stmmac: add DMA support for GMAC 4.xx

DMA behavior is linked to descriptor management:

-descriptor mechanism (Tx for example, but it is exactly the same for RX):
-useful registers:
-DMA_CH#_TxDesc_Ring_Len: length of transmit descriptor ring
-DMA_CH#_TxDesc_List_Address: start address of the ring
	-DMA_CH#_TxDesc_Tail_Pointer: address of the last
					      descriptor to send + 1.
	-DMA_CH#_TxDesc_Current_App_TxDesc: address of the current
						    descriptor

-The descriptor Tail Pointer register contains the pointer to the
 descriptor address (N). The base address and the current
 descriptor decide the address of the current descriptor that the
 DMA can process. The descriptors up to one location less than the
 one indicated by the descriptor tail pointer (N-1) are owned by
 the DMA. The DMA continues to process the descriptors until the
 following condition occurs:
 "current descriptor pointer == Descriptor Tail pointer"

Then the DMA goes into suspend mode. The application must perform
a write to descriptor tail pointer register and update the tail
pointer to have the following condition and to start a new transfer:
"current descriptor pointer < Descriptor tail pointer"

The DMA automatically wraps around the base address when the end
of ring is reached.

Up to 8 DMA could be use but currently we only use one (channel0)

Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/Makefile

@@ -3,7 +3,7 @@ stmmac-objs:= stmmac_main.o stmmac_ethtool.o stmmac_mdio.o ring_mode.o	\
 	      chain_mode.o dwmac_lib.o dwmac1000_core.o dwmac1000_dma.o	\
 	      dwmac100_core.o dwmac100_dma.o enh_desc.o norm_desc.o	\
 	      mmc_core.o stmmac_hwtstamp.o stmmac_ptp.o dwmac4_descs.o	\
-	      $(stmmac-y)
+	      dwmac4_dma.o dwmac4_lib.o $(stmmac-y)
 
 # Ordering matters. Generic driver must be last.
 obj-$(CONFIG_STMMAC_PLATFORM)	+= stmmac-platform.o

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

@@ -41,6 +41,8 @@
 /* Synopsys Core versions */
 #define	DWMAC_CORE_3_40	0x34
 #define	DWMAC_CORE_3_50	0x35
+#define	DWMAC_CORE_4_00	0x40
+#define STMMAC_CHAN0	0	/* Always supported and default for all chips */
 
 #define DMA_TX_SIZE 512
 #define DMA_RX_SIZE 512
@@ -270,6 +272,7 @@ enum dma_irq_status {
 #define	CORE_PCS_ANE_COMPLETE		(1 << 5)
 #define	CORE_PCS_LINK_STATUS		(1 << 6)
 #define	CORE_RGMII_IRQ			(1 << 7)
+#define CORE_IRQ_MTL_RX_OVERFLOW	BIT(8)
 
 /* Physical Coding Sublayer */
 struct rgmii_adv {
@@ -301,8 +304,10 @@ struct dma_features {
 	/* 802.3az - Energy-Efficient Ethernet (EEE) */
 	unsigned int eee;
 	unsigned int av;
+	unsigned int tsoen;
 	/* TX and RX csum */
 	unsigned int tx_coe;
+	unsigned int rx_coe;
 	unsigned int rx_coe_type1;
 	unsigned int rx_coe_type2;
 	unsigned int rxfifo_over_2048;
@@ -425,6 +430,11 @@ struct stmmac_dma_ops {
 			       struct dma_features *dma_cap);
 	/* Program the HW RX Watchdog */
 	void (*rx_watchdog) (void __iomem *ioaddr, u32 riwt);
+	void (*set_tx_ring_len)(void __iomem *ioaddr, u32 len);
+	void (*set_rx_ring_len)(void __iomem *ioaddr, u32 len);
+	void (*set_rx_tail_ptr)(void __iomem *ioaddr, u32 tail_ptr, u32 chan);
+	void (*set_tx_tail_ptr)(void __iomem *ioaddr, u32 tail_ptr, u32 chan);
+	void (*enable_tso)(void __iomem *ioaddr, bool en, u32 chan);
 };
 
 struct mac_device_info;
@@ -473,6 +483,7 @@ struct stmmac_hwtimestamp {
 };
 
 extern const struct stmmac_hwtimestamp stmmac_ptp;
+extern const struct stmmac_mode_ops dwmac4_ring_mode_ops;
 
 struct mac_link {
 	int port;