[net-next,v3] net: ethernet: ti: am65-cpsw: VLAN-aware CPSW only if !DSA

Commit Message

A. Sverdlin Jan. 10, 2025, 12:57 p.m. UTC

From: Alexander Sverdlin <[e-mail]>

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/[e-mail]/
Link: https://lore.kernel.org/linux-arm-kernel/4699400.vD3TdgH1nR@localhost/
Co-developed-by: Siddharth Vadapalli <[e-mail]>
Signed-off-by: Siddharth Vadapalli <[e-mail]>
Signed-off-by: Alexander Sverdlin <[e-mail]>
---
v3: Moved the AM65_CPSW_CTL_VLAN_AWARE deassertion into
    am65_cpsw_nuss_ndo_slave_open()
v2: Thanks to Siddharth it does look much clearer now (conditionally clear
    AM65_CPSW_CTL_VLAN_AWARE instead of setting)

 drivers/net/ethernet/ti/am65-cpsw-nuss.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
index 5465bf872734..9e52928ebfd4 100644
--- 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);