Index: usr.sbin/powerd/powerd.c
===================================================================
--- usr.sbin/powerd/powerd.c	(revision 265255)
+++ usr.sbin/powerd/powerd.c	(working copy)
@@ -175,7 +175,62 @@
 	return (0);
 }
 
+/*
+ * Fetch minimum and maximum available frequencies.
+ *
+ * The fetch can start at any given minimum/maximum values with which
+ * to cap the search for.  For example, if minfreq is set at 500, then
+ * no frequencies below 500 will be considered.
+ *
+ * A value of -1 for each parameter as "no default" - ie, find the
+ * largest and/or smallest available.
+ */
 static int
+fetch_min_max_freqs(int *minfreq, int *maxfreq)
+{
+	char *freqstr = NULL, *p, *q;
+	int i, j;
+	size_t len = 0;
+	int freq, pwr;
+	int ret;
+	int numfreqs = 0;
+
+	if (sysctl(levels_mib, 4, NULL, &len, NULL, 0))
+		return (-1);
+	if ((freqstr = malloc(len)) == NULL)
+		return (-1);
+	if (sysctl(levels_mib, 4, freqstr, &len, NULL, 0))
+		return (-1);
+
+	/* XXX why not strsep? */
+	for (p = freqstr; *p != '\0'; p++)
+		if (*p == ' ')
+			numfreqs++;
+
+	for (i = 0, j = 0, p = freqstr; i < numfreqs; i++) {
+		q = strchr(p, ' ');
+		if (q != NULL)
+			*q = '\0';
+		if (sscanf(p, "%d/%d", &freq, &pwr) != 2) {
+			ret = -1;
+			goto finish;
+		}
+
+		if (*minfreq == -1 || freq < *minfreq)
+			*minfreq = freq;
+		if (*maxfreq == -1 || freq > *maxfreq)
+			*maxfreq = freq;
+
+		p = q + 1;
+	}
+
+finish:
+	free(freqstr);
+	return (0);
+
+}
+
+static int
 read_freqs(int *numfreqs, int **freqs, int **power, int minfreq, int maxfreq)
 {
 	char *freqstr, *p, *q;
@@ -450,6 +505,7 @@
 	const char *pidfile = NULL;
 	int freq, curfreq, initfreq, *freqs, i, j, *mwatts, numfreqs, load;
 	int minfreq = -1, maxfreq = -1;
+	int minfreq_avail, maxfreq_avail;
 	int ch, mode, mode_ac, mode_battery, mode_none, idle, to;
 	uint64_t mjoules_used;
 	size_t len;
@@ -543,6 +599,20 @@
 	if (sysctlnametomib("dev.cpu.0.freq_levels", levels_mib, &len))
 		err(1, "lookup freq_levels");
 
+	/* Fetch the minimum/maximum frequency range supported */
+	minfreq_avail = -1;
+	maxfreq_avail = -1;
+	if (fetch_min_max_freqs(&minfreq_avail, &maxfreq_avail) != 0)
+		err(1, "error reading supported CPU frequencies");
+
+	/*
+	 * If no minimum frequency is given, cap it at 50% of the
+	 * frequency.  Some boards go all the way down to 100MHz
+	 * which is extremely slow to .. well, do anything from.
+	 */
+	if (minfreq == -1)
+		minfreq = maxfreq_avail / 2;
+
 	/* Check if we can read the load and supported freqs. */
 	if (read_usage_times(NULL))
 		err(1, "read_usage_times");