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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 06/52] lan743x: Fix TX Stall Issue
Date:   Mon, 18 Mar 2019 10:24:53 +0100
Message-Id: <20190318083844.162308248@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 deb6bfabdbb634e91f36a4e9cb00a7137d72d886 ]

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

The cause has been tracked down to a corner case where
the tx interrupt vector was disabled automatically, but
was not re enabled later.

The lan743x has two mechanisms to enable/disable individual
interrupts. Interrupts can be enabled/disabled by individual
source, and they can also be enabled/disabled by individual
vector which has been mapped to the source. Both must be
enabled for interrupts to work properly.

The TX code path, primarily uses the interrupt enable/disable of
the TX source bit, while leaving the vector enabled all the time.

However, while investigating this issue it was noticed that
the driver requested the use of the vector auto clear feature.

The test above revealed a case where the vector enable was
cleared unintentionally.

This patch fixes the issue by deleting the lines that request
the vector auto clear feature to be used.

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 |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -585,8 +585,7 @@ static int lan743x_intr_open(struct lan7
 
 		if (adapter->csr.flags &
 		   LAN743X_CSR_FLAG_SUPPORTS_INTR_AUTO_SET_CLR) {
-			flags = LAN743X_VECTOR_FLAG_VECTOR_ENABLE_AUTO_CLEAR |
-				LAN743X_VECTOR_FLAG_VECTOR_ENABLE_AUTO_SET |
+			flags = LAN743X_VECTOR_FLAG_VECTOR_ENABLE_AUTO_SET |
 				LAN743X_VECTOR_FLAG_SOURCE_ENABLE_AUTO_SET |
 				LAN743X_VECTOR_FLAG_SOURCE_ENABLE_AUTO_CLEAR |
 				LAN743X_VECTOR_FLAG_SOURCE_STATUS_AUTO_CLEAR;
@@ -599,12 +598,6 @@ static int lan743x_intr_open(struct lan7
 			/* map TX interrupt to vector */
 			int_vec_map1 |= INT_VEC_MAP1_TX_VEC_(index, vector);
 			lan743x_csr_write(adapter, INT_VEC_MAP1, int_vec_map1);
-			if (flags &
-			    LAN743X_VECTOR_FLAG_VECTOR_ENABLE_AUTO_CLEAR) {
-				int_vec_en_auto_clr |= INT_VEC_EN_(vector);
-				lan743x_csr_write(adapter, INT_VEC_EN_AUTO_CLR,
-						  int_vec_en_auto_clr);
-			}
 
 			/* Remove TX interrupt from shared mask */
 			intr->vector_list[0].int_mask &= ~int_bit;