tools/power x86_energy_perf_policy: Enhance HWP enable

On enabling HWP, preserve the reserved bits in MSR_PM_ENABLE.

Also, skip writing the MSR_PM_ENABLE if HWP is already enabled.

Signed-off-by: Len Brown <len.brown@intel.com>

Author: lenb

tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c

@@ -1166,13 +1166,18 @@ int update_hwp_request_pkg(int pkg)
 
 int enable_hwp_on_cpu(int cpu)
 {
-	unsigned long long msr;
+	unsigned long long old_msr, new_msr;
+
+	get_msr(cpu, MSR_PM_ENABLE, &old_msr);
+
+	if (old_msr & 1)
+		return 0;	/* already enabled */
 
-	get_msr(cpu, MSR_PM_ENABLE, &msr);
-	put_msr(cpu, MSR_PM_ENABLE, 1);
+	new_msr = old_msr | 1;
+	put_msr(cpu, MSR_PM_ENABLE, new_msr);
 
 	if (verbose)
-		printf("cpu%d: MSR_PM_ENABLE old: %d new: %d\n", cpu, (unsigned int) msr, 1);
+		printf("cpu%d: MSR_PM_ENABLE old: %llX new: %llX\n", cpu, old_msr, new_msr);
 
 	return 0;
 }