From a179aad12badc43201cbf45d1e8ed2c1383c76b9 Mon Sep 17 00:00:00 2001
From: Mattias Barthel <mattias.barthel@atlascopco.com>
Date: Tue, 29 Apr 2025 11:08:26 +0200
Subject: [PATCH] net: fec: ERR007885 Workaround for conventional TX
Activate TX hang workaround also in
fec_enet_txq_submit_skb() when TSO is not enabled.
Errata: ERR007885
Symptoms: NETDEV WATCHDOG: eth0 (fec): transmit queue 0 timed out
commit 37d6017b84f7 ("net: fec: Workaround for imx6sx enet tx hang when enable three queues")
There is a TDAR race condition for mutliQ when the software sets TDAR
and the UDMA clears TDAR simultaneously or in a small window (2-4 cycles).
This will cause the udma_tx and udma_tx_arbiter state machines to hang.
So, the Workaround is checking TDAR status four time, if TDAR cleared by
hardware and then write TDAR, otherwise don't set TDAR.
Fixes: 53bb20d1faba ("net: fec: add variable reg_desc_active to speed things up")
Signed-off-by: Mattias Barthel <mattias.barthel@atlascopco.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250429090826.3101258-1-mattiasbarthel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
drivers/net/ethernet/freescale/fec_main.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index a86cfebedaa8..17e9bddb9ddd 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -714,7 +714,12 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
txq->bd.cur = bdp;
/* Trigger transmission start */
- writel(0, txq->bd.reg_desc_active);
+ if (!(fep->quirks & FEC_QUIRK_ERR007885) ||
+ !readl(txq->bd.reg_desc_active) ||
+ !readl(txq->bd.reg_desc_active) ||
+ !readl(txq->bd.reg_desc_active) ||
+ !readl(txq->bd.reg_desc_active))
+ writel(0, txq->bd.reg_desc_active);
return 0;
}