[[RFC PATCH v4 net-next] 2/2] net: dsa: hsr: Enable in KSZ9477 switch HW HSR offloading

Lukasz Majewski
2023-09-06T15:28:23Z

This patch adds functions for providing in KSZ9477 switch HSR
(High-availability Seamless Redundancy) hardware offloading.

According to AN3474 application note following features are provided:
- TX packet duplication from host to switch (NETIF_F_HW_HSR_DUP)
- RX packet duplication discarding
- Prevention of packet loop

For last two ones - there is a probability that some packets will not
be filtered in HW (in some special cases - described in AN3474).
Hence, the HSR core code shall be used to discard those not caught frames.

Moreover, some switch registers adjustments are required - like setting
MAC address of HSR network interface.

Additionally, the KSZ9477 switch has been configured to forward frames
between HSR ports (e.g. 1,2) members to provide support for
NETIF_F_HW_HSR_FWD flag.

Join and leave functions are written in a way, that are executed with
single port - i.e. configuration is NOT done only when second HSR port
is configured.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
Changes for v2:
- Use struct ksz_device to store hsr ports information (not struct dsa)

Changes for v3:
- Enable in-switch forwarding of frames between HSR ports (i.e. enable
bridging of those two ports)

- The NETIF_F_HW_HSR_FWD flag has been marked as supported by the HSR
network device

- Remove ETH MAC address validity check as it is done earlier in the net
driver

- Add comment regarding adding support for NETIF_F_HW_HSR_FWD flag

Changes for v4:
- Merge patches for ksz_common.c and ksz9477.c

- Remove code to set global self-address filtering as this bit has
already been set at ksz9477_reset_switch() function. Update also
comment.

- Use already available ksz9477_cfg_port_member() instead of ksz_prmw32()

- Add description about chip limitations

- Allow having only one offloaded hsr interface (e.g. hsr0). Other ones
(like hsr1) will have only SW HSR support

- Add check if MAC address of HSR device is equal to one from DSA master
- Rewrite the code to support per port join (i.e. not making init only
when second HSR port is join)
- Add check to allow only one HSR port HW offloading
- Add hsr_ports to ksz_device struct to allow clean removal of network
interfaces composing hsr device
---
drivers/net/dsa/microchip/ksz9477.c | 81 ++++++++++++++++++++++++++
drivers/net/dsa/microchip/ksz9477.h | 2 +
drivers/net/dsa/microchip/ksz_common.c | 76 ++++++++++++++++++++++++
drivers/net/dsa/microchip/ksz_common.h | 3 +
4 files changed, 162 insertions(+)

diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
index 83b7f2d5c1ea..f36bc427c468 100644
--- a/drivers/net/dsa/microchip/ksz9477.c
+++ b/drivers/net/dsa/microchip/ksz9477.c
@@ -1141,6 +1141,87 @@ int ksz9477_tc_cbs_set_cinc(struct ksz_device *dev, int port, u32 val)
return ksz_pwrite16(dev, port, REG_PORT_MTI_CREDIT_INCREMENT, val);
}

