Latest kernel allows to disable C-states via:
/sys/devices/system/cpu/cpuX/cpuidle/stateY/disable
This patch provides lower level sysfs access functions to make use of this
interface.
A later patch will implement the higher level stuff.
Signed-off-by: Thomas Renninger <trenn@xxxxxxx>
---
tools/power/cpupower/utils/helpers/sysfs.c | 116 +++++++++++++++++++++++++++-
tools/power/cpupower/utils/helpers/sysfs.h | 8 ++
2 files changed, 123 insertions(+), 1 deletions(-)
diff --git a/tools/power/cpupower/utils/helpers/sysfs.c b/tools/power/cpupower/utils/helpers/sysfs.c
index 891f671..5cdc600 100644
--- a/tools/power/cpupower/utils/helpers/sysfs.c
+++ b/tools/power/cpupower/utils/helpers/sysfs.c
@@ -89,6 +89,33 @@ int sysfs_is_cpu_online(unsigned int cpu)
/* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */
+
+/* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */
+
+/*
+ * helper function to check whether a file under "../cpuX/cpuidle/stateX/" dir
+ * exists.
+ * For example the functionality to disable c-states was introduced in later
+ * kernel versions, this function can be used to explicitly check for this
+ * feature.
+ *
+ * returns 1 if the file exists, 0 otherwise.
+ */
+unsigned int sysfs_idlestate_file_exists(unsigned int cpu,
+ unsigned int idlestate,
+ const char *fname)
+{
+ char path[SYSFS_PATH_MAX];
+ struct stat statbuf;
+
+
+ snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
+ cpu, idlestate, fname);
+ if (stat(path, &statbuf) != 0)
+ return 0;
+ return 1;
+}
+
/*
* helper function to read file from /sys into given buffer
* fname is a relative path under "cpuX/cpuidle/stateX/" dir
@@ -121,6 +148,40 @@ unsigned int sysfs_idlestate_read_file(unsigned int cpu, unsigned int idlestate,
return (unsigned int) numread;
}
+/*
+ * helper function to write a new value to a /sys file
+ * fname is a relative path under "../cpuX/cpuidle/cstateY/" dir
+ *
+ * Returns the number of bytes written or 0 on error
+ */
+static
+unsigned int sysfs_idlestate_write_file(unsigned int cpu,
+ unsigned int idlestate,
+ const char *fname,
+ const char *value, size_t len)
+{
+ char path[SYSFS_PATH_MAX];
+ int fd;
+ ssize_t numwrite;
+
+ snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
+ cpu, idlestate, fname);
+
+ fd = open(path, O_WRONLY);
+ if (fd == -1)
+ return 0;
+
+ numwrite = write(fd, value, len);
+ if (numwrite < 1) {
+ close(fd);
+ return 0;
+ }
+
+ close(fd);
+
+ return (unsigned int) numwrite;
+}
+
/* read access to files which contain one numeric value */
enum idlestate_value {
@@ -128,6 +189,7 @@ enum idlestate_value {
IDLESTATE_POWER,
IDLESTATE_LATENCY,
IDLESTATE_TIME,
+ IDLESTATE_DISABLE,
MAX_IDLESTATE_VALUE_FILES
};
@@ -136,6 +198,7 @@ static const char *idlestate_value_files[MAX_IDLESTATE_VALUE_FILES] = {
[IDLESTATE_POWER] = "power",
[IDLESTATE_LATENCY] = "latency",
[IDLESTATE_TIME] = "time",
+ [IDLESTATE_DISABLE] = "disable",
};
static unsigned long long sysfs_idlestate_get_one_value(unsigned int cpu,
@@ -205,8 +268,59 @@ static char *sysfs_idlestate_get_one_string(unsigned int cpu,
return result;
}
+/*
+ * Returns:
+ * 1 if disabled
+ * 0 if enabled
+ * -1 if idlestate is not available
+ * -2 if disabling is not supported by the kernel
+ */
+int sysfs_is_idlestate_disabled(unsigned int cpu,
+ unsigned int idlestate)
+{
+ if (sysfs_get_idlestate_count(cpu) < idlestate)
+ return -1;
+
+ if (!sysfs_idlestate_file_exists(cpu, idlestate,
+ idlestate_value_files[IDLESTATE_DISABLE]))
+ return -2;
+ return sysfs_idlestate_get_one_value(cpu, idlestate, IDLESTATE_DISABLE);
+}
+
+/*
+ * Pass 1 as last argument to disable or 0 to enable the state
+ * Returns:
+ * 0 on success
+ * negative values on error, for example:
+ * -1 if idlestate is not available
+ * -2 if disabling is not supported by the kernel
+ * -3 No write access to disable/enable C-states
+ */
+int sysfs_idlestate_disable(unsigned int cpu,
+ unsigned int idlestate,
+ unsigned int disable)
+{
+ char value[SYSFS_PATH_MAX];
+ int bytes_written;
+
+ if (sysfs_get_idlestate_count(cpu) < idlestate)
+ return -1;
+
+ if (!sysfs_idlestate_file_exists(cpu, idlestate,
+ idlestate_value_files[IDLESTATE_DISABLE]))
+ return -2;
+
+ snprintf(value, SYSFS_PATH_MAX, "%u", disable);
+
+ bytes_written = sysfs_idlestate_write_file(cpu, idlestate, "disable",
+ value, sizeof(disable));
+ if (bytes_written)
+ return 0;
+ return -3;
+}
+
unsigned long sysfs_get_idlestate_latency(unsigned int cpu,
- unsigned int idlestate)
+ unsigned int idlestate)
{
return sysfs_idlestate_get_one_value(cpu, idlestate, IDLESTATE_LATENCY);
}
diff --git a/tools/power/cpupower/utils/helpers/sysfs.h b/tools/power/cpupower/utils/helpers/sysfs.h
index 0401a97..d28f11f 100644
--- a/tools/power/cpupower/utils/helpers/sysfs.h
+++ b/tools/power/cpupower/utils/helpers/sysfs.h
@@ -7,8 +7,16 @@
extern unsigned int sysfs_read_file(const char *path, char *buf, size_t buflen);
+extern unsigned int sysfs_idlestate_file_exists(unsigned int cpu,
+ unsigned int idlestate,
+ const char *fname);
+
extern int sysfs_is_cpu_online(unsigned int cpu);
+extern int sysfs_is_idlestate_disabled(unsigned int cpu,
+ unsigned int idlestate);
+extern int sysfs_idlestate_disable(unsigned int cpu, unsigned int idlestate,
+ unsigned int disable);
extern unsigned long sysfs_get_idlestate_latency(unsigned int cpu,
unsigned int idlestate);
extern unsigned long sysfs_get_idlestate_usage(unsigned int cpu,
--
1.7.6.1
