net: dsa: b53: prevent BRCM_HDR access on older devices

Older switches don't implement BRCM_HDR register so we should avoid
reading or writing it.

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Link: https://patch.msgid.link/20250614080000.1884236-11-noltari@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index daf7c1906711441105b646c9cac14f0f5f3c4a27..2bcbb003b1fd6389840cd1fd338fbec9e7f654f5 100644 (file)
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -730,6 +730,11 @@ void b53_brcm_hdr_setup(struct dsa_switch *ds, int port)
                hdr_ctl |= GC_FRM_MGMT_PORT_M;
        b53_write8(dev, B53_MGMT_PAGE, B53_GLOBAL_CONFIG, hdr_ctl);
 
+       /* B53_BRCM_HDR not present on devices with legacy tags */
+       if (dev->tag_protocol == DSA_TAG_PROTO_BRCM_LEGACY ||
+           dev->tag_protocol == DSA_TAG_PROTO_BRCM_LEGACY_FCS)
+               return;
+
        /* Enable Broadcom tags for IMP port */
        b53_read8(dev, B53_MGMT_PAGE, B53_BRCM_HDR, &hdr_ctl);
        if (tag_en)