net: sparx5: Add spinlock for frame transmission from CPU

Both registers used when doing manual injection or fdma injection are
shared between all the net devices of the switch. It was noticed that
when having two process which each of them trying to inject frames on
different ethernet ports, that the HW started to behave strange, by
sending out more frames then expected. When doing fdma injection it is
required to set the frame in the DCB and then make sure that the next
pointer of the last DCB is invalid. But because there is no locks for
this, then easily this pointer between the DCB can be broken and then it
would create a loop of DCBs. And that means that the HW will
continuously transmit these frames in a loop. Until the SW will break
this loop.
Therefore to fix this issue, add a spin lock for when accessing the
registers for manual or fdma injection.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Fixes: f3cad2611a77 ("net: sparx5: add hostmode with phylink support")
Link: https://lore.kernel.org/r/20240219080043.1561014-1-horatiu.vultur@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 4 insertions, 0 deletions

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
index d1f7fc8b1b71ab..3c066b62e68947 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
@@ -757,6 +757,7 @@ static int mchp_sparx5_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, sparx5);
 	sparx5->pdev = pdev;
 	sparx5->dev = &pdev->dev;
+	spin_lock_init(&sparx5->tx_lock);
 
 	/* Do switch core reset if available */
 	reset = devm_reset_control_get_optional_shared(&pdev->dev, "switch");
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
index 6f565c0c0c3dcd..316fed5f273552 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
@@ -280,6 +280,7 @@ struct sparx5 {
 	int xtr_irq;
 	/* Frame DMA */
 	int fdma_irq;
+	spinlock_t tx_lock; /* lock for frame transmission */
 	struct sparx5_rx rx;
 	struct sparx5_tx tx;
 	/* PTP */
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
index 6db6ac6a3bbc26..ac7e1cffbcecf0 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
@@ -244,10 +244,12 @@ netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	skb_tx_timestamp(skb);
+	spin_lock(&sparx5->tx_lock);
 	if (sparx5->fdma_irq > 0)
 		ret = sparx5_fdma_xmit(sparx5, ifh, skb);
 	else
 		ret = sparx5_inject(sparx5, ifh, skb, dev);
+	spin_unlock(&sparx5->tx_lock);
 
 	if (ret == -EBUSY)
 		goto busy;