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net: fec: ERR007885 Workaround for conventional TX

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[ Upstream commit a179aad12badc43201cbf45d1e8ed2c1383c76b9 ]

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 37d6017b84 ("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: 53bb20d1fa ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Mattias Barthel
2025-04-29 11:08:26 +02:00
committed by Greg Kroah-Hartman
parent dae1ce27ce
commit 0e32cbcbc4
1 changed files with 6 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/net/ethernet/freescale/fec_main.c
View File

@@ -695,7 +695,12 @@ 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;
}