[TG3]: Prescaler fix

Internal hardware timers become inaccurate after link events.  Clock
frequency switches performed by the CPMU fail to adjust timer
prescalers.  The fix is to detect core clock frequency changes during
link events and adjust the timer prescalers accordingly.
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -3154,6 +3154,22 @@ static int tg3_setup_phy(struct tg3 *tp, int force_reset)
 		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,

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