net: stmmac: dwmac4: 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 with GMAC5 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/dwmac4_lib.c

@@ -124,9 +124,9 @@ void dwmac4_disable_dma_irq(void __iomem *ioaddr, u32 chan)
 int dwmac4_dma_interrupt(void __iomem *ioaddr,
 			 struct stmmac_extra_stats *x, u32 chan)
 {
-	int ret = 0;
-
 	u32 intr_status = readl(ioaddr + DMA_CHAN_STATUS(chan));
+	u32 intr_en = readl(ioaddr + DMA_CHAN_INTR_ENA(chan));
+	int ret = 0;
 
 	/* ABNORMAL interrupts */
 	if (unlikely(intr_status & DMA_CHAN_STATUS_AIS)) {
@@ -151,29 +151,19 @@ int dwmac4_dma_interrupt(void __iomem *ioaddr,
 	if (likely(intr_status & DMA_CHAN_STATUS_NIS)) {
 		x->normal_irq_n++;
 		if (likely(intr_status & DMA_CHAN_STATUS_RI)) {
-			u32 value;
-
-			value = readl(ioaddr + DMA_CHAN_INTR_ENA(chan));
-			/* to schedule NAPI on real RIE event. */
-			if (likely(value & DMA_CHAN_INTR_ENA_RIE)) {
-				x->rx_normal_irq_n++;
-				ret |= handle_rx;
-			}
+			x->rx_normal_irq_n++;
+			ret |= handle_rx;
 		}
-		if (likely(intr_status & DMA_CHAN_STATUS_TI)) {
+		if (likely(intr_status & (DMA_CHAN_STATUS_TI |
+					  DMA_CHAN_STATUS_TBU))) {
 			x->tx_normal_irq_n++;
 			ret |= handle_tx;
 		}
 		if (unlikely(intr_status & DMA_CHAN_STATUS_ERI))
 			x->rx_early_irq++;
 	}
 
-	/* Clear the interrupt by writing a logic 1 to the chanX interrupt
-	 * status [21-0] expect reserved bits [5-3]
-	 */
-	writel((intr_status & 0x3fffc7),
-	       ioaddr + DMA_CHAN_STATUS(chan));
-
+	writel(intr_status & intr_en, ioaddr + DMA_CHAN_STATUS(chan));
 	return ret;
 }