net: ethernet: mediatek: Enable GDM GDMA_DROP_ALL mode

Enable GDM GDMA_DROP_ALL mode to drop all packet during the
stop operation. This is recommended by the mt762x HW design
to drop all packet from GMAC before stopping PDMA.
Signed-off-by: MarkLee <Mark-MC.Lee@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -2279,6 +2279,8 @@ static int mtk_stop(struct net_device *dev)
 	if (!refcount_dec_and_test(&eth->dma_refcnt))
 		return 0;
 
+	mtk_gdm_config(eth, MTK_GDMA_DROP_ALL);
+
 	mtk_tx_irq_disable(eth, MTK_TX_DONE_INT);
 	mtk_rx_irq_disable(eth, MTK_RX_DONE_INT);
 	napi_disable(&eth->tx_napi);

drivers/net/ethernet/mediatek/mtk_eth_soc.h

@@ -85,6 +85,7 @@
 #define MTK_GDMA_TCS_EN		BIT(21)
 #define MTK_GDMA_UCS_EN		BIT(20)
 #define MTK_GDMA_TO_PDMA	0x0
+#define MTK_GDMA_DROP_ALL       0x7777
 
 /* Unicast Filter MAC Address Register - Low */
 #define MTK_GDMA_MAC_ADRL(x)	(0x508 + (x * 0x1000))