From 83510e3cc63b58e4f3831b5b001a3722af405903 Mon Sep 17 00:00:00 2001
From: Esben Haabendal <esben@geanix.com>
Date: Tue, 30 Apr 2019 09:17:59 +0200
Subject: [PATCH 1/4] net: ll_temac: Enable DMA when ready, not before
Git-commit: 73f7375d3ed6ad372f1e9404007a0c866063d773
Patch-mainline: v5.2-rc1
References: git-fixes

As soon as TAILDESCR_PTR is written, DMA transfers might start.
Let's ensure we are ready to receive DMA IRQ's before doing that.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
 drivers/net/ethernet/xilinx/ll_temac_main.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index 357e7c104409..10a28cea72be 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -295,17 +295,21 @@ static int temac_dma_bd_init(struct net_device *ndev)
 					  CHNL_CTRL_IRQ_IOE);
 	/* 0xff010283 */
 
-	lp->dma_out(lp, RX_CURDESC_PTR,  lp->rx_bd_p);
-	lp->dma_out(lp, RX_TAILDESC_PTR,
-		       lp->rx_bd_p + (sizeof(*lp->rx_bd_v) * (RX_BD_NUM - 1)));
-	lp->dma_out(lp, TX_CURDESC_PTR, lp->tx_bd_p);
-
 	/* Init descriptor indexes */
 	lp->tx_bd_ci = 0;
 	lp->tx_bd_next = 0;
 	lp->tx_bd_tail = 0;
 	lp->rx_bd_ci = 0;
 
+	/* Enable RX DMA transfers */
+	wmb();
+	lp->dma_out(lp, RX_CURDESC_PTR,  lp->rx_bd_p);
+	lp->dma_out(lp, RX_TAILDESC_PTR,
+		       lp->rx_bd_p + (sizeof(*lp->rx_bd_v) * (RX_BD_NUM - 1)));
+
+	/* Prepare for TX DMA transfer */
+	lp->dma_out(lp, TX_CURDESC_PTR, lp->tx_bd_p);
+
 	return 0;
 
 out:
@@ -802,6 +806,7 @@ static int temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	skb_tx_timestamp(skb);
 
 	/* Kick off the transfer */
+	wmb();
 	lp->dma_out(lp, TX_TAILDESC_PTR, tail_p); /* DMA start */
 
 	return NETDEV_TX_OK;
-- 
2.16.4