Implement priorities. This allows a driver (say, for cooling purposes) to

override the current freq level temporarily and restore it when the
higher priority condition is past.  Note that only the first overridden
value is saved.  Callers pass NULL to CPUFREQ_SET to restore the saved
level.  Priorities are not yet used so this commit should have no effect.

1 files changed, 38 insertions, 4 deletions

diff --git a/sys/kern/kern_cpu.c b/sys/kern/kern_cpu.c
index ff1d006..85b33d1 100644
--- a/sys/kern/kern_cpu.c
+++ b/sys/kern/kern_cpu.c
@@ -57,9 +57,11 @@ __FBSDID("$FreeBSD$");
 
 struct cpufreq_softc {
 	struct cf_level			curr_level;
-	int				priority;
-	int				all_count;
+	int				curr_priority;
+	struct cf_level			saved_level;
+	int				saved_priority;
 	struct cf_level_lst		all_levels;
+	int				all_count;
 	device_t			dev;
 	struct sysctl_ctx_list		sysctl_ctx;
 };
@@ -120,6 +122,7 @@ cpufreq_attach(device_t dev)
 	sysctl_ctx_init(&sc->sysctl_ctx);
 	TAILQ_INIT(&sc->all_levels);
 	sc->curr_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
+	sc->saved_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
 
 	/*
 	 * Only initialize one set of sysctls for all CPUs.  In the future,
@@ -185,6 +188,21 @@ cf_set_method(device_t dev, const struct cf_level *level, int priority)
 	if (strcmp(timecounter->tc_name, "TSC") == 0)
 		return (EBUSY);
 
+	/*
+	 * If the caller didn't specify a level and one is saved, prepare to
+	 * restore the saved level.  If none has been saved, return an error.
+	 * If they did specify one, but the requested level has a lower
+	 * priority, don't allow the new level right now.
+	 */
+	if (level == NULL) {
+		if (sc->saved_level.total_set.freq != CPUFREQ_VAL_UNKNOWN) {
+			level = &sc->saved_level;
+			priority = sc->saved_priority;
+		} else
+			return (ENXIO);
+	} else if (priority < sc->curr_priority)
+		return (EPERM);
+
 	/* If already at this level, just return. */
 	if (CPUFREQ_CMP(sc->curr_level.total_set.freq, level->total_set.freq))
 		return (0);
@@ -226,9 +244,25 @@ cf_set_method(device_t dev, const struct cf_level *level, int priority)
 		}
 	}
 
-	/* Record the current level. */
+	/* If we were restoring a saved state, reset it to "unused". */
+	if (level == &sc->saved_level) {
+		sc->saved_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
+		sc->saved_priority = 0;
+	}
+
+	/*
+	 * Before recording the current level, check if we're going to a
+	 * higher priority and have not saved a level yet.  If so, save the
+	 * previous level and priority.
+	 */
+	if (sc->curr_level.total_set.freq != CPUFREQ_VAL_UNKNOWN &&
+	    sc->saved_level.total_set.freq == CPUFREQ_VAL_UNKNOWN &&
+	    priority > sc->curr_priority) {
+		sc->saved_level = sc->curr_level;
+		sc->saved_priority = sc->curr_priority;
+	}
 	sc->curr_level = *level;
-	sc->priority = priority;
+	sc->curr_priority = priority;
 	error = 0;
 
 out: