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From b1311b8bcd1c096c40dca757ba09d88320188e01 Mon Sep 17 00:00:00 2001
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From: Dave Stevenson <dave.stevenson@raspberrypi.org>
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Date: Wed, 13 Jun 2018 15:21:10 +0100
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Subject: [PATCH 314/454] net: lan78xx: Disable TCP Segmentation Offload (TSO)
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TSO seems to be having issues when packets are dropped and the
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remote end uses Selective Acknowledge (SACK) to denote that
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data is missing. The missing data is never resent, so the
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connection eventually stalls.
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There is a module parameter of enable_tso added to allow
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further debugging without forcing a rebuild of the kernel.
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https://github.com/raspberrypi/linux/issues/2449
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https://github.com/raspberrypi/linux/issues/2482
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Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
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---
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drivers/net/usb/lan78xx.c | 19 +++++++++++++++++--
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1 file changed, 17 insertions(+), 2 deletions(-)
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--- a/drivers/net/usb/lan78xx.c
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+++ b/drivers/net/usb/lan78xx.c
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@@ -415,6 +415,15 @@ static int msg_level = -1;
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module_param(msg_level, int, 0);
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MODULE_PARM_DESC(msg_level, "Override default message level");
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+/* TSO seems to be having some issue with Selective Acknowledge (SACK) that
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+ * results in lost data never being retransmitted.
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+ * Disable it by default now, but adds a module parameter to enable it for
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+ * debug purposes (the full cause is not currently understood).
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+ */
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+static bool enable_tso;
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+module_param(enable_tso, bool, 0644);
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+MODULE_PARM_DESC(enable_tso, "Enables TCP segmentation offload");
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+
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static int lan78xx_read_reg(struct lan78xx_net *dev, u32 index, u32 *data)
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{
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u32 *buf = kmalloc(sizeof(u32), GFP_KERNEL);
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@@ -2898,8 +2907,14 @@ static int lan78xx_bind(struct lan78xx_n
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if (DEFAULT_RX_CSUM_ENABLE)
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dev->net->features |= NETIF_F_RXCSUM;
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- if (DEFAULT_TSO_CSUM_ENABLE)
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- dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_SG;
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+ if (DEFAULT_TSO_CSUM_ENABLE) {
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+ dev->net->features |= NETIF_F_SG;
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+ /* Use module parameter to control TCP segmentation offload as
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+ * it appears to cause issues.
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+ */
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+ if (enable_tso)
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+ dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6;
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+ }
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if (DEFAULT_VLAN_RX_OFFLOAD)
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dev->net->features |= NETIF_F_HW_VLAN_CTAG_RX;
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