diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index bb3b734..ecd64a22 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -3154,6 +3154,22 @@
 		err = tg3_setup_copper_phy(tp, force_reset);
 	}
 
+	if (tp->pci_chip_rev_id == CHIPREV_ID_5784_A0) {
+		u32 val, scale;
+
+		val = tr32(TG3_CPMU_CLCK_STAT) & CPMU_CLCK_STAT_MAC_CLCK_MASK;
+		if (val == CPMU_CLCK_STAT_MAC_CLCK_62_5)
+			scale = 65;
+		else if (val == CPMU_CLCK_STAT_MAC_CLCK_6_25)
+			scale = 6;
+		else
+			scale = 12;
+
+		val = tr32(GRC_MISC_CFG) & ~GRC_MISC_CFG_PRESCALAR_MASK;
+		val |= (scale << GRC_MISC_CFG_PRESCALAR_SHIFT);
+		tw32(GRC_MISC_CFG, val);
+	}
+
 	if (tp->link_config.active_speed == SPEED_1000 &&
 	    tp->link_config.active_duplex == DUPLEX_HALF)
 		tw32(MAC_TX_LENGTHS,
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 5b799ff..d325ab5 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -874,7 +874,14 @@
 #define TG3_CPMU_HST_ACC		0x0000361c
 #define  CPMU_HST_ACC_MACCLK_MASK	 0x001f0000
 #define  CPMU_HST_ACC_MACCLK_6_25	 0x00130000
-/* 0x3620 --> 0x365c unused */
+/* 0x3620 --> 0x3630 unused */
+
+#define TG3_CPMU_CLCK_STAT		0x00003630
+#define  CPMU_CLCK_STAT_MAC_CLCK_MASK	 0x001f0000
+#define  CPMU_CLCK_STAT_MAC_CLCK_62_5	 0x00000000
+#define  CPMU_CLCK_STAT_MAC_CLCK_12_5	 0x00110000
+#define  CPMU_CLCK_STAT_MAC_CLCK_6_25	 0x00130000
+/* 0x3634 --> 0x365c unused */
 
 #define TG3_CPMU_MUTEX_REQ		0x0000365c
 #define  CPMU_MUTEX_REQ_DRIVER		 0x00001000