hwpstate: use CPU_FOREACH when binding to all available processors

Also, add a comment mentioning _PSD - on some systems it's enough to
put one logical CPU into a particular P-state to make other CPUs in
the same domain to enter that P-state.

Also, call sched_unbind() after the loop - sched_bind() automatically
rebinds from previous CPU to a new one, and the new arrangement of code
is safer against early loop exit.

Plus one minor style nit.

MFC after:	10 days

1 files changed, 8 insertions, 12 deletions

diff --git a/sys/x86/cpufreq/hwpstate.c b/sys/x86/cpufreq/hwpstate.c
index 18659d7c1e3c..272792658e62 100644
--- a/sys/x86/cpufreq/hwpstate.c
+++ b/sys/x86/cpufreq/hwpstate.c
@@ -157,7 +157,6 @@ DRIVER_MODULE(hwpstate, cpu, hwpstate_driver, hwpstate_devclass, 0, 0);
 static int
 hwpstate_goto_pstate(device_t dev, int pstate)
 {
-	struct pcpu *pc;
 	int i;
 	uint64_t msr;
 	int j;
@@ -171,18 +170,15 @@ hwpstate_goto_pstate(device_t dev, int pstate)
 	if(limit > id)
 		id = limit;
 
-	error = 0;
 	/*
 	 * We are going to the same Px-state on all cpus.
+	 * Probably should take _PSD into account.
 	 */
-	for (i = 0; i < mp_ncpus; i++) {
-		/* Find each cpu. */
-		pc = pcpu_find(i);
-		if (pc == NULL)
-			return (ENXIO);
-		thread_lock(curthread);
+	error = 0;
+	CPU_FOREACH(i) {
 		/* Bind to each cpu. */
-		sched_bind(curthread, pc->pc_cpuid);
+		thread_lock(curthread);
+		sched_bind(curthread, i);
 		thread_unlock(curthread);
 		HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n",
 			id, PCPU_GET(cpuid));
@@ -204,10 +200,10 @@ hwpstate_goto_pstate(device_t dev, int pstate)
 			HWPSTATE_DEBUG(dev, "error: loop is not enough.\n");
 			error = ENXIO;
 		}
-		thread_lock(curthread);
-		sched_unbind(curthread);
-		thread_unlock(curthread);
 	}
+	thread_lock(curthread);
+	sched_unbind(curthread);
+	thread_unlock(curthread);
 	return (error);
 }