ixgbe: update {P}FC thresholds to account for X540 and loopback

Revise high and low threshold marks wrt flow control to account
for the X540 devices and latency introduced by the loopback
switch.

Without this it was in theory possible to drop frames on a
supposedly lossless link with X540 or SR-IOV enabled.

Previously we used a magic number in a define to calculate the
threshold values. This made it difficult to sort out exactly
which latencies were or were not being accounted for. Here
I was overly explicit and tried to used #define names that would
be recognizable after reading the IEEE 802.1Qbb specification.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 55 insertions, 7 deletions

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h b/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
index 9a03341e5261..16dd461d4af3 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
@@ -404,6 +404,7 @@
 #define IXGBE_WUPL_LENGTH_MASK 0xFFFF
 
 /* DCB registers */
+#define MAX_TRAFFIC_CLASS        8
 #define IXGBE_RMCS      0x03D00
 #define IXGBE_DPMCS     0x07F40
 #define IXGBE_PDPMCS    0x0CD00
@@ -2323,13 +2324,60 @@ typedef u32 ixgbe_physical_layer;
 #define IXGBE_PHYSICAL_LAYER_10GBASE_XAUI 0x1000
 #define IXGBE_PHYSICAL_LAYER_SFP_ACTIVE_DA 0x2000
 
-/* Flow Control Macros */
-#define PAUSE_RTT	8
-#define PAUSE_MTU(MTU)	((MTU + 1024 - 1) / 1024)
+/* Flow Control Data Sheet defined values
+ * Calculation and defines taken from 802.1bb Annex O
+ */
+
+/* BitTimes (BT) conversion */
+#define IXGBE_BT2KB(BT) ((BT + 1023) / (8 * 1024))
+#define IXGBE_B2BT(BT) (BT * 8)
+
+/* Calculate Delay to respond to PFC */
+#define IXGBE_PFC_D	672
+
+/* Calculate Cable Delay */
+#define IXGBE_CABLE_DC	5556 /* Delay Copper */
+#define IXGBE_CABLE_DO	5000 /* Delay Optical */
+
+/* Calculate Interface Delay X540 */
+#define IXGBE_PHY_DC	25600	/* Delay 10G BASET */
+#define IXGBE_MAC_DC	8192	/* Delay Copper XAUI interface */
+#define IXGBE_XAUI_DC	(2 * 2048) /* Delay Copper Phy */
+
+#define IXGBE_ID_X540	(IXGBE_MAC_DC + IXGBE_XAUI_DC + IXGBE_PHY_DC)
+
+/* Calculate Interface Delay 82598, 82599 */
+#define IXGBE_PHY_D	12800
+#define IXGBE_MAC_D	4096
+#define IXGBE_XAUI_D	(2 * 1024)
+
+#define IXGBE_ID	(IXGBE_MAC_D + IXGBE_XAUI_D + IXGBE_PHY_D)
+
+/* Calculate Delay incurred from higher layer */
+#define IXGBE_HD	6144
+
+/* Calculate PCI Bus delay for low thresholds */
+#define IXGBE_PCI_DELAY	10000
+
+/* Calculate X540 delay value in bit times */
+#define IXGBE_FILL_RATE (36 / 25)
+
+#define IXGBE_DV_X540(LINK, TC) (IXGBE_FILL_RATE * \
+				 (IXGBE_B2BT(LINK) + IXGBE_PFC_D + \
+				 (2 * IXGBE_CABLE_DC) + \
+				 (2 * IXGBE_ID_X540) + \
+				 IXGBE_HD + IXGBE_B2BT(TC)))
+
+/* Calculate 82599, 82598 delay value in bit times */
+#define IXGBE_DV(LINK, TC) (IXGBE_FILL_RATE * \
+			    (IXGBE_B2BT(LINK) + IXGBE_PFC_D + \
+			    (2 * IXGBE_CABLE_DC) + (2 * IXGBE_ID) + \
+			    IXGBE_HD + IXGBE_B2BT(TC)))
 
-#define FC_HIGH_WATER(MTU) ((((PAUSE_RTT + PAUSE_MTU(MTU)) * 144) + 99) / 100 +\
-				PAUSE_MTU(MTU))
-#define FC_LOW_WATER(MTU)  (2 * (2 * PAUSE_MTU(MTU) + PAUSE_RTT))
+/* Calculate low threshold delay values */
+#define IXGBE_LOW_DV_X540(TC) (2 * IXGBE_B2BT(TC) + \
+			       (IXGBE_FILL_RATE * IXGBE_PCI_DELAY))
+#define IXGBE_LOW_DV(TC)      (2 * IXGBE_LOW_DV_X540(TC))
 
 /* Software ATR hash keys */
 #define IXGBE_ATR_BUCKET_HASH_KEY    0x3DAD14E2
@@ -2548,7 +2596,7 @@ struct ixgbe_bus_info {
 
 /* Flow control parameters */
 struct ixgbe_fc_info {
-	u32 high_water; /* Flow Control High-water */
+	u32 high_water[MAX_TRAFFIC_CLASS]; /* Flow Control High-water */
 	u32 low_water; /* Flow Control Low-water */
 	u16 pause_time; /* Flow Control Pause timer */
 	bool send_xon; /* Flow control send XON */