netdev - [PATCH 12/12] net: ll_temac: Enable DMA when ready, not before

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Date:   Fri, 26 Apr 2019 09:32:31 +0200
From:   Esben Haabendal <esben@...nix.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Michal Simek <michal.simek@...inx.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Yang Wei <yang.wei9@....com.cn>,
        YueHaibing <yuehaibing@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 12/12] net: ll_temac: Enable DMA when ready, not before

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@...nix.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 a30ac11..b8e3dbd 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -316,17 +316,21 @@ static int temac_dma_bd_init(struct net_device *ndev)
 		    CHNL_CTRL_IRQ_EN | CHNL_CTRL_IRQ_ERR_EN |
 		    CHNL_CTRL_IRQ_DLY_EN | CHNL_CTRL_IRQ_COAL_EN);
 
-	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:
@@ -790,6 +794,7 @@ 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;
-- 
2.4.11