[PATCH v2 2/4] net: dsa: Extend ksz9477 TAG setup to support HSR frames duplication

[Lukasz Majewski <lukma@denx.de>]

The KSZ9477 has support for HSR (High-Availability Seamless Redundancy).
One of its offloading (i.e. performed in the switch IC hardware) features
is to duplicate received frame to both HSR aware switch ports.

To achieve this goal - the tail TAG needs to be modified. To be more
specific, both ports must be marked as destination (egress) ones.

Moreover, according to AN3474 application note, the lookup bit (10)
should not be set in the tail tag.

Last but not least - the NETIF_F_HW_HSR_DUP flag indicates that the device
supports HSR and assures (in HSR core code) that frame is sent only once
from HOST to switch with tail tag indicating both ports.

Information about bits to be set in tag is provided via KSZ generic
ksz_hsr_get_ports() function.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
- Use ksz_hsr_get_ports() to obtain the bits values corresponding to
  HSR aware ports
---
 drivers/net/dsa/microchip/ksz_common.c | 12 ++++++++++++
 include/linux/dsa/ksz_common.h         |  1 +
 net/dsa/tag_ksz.c                      |  5 +++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index d9d843efd111..579fde54d1e1 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -3421,6 +3421,18 @@ static int ksz_setup_tc(struct dsa_switch *ds, int port,
 	}
 }
 
+u16 ksz_hsr_get_ports(struct dsa_switch *ds)
+{
+	struct ksz_device *dev = ds->priv;
+
+	switch (dev->chip_id) {
+	case KSZ9477_CHIP_ID:
+		return dev->hsr_ports;
+	}
+
+	return 0;
+}
+
 static const struct dsa_switch_ops ksz_switch_ops = {
 	.get_tag_protocol	= ksz_get_tag_protocol,
 	.connect_tag_protocol   = ksz_connect_tag_protocol,
diff --git a/include/linux/dsa/ksz_common.h b/include/linux/dsa/ksz_common.h
index 576a99ca698d..fa3d9b0f3a72 100644
--- a/include/linux/dsa/ksz_common.h
+++ b/include/linux/dsa/ksz_common.h
@@ -50,4 +50,5 @@ ksz_tagger_data(struct dsa_switch *ds)
 	return ds->tagger_data;
 }
 
+u16 ksz_hsr_get_ports(struct dsa_switch *ds);
 #endif /* _NET_DSA_KSZ_COMMON_H_ */
diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index ea100bd25939..903db95c37ee 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -293,6 +293,11 @@ static struct sk_buff *ksz9477_xmit(struct sk_buff *skb,
 	if (is_link_local_ether_addr(hdr->h_dest))
 		val |= KSZ9477_TAIL_TAG_OVERRIDE;
 
+	if (dev->features & NETIF_F_HW_HSR_DUP) {
+		val &= ~KSZ9477_TAIL_TAG_LOOKUP;
+		val |= ksz_hsr_get_ports(dp->ds);
+	}
+
 	*tag = cpu_to_be16(val);
 
 	return ksz_defer_xmit(dp, skb);
-- 
2.20.1