stmmac: Add defines and documentation for enabling flow control

Add defines and documentation for enabling flow control on the stmmac. Flow
control was not implemented correctly on the stmmac driver and is currently
non-functional as a result. This is the first in a series of small patches
to correctly implement this feature.

Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac1000.h

@@ -172,6 +172,7 @@ enum inter_frame_gap {
 /* GMAC FLOW CTRL defines */
 #define GMAC_FLOW_CTRL_PT_MASK	0xffff0000	/* Pause Time Mask */
 #define GMAC_FLOW_CTRL_PT_SHIFT	16
+#define GMAC_FLOW_CTRL_UP	0x00000008	/* Unicast pause frame enable */
 #define GMAC_FLOW_CTRL_RFE	0x00000004	/* Rx Flow Control Enable */
 #define GMAC_FLOW_CTRL_TFE	0x00000002	/* Tx Flow Control Enable */
 #define GMAC_FLOW_CTRL_FCB_BPA	0x00000001	/* Flow Control Busy ... */
@@ -246,6 +247,56 @@ enum ttc_control {
 #define DMA_CONTROL_FEF		0x00000080
 #define DMA_CONTROL_FUF		0x00000040
 
+/* Receive flow control activation field
+ * RFA field in DMA control register, bits 23,10:9
+ */
+#define DMA_CONTROL_RFA_MASK	0x00800600
+
+/* Receive flow control deactivation field
+ * RFD field in DMA control register, bits 22,12:11
+ */
+#define DMA_CONTROL_RFD_MASK	0x00401800
+
+/* RFD and RFA fields are encoded as follows
+ *
+ *   Bit Field
+ *   0,00 - Full minus 1KB (only valid when rxfifo >= 4KB and EFC enabled)
+ *   0,01 - Full minus 2KB (only valid when rxfifo >= 4KB and EFC enabled)
+ *   0,10 - Full minus 3KB (only valid when rxfifo >= 4KB and EFC enabled)
+ *   0,11 - Full minus 4KB (only valid when rxfifo > 4KB and EFC enabled)
+ *   1,00 - Full minus 5KB (only valid when rxfifo > 8KB and EFC enabled)
+ *   1,01 - Full minus 6KB (only valid when rxfifo > 8KB and EFC enabled)
+ *   1,10 - Full minus 7KB (only valid when rxfifo > 8KB and EFC enabled)
+ *   1,11 - Reserved
+ *
+ * RFD should always be > RFA for a given FIFO size. RFD == RFA may work,
+ * but packet throughput performance may not be as expected.
+ *
+ * Be sure that bit 3 in GMAC Register 6 is set for Unicast Pause frame
+ * detection (IEEE Specification Requirement, Annex 31B, 31B.1, Pause
+ * Description).
+ *
+ * Be sure that DZPA (bit 7 in Flow Control Register, GMAC Register 6),
+ * is set to 0. This allows pause frames with a quanta of 0 to be sent
+ * as an XOFF message to the link peer.
+ */
+
+#define RFA_FULL_MINUS_1K	0x00000000
+#define RFA_FULL_MINUS_2K	0x00000200
+#define RFA_FULL_MINUS_3K	0x00000400
+#define RFA_FULL_MINUS_4K	0x00000600
+#define RFA_FULL_MINUS_5K	0x00800000
+#define RFA_FULL_MINUS_6K	0x00800200
+#define RFA_FULL_MINUS_7K	0x00800400
+
+#define RFD_FULL_MINUS_1K	0x00000000
+#define RFD_FULL_MINUS_2K	0x00000800
+#define RFD_FULL_MINUS_3K	0x00001000
+#define RFD_FULL_MINUS_4K	0x00001800
+#define RFD_FULL_MINUS_5K	0x00400000
+#define RFD_FULL_MINUS_6K	0x00400800
+#define RFD_FULL_MINUS_7K	0x00401000
+
 enum rtc_control {
 	DMA_CONTROL_RTC_64 = 0x00000000,
 	DMA_CONTROL_RTC_32 = 0x00000008,