Index: dev/sdhci/sdhci.c
===================================================================
--- dev/sdhci/sdhci.c	(revision 246891)
+++ dev/sdhci/sdhci.c	(working copy)
@@ -69,6 +69,9 @@
 TUNABLE_INT("hw.sdhci.debug", &sdhci_debug);
 SYSCTL_INT(_hw_sdhci, OID_AUTO, debug, CTLFLAG_RW, &sdhci_debug, 0, "Debug level");
 
+int	sdhci_max_freq = 25000000;
+TUNABLE_INT("hw.sdhci.max_freq", &sdhci_max_freq);
+
 #define RD1(slot, off)	SDHCI_READ_1((slot)->bus, (slot), (off))
 #define RD2(slot, off)	SDHCI_READ_2((slot)->bus, (slot), (off))
 #define RD4(slot, off)	SDHCI_READ_4((slot)->bus, (slot), (off))
@@ -231,8 +234,16 @@
 
 	if (clock == slot->clock)
 		return;
-	slot->clock = clock;
 
+	if (clock <= sdhci_max_freq)
+	    slot->clock = clock;
+	else {
+	    device_printf(slot->dev, "%d is more then max_freq, using %d\n", clock,
+			    sdhci_max_freq);
+	    slot->clock = sdhci_max_freq;
+	    clock = sdhci_max_freq;
+	}
+
 	/* Turn off the clock. */
 	WR2(slot, SDHCI_CLOCK_CONTROL, 0);
 	/* If no clock requested - left it so. */