[PATCH net] net: lan969x: don't disable hardirqs in fdma tx clear

[Daniel Machon]

lan969x_fdma_tx_clear_buf() runs from the NAPI poll and frees the skbs
of completed tx DCBs with napi_consume_skb(), under sparx5->tx_lock.

Before this patch, the lock is taken with spin_lock_irqsave(), so the
skbs are freed with hardirqs disabled. RX skbs are marked for page_pool
recycling, so when such an skb is forwarded back out and its tx
completion frees it here, the free path reaches __page_pool_put_page(),
which warns via lockdep_assert_no_hardirq().

Take tx_lock with a plain spin_lock(), as the only other tx_lock user,
sparx5_port_xmit_impl(), already does. tx_clear_buf() is only called
from softirq context, so disabling hardirqs is not needed.

Found with lockdep enabled (CONFIG_PROVE_LOCKING), which the assert
depends on. Reproduced on lan969x by redirecting received frames out of
another port with tc mirred.

Fixes: d84ad2c0d80c ("net: lan969x: add FDMA implementation")
Signed-off-by: Daniel Machon <daniel.machon at microchip.com>
---
 drivers/net/ethernet/microchip/sparx5/lan969x/lan969x_fdma.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/lan969x/lan969x_fdma.c b/drivers/net/ethernet/microchip/sparx5/lan969x/lan969x_fdma.c
index c7e0e58ff0f7..053d125eda65 100644
--- a/drivers/net/ethernet/microchip/sparx5/lan969x/lan969x_fdma.c
+++ b/drivers/net/ethernet/microchip/sparx5/lan969x/lan969x_fdma.c
@@ -54,10 +54,9 @@ static void lan969x_fdma_tx_clear_buf(struct sparx5 *sparx5, int weight)
 {
 	struct fdma *fdma = &sparx5->tx.fdma;
 	struct sparx5_tx_buf *db;
-	unsigned long flags;
 	int i;
 
-	spin_lock_irqsave(&sparx5->tx_lock, flags);
+	spin_lock(&sparx5->tx_lock);
 
 	for (i = 0; i < fdma->n_dcbs; ++i) {
 		db = &sparx5->tx.dbs[i];
@@ -83,7 +82,7 @@ static void lan969x_fdma_tx_clear_buf(struct sparx5 *sparx5, int weight)
 		db->used = false;
 	}
 
-	spin_unlock_irqrestore(&sparx5->tx_lock, flags);
+	spin_unlock(&sparx5->tx_lock);
 }
 
 static void lan969x_fdma_free_pages(struct sparx5_rx *rx)

---
base-commit: 07bd391eb9572e74f073c49acef327611234f9bb
change-id: 20261019-lan969x-fdma-tx-clear-irq-d86877f96431

Best regards,
-- 
Daniel Machon <daniel.machon at microchip.com>