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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Bryan Whitehead <Bryan.Whitehead@microchip.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.20 34/76] lan743x: Fix TX Stall Issue
Date:   Fri,  8 Mar 2019 13:49:46 +0100
Message-Id: <20190308124916.027484092@linuxfoundation.org>
In-Reply-To: <20190308124914.789210760@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bryan Whitehead <Bryan.Whitehead@microchip.com>

[ Upstream commit 90490ef7269906423a1c1b917fc24be8b1602658 ]

It has been observed that tx queue stalls while downloading
from certain web sites (example www.speedtest.net)

The cause has been tracked down to a corner case where
dma descriptors where not setup properly. And there for a tx
completion interrupt was not signaled.

This fix corrects the problem by properly marking the end of
a multi descriptor transmission.

Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
Signed-off-by: Bryan Whitehead <Bryan.Whitehead@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/microchip/lan743x_main.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -1400,7 +1400,8 @@ static int lan743x_tx_frame_start(struct
 }
 
 static void lan743x_tx_frame_add_lso(struct lan743x_tx *tx,
-				     unsigned int frame_length)
+				     unsigned int frame_length,
+				     int nr_frags)
 {
 	/* called only from within lan743x_tx_xmit_frame.
 	 * assuming tx->ring_lock has already been acquired.
@@ -1410,6 +1411,10 @@ static void lan743x_tx_frame_add_lso(str
 
 	/* wrap up previous descriptor */
 	tx->frame_data0 |= TX_DESC_DATA0_EXT_;
+	if (nr_frags <= 0) {
+		tx->frame_data0 |= TX_DESC_DATA0_LS_;
+		tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+	}
 	tx_descriptor = &tx->ring_cpu_ptr[tx->frame_tail];
 	tx_descriptor->data0 = tx->frame_data0;
 
@@ -1514,8 +1519,11 @@ static void lan743x_tx_frame_end(struct
 	u32 tx_tail_flags = 0;
 
 	/* wrap up previous descriptor */
-	tx->frame_data0 |= TX_DESC_DATA0_LS_;
-	tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+	if ((tx->frame_data0 & TX_DESC_DATA0_DTYPE_MASK_) ==
+	    TX_DESC_DATA0_DTYPE_DATA_) {
+		tx->frame_data0 |= TX_DESC_DATA0_LS_;
+		tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+	}
 
 	tx_descriptor = &tx->ring_cpu_ptr[tx->frame_tail];
 	buffer_info = &tx->buffer_info[tx->frame_tail];
@@ -1600,7 +1608,7 @@ static netdev_tx_t lan743x_tx_xmit_frame
 	}
 
 	if (gso)
-		lan743x_tx_frame_add_lso(tx, frame_length);
+		lan743x_tx_frame_add_lso(tx, frame_length, nr_frags);
 
 	if (nr_frags <= 0)
 		goto finish;