIB_OBJS))
 
 override CFLAGS +=	-pipe

tools/power/cpupower/lib/acpi_cppc.c

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "cpupower_intern.h"
+#include "acpi_cppc.h"
+
+/* ACPI CPPC sysfs access ***********************************************/
+
+static int acpi_cppc_read_file(unsigned int cpu, const char *fname,
+			       char *buf, size_t buflen)
+{
+	char path[SYSFS_PATH_MAX];
+
+	snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/acpi_cppc/%s",
+		 cpu, fname);
+	return cpupower_read_sysfs(path, buf, buflen);
+}
+
+static const char * const acpi_cppc_value_files[] = {
+	[HIGHEST_PERF] = "highest_perf",
+	[LOWEST_PERF] = "lowest_perf",
+	[NOMINAL_PERF] = "nominal_perf",
+	[LOWEST_NONLINEAR_PERF] = "lowest_nonlinear_perf",
+	[LOWEST_FREQ] = "lowest_freq",
+	[NOMINAL_FREQ] = "nominal_freq",
+	[REFERENCE_PERF] = "reference_perf",
+	[WRAPAROUND_TIME] = "wraparound_time"
+};
+
+unsigned long acpi_cppc_get_data(unsigned int cpu, enum acpi_cppc_value which)
+{
+	unsigned long long value;
+	unsigned int len;
+	char linebuf[MAX_LINE_LEN];
+	char *endp;
+
+	if (which >= MAX_CPPC_VALUE_FILES)
+		return 0;
+
+	len = acpi_cppc_read_file(cpu, acpi_cppc_value_files[which],
+				  linebuf, sizeof(linebuf));
+	if (len == 0)
+		return 0;
+
+	value = strtoull(linebuf, &endp, 0);
+
+	if (endp == linebuf || errno == ERANGE)
+		return 0;
+
+	return value;
+}

tools/power/cpupower/lib/acpi_cppc.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ACPI_CPPC_H__
+#define __ACPI_CPPC_H__
+
+enum acpi_cppc_value {
+	HIGHEST_PERF,
+	LOWEST_PERF,
+	NOMINAL_PERF,
+	LOWEST_NONLINEAR_PERF,
+	LOWEST_FREQ,
+	NOMINAL_FREQ,
+	REFERENCE_PERF,
+	WRAPAROUND_TIME,
+	MAX_CPPC_VALUE_FILES
+};
+
+unsigned long acpi_cppc_get_data(unsigned int cpu,
+				 enum acpi_cppc_value which);
+
+#endif /* _ACPI_CPPC_H */