2019-09-19 14:43:19 +00:00
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From 103afc4641ab8d6587e981a5e3fda27427a8bf4b Mon Sep 17 00:00:00 2001
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2019-08-09 17:50:30 +00:00
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From: Phil Elwell <phil@raspberrypi.org>
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Date: Fri, 9 Aug 2019 08:51:43 +0100
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2019-12-23 12:42:55 +00:00
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Subject: [PATCH] net: bcmgenet: Workaround #2 for Pi4 Ethernet fail
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2019-08-09 17:50:30 +00:00
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Some combinations of Pi 4Bs and Ethernet switches don't reliably get a
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DCHP-assigned IP address, leaving the unit with a self=assigned 169.254
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address. In the failure case, the Pi is left able to receive packets
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but not send them, suggesting that the MAC<->PHY link is getting into
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a bad state.
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It has been found empirically that skipping a reset step by the genet
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driver prevents the failures. No downsides have been discovered yet,
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and unlike the forced renegotiation it doesn't increase the time to
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get an IP address, so the workaround is enabled by default; add
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genet.skip_umac_reset=n
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to the command line to disable it.
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See: https://github.com/raspberrypi/linux/issues/3108
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Signed-off-by: Phil Elwell <phil@raspberrypi.org>
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---
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drivers/net/ethernet/broadcom/genet/bcmgenet.c | 9 +++++++++
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1 file changed, 9 insertions(+)
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--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
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+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
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@@ -72,6 +72,10 @@
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#define GENET_RDMA_REG_OFF (priv->hw_params->rdma_offset + \
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TOTAL_DESC * DMA_DESC_SIZE)
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+static bool skip_umac_reset = true;
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+module_param(skip_umac_reset, bool, 0444);
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+MODULE_PARM_DESC(skip_umac_reset, "Skip UMAC reset step");
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+
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static inline void bcmgenet_writel(u32 value, void __iomem *offset)
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{
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/* MIPS chips strapped for BE will automagically configure the
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@@ -1993,6 +1997,11 @@ static void reset_umac(struct bcmgenet_p
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bcmgenet_rbuf_ctrl_set(priv, 0);
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udelay(10);
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+ if (skip_umac_reset) {
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+ pr_warn("Skipping UMAC reset\n");
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+ return;
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+ }
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+
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/* disable MAC while updating its registers */
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bcmgenet_umac_writel(priv, 0, UMAC_CMD);
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