1 files changed, 88 insertions, 0 deletions
diff --git a/tools/power/cpupower/utils/helpers/msr.c b/tools/power/cpupower/utils/helpers/msr.c
new file mode 100644
index 000000000..8b0b6be74
--- /dev/null
+++ b/tools/power/cpupower/utils/helpers/msr.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+#if defined(__i386__) || defined(__x86_64__)
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#include "helpers/helpers.h"
+
+/* Intel specific MSRs */
+#define MSR_IA32_PERF_STATUS		0x198
+#define MSR_IA32_MISC_ENABLES		0x1a0
+#define MSR_NEHALEM_TURBO_RATIO_LIMIT	0x1ad
+
+/*
+ * read_msr
+ *
+ * Will return 0 on success and -1 on failure.
+ * Possible errno values could be:
+ * EFAULT -If the read/write did not fully complete
+ * EIO    -If the CPU does not support MSRs
+ * ENXIO  -If the CPU does not exist
+ */
+
+int read_msr(int cpu, unsigned int idx, unsigned long long *val)
+{
+	int fd;
+	char msr_file_name[64];
+
+	sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
+	fd = open(msr_file_name, O_RDONLY);
+	if (fd < 0)
+		return -1;
+	if (lseek(fd, idx, SEEK_CUR) == -1)
+		goto err;
+	if (read(fd, val, sizeof *val) != sizeof *val)
+		goto err;
+	close(fd);
+	return 0;
+ err:
+	close(fd);
+	return -1;
+}
+
+/*
+ * write_msr
+ *
+ * Will return 0 on success and -1 on failure.
+ * Possible errno values could be:
+ * EFAULT -If the read/write did not fully complete
+ * EIO    -If the CPU does not support MSRs
+ * ENXIO  -If the CPU does not exist
+ */
+int write_msr(int cpu, unsigned int idx, unsigned long long val)
+{
+	int fd;
+	char msr_file_name[64];
+
+	sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
+	fd = open(msr_file_name, O_WRONLY);
+	if (fd < 0)
+		return -1;
+	if (lseek(fd, idx, SEEK_CUR) == -1)
+		goto err;
+	if (write(fd, &val, sizeof val) != sizeof val)
+		goto err;
+	close(fd);
+	return 0;
+ err:
+	close(fd);
+	return -1;
+}
+
+unsigned long long msr_intel_get_turbo_ratio(unsigned int cpu)
+{
+	unsigned long long val;
+	int ret;
+
+	if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_HAS_TURBO_RATIO))
+		return -1;
+
+	ret = read_msr(cpu, MSR_NEHALEM_TURBO_RATIO_LIMIT, &val);
+	if (ret)
+		return ret;
+	return val;
+}
+#endif