r8169: fix rtl8125b PAUSE frames blasting when suspended

When FIFO reaches near full state, device will issue pause frame.
If pause slot is enabled(set to 1), in this time, device will issue
pause frame only once. But if pause slot is disabled(set to 0), device
will keep sending pause frames until FIFO reaches near empty state.

When pause slot is disabled, if there is no one to handle receive
packets, device FIFO will reach near full state and keep sending
pause frames. That will impact entire local area network.

This issue can be reproduced in Chromebox (not Chromebook) in
developer mode running a test image (and v5.10 kernel):
1) ping -f $CHROMEBOX (from workstation on same local network)
2) run "powerd_dbus_suspend" from command line on the $CHROMEBOX
3) ping $ROUTER (wait until ping fails from workstation)

Takes about ~20-30 seconds after step 2 for the local network to
stop working.

Fix this issue by enabling pause slot to only send pause frame once
when FIFO reaches near full state.

Fixes: f1bce4a ("r8169: add support for RTL8125")
Reported-by: Grant Grundler <[email protected]>
Tested-by: Grant Grundler <[email protected]>
Cc: [email protected]
Signed-off-by: ChunHao Lin <[email protected]>
Reviewed-by: Jacob Keller <[email protected]>
Reviewed-by: Heiner Kallweit <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: ChunHao Lin

drivers/net/ethernet/realtek/r8169_main.c

@@ -196,6 +196,7 @@ enum rtl_registers {
 					/* No threshold before first PCI xfer */
 #define	RX_FIFO_THRESH			(7 << RXCFG_FIFO_SHIFT)
 #define	RX_EARLY_OFF			(1 << 11)
+#define	RX_PAUSE_SLOT_ON		(1 << 11)	/* 8125b and later */
 #define	RXCFG_DMA_SHIFT			8
 					/* Unlimited maximum PCI burst. */
 #define	RX_DMA_BURST			(7 << RXCFG_DMA_SHIFT)
@@ -2306,9 +2307,13 @@ static void rtl_init_rxcfg(struct rtl8169_private *tp)
 	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_53:
 		RTL_W32(tp, RxConfig, RX128_INT_EN | RX_MULTI_EN | RX_DMA_BURST | RX_EARLY_OFF);
 		break;
-	case RTL_GIGA_MAC_VER_61 ... RTL_GIGA_MAC_VER_63:
+	case RTL_GIGA_MAC_VER_61:
 		RTL_W32(tp, RxConfig, RX_FETCH_DFLT_8125 | RX_DMA_BURST);
 		break;
+	case RTL_GIGA_MAC_VER_63:
+		RTL_W32(tp, RxConfig, RX_FETCH_DFLT_8125 | RX_DMA_BURST |
+			RX_PAUSE_SLOT_ON);
+		break;
 	default:
 		RTL_W32(tp, RxConfig, RX128_INT_EN | RX_DMA_BURST);
 		break;