net: fec: ERR007885 Workaround for XDP TX path

The ERR007885 will lead to a TDAR race condition for mutliQ when the
driver sets TDAR and the UDMA clears TDAR simultaneously or in a small
window (2-4 cycles). And it will cause the udma_tx and udma_tx_arbiter
state machines to hang. Therefore, the commit 53bb20d1faba ("net: fec:
add variable reg_desc_active to speed things up") and the commit
a179aad12bad ("net: fec: ERR007885 Workaround for conventional TX") have
added the workaround to fix the potential issue for the conventional TX
path. Similarly, the XDP TX path should also have the potential hang
issue, so add the workaround for XDP TX path.

Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Link: https://patch.msgid.link/20251128025915.2486943-1-wei.fang@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index c685a5c0cc51a586566b52b1ea8559bd50b8399f..a753265961af511b2131806f2c7e5c8413459eae 100644 (file)
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3933,7 +3933,12 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
        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;
 }