net: stmmac: dwxgmac2: Also use TBU interrupt to clean TX path

TBU interrupt is a normal interrupt and can be used to trigger the
cleaning of TX path. Lets check if it's active in DMA interrupt handler.

While at it, refactor a little bit the function:
	- Don't check if RI is enabled because at function exit we will
	  only clear the interrupts that are enabled so, no event will
	  be missed.

In my tests withe XGMAC2 this increased performance.
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h

@@ -193,9 +193,10 @@
 #define XGMAC_AIE			BIT(14)
 #define XGMAC_RBUE			BIT(7)
 #define XGMAC_RIE			BIT(6)
+#define XGMAC_TBUE			BIT(2)
 #define XGMAC_TIE			BIT(0)
 #define XGMAC_DMA_INT_DEFAULT_EN	(XGMAC_NIE | XGMAC_AIE | XGMAC_RBUE | \
-					XGMAC_RIE | XGMAC_TIE)
+					XGMAC_RIE | XGMAC_TBUE | XGMAC_TIE)
 #define XGMAC_DMA_CH_Rx_WATCHDOG(x)	(0x0000313c + (0x80 * (x)))
 #define XGMAC_RWT			GENMASK(7, 0)
 #define XGMAC_DMA_CH_STATUS(x)		(0x00003160 + (0x80 * (x)))
@@ -204,6 +205,7 @@
 #define XGMAC_FBE			BIT(12)
 #define XGMAC_RBU			BIT(7)
 #define XGMAC_RI			BIT(6)
+#define XGMAC_TBU			BIT(2)
 #define XGMAC_TPS			BIT(1)
 #define XGMAC_TI			BIT(0)
 

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c

@@ -283,12 +283,10 @@ static int dwxgmac2_dma_interrupt(void __iomem *ioaddr,
 		x->normal_irq_n++;
 
 		if (likely(intr_status & XGMAC_RI)) {
-			if (likely(intr_en & XGMAC_RIE)) {
-				x->rx_normal_irq_n++;
-				ret |= handle_rx;
-			}
+			x->rx_normal_irq_n++;
+			ret |= handle_rx;
 		}
-		if (likely(intr_status & XGMAC_TI)) {
+		if (likely(intr_status & (XGMAC_TI | XGMAC_TBU))) {
 			x->tx_normal_irq_n++;
 			ret |= handle_tx;
 		}