amd-xgbe: Add receive buffer unavailable statistic

Add a statistic that tracks how many times an interrupt is generated for
a receive buffer not being available to the hardware which prevents the
hardware from being able to DMA the received data.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amd/xgbe/xgbe-drv.c

@@ -360,6 +360,9 @@ static irqreturn_t xgbe_isr(int irq, void *data)
 			}
 		}
 
+		if (XGMAC_GET_BITS(dma_ch_isr, DMA_CH_SR, RBU))
+			pdata->ext_stats.rx_buffer_unavailable++;
+
 		/* Restart the device on a Fatal Bus Error */
 		if (XGMAC_GET_BITS(dma_ch_isr, DMA_CH_SR, FBE))
 			schedule_work(&pdata->restart_work);

drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c

@@ -179,6 +179,7 @@ static const struct xgbe_stats xgbe_gstring_stats[] = {
 	XGMAC_MMC_STAT("rx_watchdog_errors", rxwatchdogerror),
 	XGMAC_MMC_STAT("rx_pause_frames", rxpauseframes),
 	XGMAC_EXT_STAT("rx_split_header_packets", rx_split_header_packets),
+	XGMAC_EXT_STAT("rx_buffer_unavailable", rx_buffer_unavailable),
 };
 
 #define XGBE_STATS_COUNT	ARRAY_SIZE(xgbe_gstring_stats)

drivers/net/ethernet/amd/xgbe/xgbe.h

@@ -582,6 +582,7 @@ struct xgbe_mmc_stats {
 struct xgbe_ext_stats {
 	u64 tx_tso_packets;
 	u64 rx_split_header_packets;
+	u64 rx_buffer_unavailable;
 };
 
 struct xgbe_hw_if {