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tools/power x86_energy_perf_policy: Add Android MSR device support

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Add support for Android MSR device paths which use /dev/msrN format
instead of the standard Linux /dev/cpu/N/msr format. The tool now
probes both path formats at startup and uses the appropriate one.

This enables x86_energy_perf_policy to work on Android systems where
MSR devices follow a different naming convention while maintaining
full compatibility with standard Linux systems.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Kaushlendra Kumar
2025-10-03 16:33:19 +05:30
committed by Len Brown
parent d71cb404f0
commit 2ff4b59f2e
1 changed files with 46 additions and 8 deletions
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54
tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
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@@ -95,6 +95,9 @@ unsigned int bdx_highest_ratio;
#define PATH_TO_CPU "/sys/devices/system/cpu/"
#define SYSFS_PATH_MAX 255
/* keep Default as a linux path */
static int use_android_msr_path;
/*
* maintain compatibility with original implementation, but don't document it:
*/
@@ -678,16 +681,41 @@ void err_on_hypervisor(void)
"not supported on this virtual machine");
}
static void probe_msr_path_format(void)
{
struct stat sb;
char test_path[32];
/* Test standard Linux path */
sprintf(test_path, "/dev/cpu/%d/msr", base_cpu);
if (stat(test_path, &sb) == 0) {
use_android_msr_path = 0;
return;
}
/* Test Android-style path */
sprintf(test_path, "/dev/msr%d", base_cpu);
if (stat(test_path, &sb) == 0) {
use_android_msr_path = 1;
return;
}
/* If neither exists, keep the default Linux format */
use_android_msr_path = 0;
}
int get_msr(int cpu, int offset, unsigned long long *msr)
{
int retval;
char pathname[32];
int fd;
sprintf(pathname, "/dev/cpu/%d/msr", cpu);
sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", cpu);
fd = open(pathname, O_RDONLY);
if (fd < 0)
err(-1, "%s open failed, try chown or chmod +r /dev/cpu/*/msr, or run as root", pathname);
err(-1, "%s open failed, try chown or chmod +r %s, or run as root",
pathname, use_android_msr_path ? "/dev/msr*" : "/dev/cpu/*/msr");
retval = pread(fd, msr, sizeof(*msr), offset);
if (retval != sizeof(*msr)) {
@@ -708,10 +736,11 @@ int put_msr(int cpu, int offset, unsigned long long new_msr)
int retval;
int fd;
sprintf(pathname, "/dev/cpu/%d/msr", cpu);
sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", cpu);
fd = open(pathname, O_RDWR);
if (fd < 0)
err(-1, "%s open failed, try chown or chmod +r /dev/cpu/*/msr, or run as root", pathname);
err(-1, "%s open failed, try chown or chmod +r %s, or run as root",
pathname, use_android_msr_path ? "/dev/msr*" : "/dev/cpu/*/msr");
retval = pwrite(fd, &new_msr, sizeof(new_msr), offset);
if (retval != sizeof(new_msr))
@@ -1427,10 +1456,15 @@ void probe_dev_msr(void)
struct stat sb;
char pathname[32];
sprintf(pathname, "/dev/cpu/%d/msr", base_cpu);
if (stat(pathname, &sb))
if (system("/sbin/modprobe msr > /dev/null 2>&1"))
err(-5, "no /dev/cpu/0/msr, Try \"# modprobe msr\" ");
sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", base_cpu);
if (stat(pathname, &sb)) {
if (system("/sbin/modprobe msr > /dev/null 2>&1")) {
if (use_android_msr_path)
err(-5, "no /dev/msr0, Try \"# modprobe msr\" ");
else
err(-5, "no /dev/cpu/0/msr, Try \"# modprobe msr\" ");
}
}
}
static void get_cpuid_or_exit(unsigned int leaf,
@@ -1547,6 +1581,10 @@ void parse_cpuid(void)
int main(int argc, char **argv)
{
set_base_cpu();
/* probe MSR path */
probe_msr_path_format();
probe_dev_msr();
init_data_structures();