net: ethernet: ti: am65-cpsw: VLAN-aware CPSW only if !DSA

Only configure VLAN-aware CPSW mode if no port is used as DSA CPU port.
VLAN-aware mode interferes with some DSA tagging schemes and makes stacking
DSA switches downstream of CPSW impossible. Previous attempts to address
the issue linked below.

Link: https://lore.kernel.org/netdev/20240227082815.2073826-1-s-vadapalli@ti.com/
Link: https://lore.kernel.org/linux-arm-kernel/4699400.vD3TdgH1nR@localhost/
Co-developed-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://patch.msgid.link/20250110125737.546184-1-alexander.sverdlin@siemens.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
index dcb6662b473d73c0d27e966a72bc21dc9d879f88..0fb5f92f28f6753d2eea3854aa6d855c66c6c39f 100644 (file)
--- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
+++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
@@ -32,6 +32,7 @@
 #include <linux/dma/ti-cppi5.h>
 #include <linux/dma/k3-udma-glue.h>
 #include <net/page_pool/helpers.h>
+#include <net/dsa.h>
 #include <net/switchdev.h>
 
 #include "cpsw_ale.h"
@@ -1014,6 +1015,15 @@ static int am65_cpsw_nuss_ndo_slave_open(struct net_device *ndev)
 
        common->usage_count++;
 
+       /* VLAN aware CPSW mode is incompatible with some DSA tagging schemes.
+        * Therefore disable VLAN_AWARE mode if any of the ports is a DSA Port.
+        */
+       if (netdev_uses_dsa(ndev)) {
+               reg = readl(common->cpsw_base + AM65_CPSW_REG_CTL);
+               reg &= ~AM65_CPSW_CTL_VLAN_AWARE;
+               writel(reg, common->cpsw_base + AM65_CPSW_REG_CTL);
+       }
+
        am65_cpsw_port_set_sl_mac(port, ndev->dev_addr);
        am65_cpsw_port_enable_dscp_map(port);