+/* The KSZ9477 provides following HW features to accelerate
+ * HSR frames handling:
+ *
+ * 1. TX PACKET DUPLICATION FROM HOST TO SWITCH
+ * 2. RX PACKET DUPLICATION DISCARDING
+ * 3. PREVENTING PACKET LOOP IN THE RING BY SELF-ADDRESS FILTERING
+ *
+ * Only one from point 1. has the NETIF_F* flag available.
+ *
+ * Ones from point 2 and 3 are "best effort" - i.e. those will
+ * work correctly most of the time, but it may happen that some
+ * frames will not be caught - to be more specific; there is a race
+ * condition in hardware such that, when duplicate packets are received
+ * on member ports very close in time to each other, the hardware fails
+ * to detect that they are duplicates.
+ *
+ * Hence, the SW needs to handle those special cases. However, the speed
+ * up gain is considerable when above features are used.
+ *
+ * Moreover, the NETIF_F_HW_HSR_FWD feature is also enabled, as HSR frames
+ * can be forwarded in the switch fabric between HSR ports.
+ */
+#define KSZ9477_SUPPORTED_HSR_FEATURES (NETIF_F_HW_HSR_DUP | NETIF_F_HW_HSR_FWD)
+
+void ksz9477_hsr_join(struct dsa_switch *ds, int port, struct net_device *hsr)
+{
+ struct ksz_device *dev = ds->priv;
+ struct net_device *slave;
+ u8 i, data;
+
+ /* Program which port(s) shall support HSR */
+ ksz_rmw32(dev, REG_HSR_PORT_MAP__4, BIT(port), BIT(port));
+
+ /* Forward frames between HSR ports (i.e. bridge together HSR ports) */
+ ksz9477_cfg_port_member(dev, port,
+ BIT(dsa_upstream_port(ds, port)) | BIT(port));
+
+ if (!dev->hsr_ports) {
+ /* Enable discarding of received HSR frames */
+ ksz_read8(dev, REG_HSR_ALU_CTRL_0__1, &data);
+ data |= HSR_DUPLICATE_DISCARD;
+ data &= ~HSR_NODE_UNICAST;
+ ksz_write8(dev, REG_HSR_ALU_CTRL_0__1, data);
+
+ /* Self MAC address filtering for HSR frames to avoid
+ * traverse of the HSR ring more than once.
+ *
+ * The HSR port (i.e. hsr0) MAC address is used.
+ */
+ for (i = 0; i < ETH_ALEN; i++)
+ ksz_write8(dev, REG_SW_MAC_ADDR_0 + i,
+ hsr->dev_addr[i]);
+ }
+
+ /* Enable per port self-address filtering.
+ * The global self-address filtering has already been enabled in the
+ * ksz9477_reset_switch() function.
+ */
+ ksz_port_cfg(dev, port, REG_PORT_LUE_CTRL, PORT_SRC_ADDR_FILTER, true);
+
+ /* Setup HW supported features for lan HSR ports */
+ slave = dsa_to_port(ds, port)->slave;
+ slave->features |= KSZ9477_SUPPORTED_HSR_FEATURES;
+
+ pr_debug("%s: HSR join port: %d\n", __func__, port);
+}
+
+void ksz9477_hsr_leave(struct dsa_switch *ds, int port, struct net_device *hsr)
+{
+ struct ksz_device *dev = ds->priv;
+
+ /* Clear port HSR support */
+ ksz_rmw32(dev, REG_HSR_PORT_MAP__4, BIT(port), 0);
+
+ /* Disable forwarding frames between HSR ports */
+ ksz9477_cfg_port_member(dev, port, BIT(dsa_upstream_port(ds, port)));
+
+ /* Disable per port self-address filtering */
+ ksz_port_cfg(dev, port, REG_PORT_LUE_CTRL, PORT_SRC_ADDR_FILTER, false);
+}
+
int ksz9477_switch_init(struct ksz_device *dev)
{
u8 data8;
diff --git a/drivers/net/dsa/microchip/ksz9477.h b/drivers/net/dsa/microchip/ksz9477.h
index a6f425866a29..8625bf474764 100644
--- a/drivers/net/dsa/microchip/ksz9477.h
+++ b/drivers/net/dsa/microchip/ksz9477.h
@@ -56,5 +56,7 @@ int ksz9477_reset_switch(struct ksz_device *dev);
int ksz9477_switch_init(struct ksz_device *dev);
void ksz9477_switch_exit(struct ksz_device *dev);
void ksz9477_port_queue_split(struct ksz_device *dev, int port);
+void ksz9477_hsr_join(struct dsa_switch *ds, int port, struct net_device *hsr);
+void ksz9477_hsr_leave(struct dsa_switch *ds, int port, struct net_device *hsr);

#endif
diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 42db7679c360..b81c3ac422f9 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -16,6 +16,7 @@
#include <linux/etherdevice.h>
#include <linux/if_bridge.h>
#include <linux/if_vlan.h>
+#include <linux/if_hsr.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/of.h>
@@ -3419,6 +3420,79 @@ static int ksz_setup_tc(struct dsa_switch *ds, int port,
}
}

+static int ksz_hsr_join(struct dsa_switch *ds, int port, struct net_device *hsr)
+{
+ struct net_device *dm = dsa_port_to_master(dsa_to_port(ds, port));
+ struct ksz_device *dev = ds->priv;
+ enum hsr_version ver;
+ int ret;
+
+ ret = hsr_get_version(hsr, &ver);
+ if (ret)
+ return ret;
+
+ /* Check if HSR net_device's MAC address equals to DSA master.
+ *
+ * Only in that way one can assure correct operation between
+ * different switch features - like WoL, PAUSE and HSR, which
+ * are using in-switch programmed MAC address.
+ */
+ if (!ether_addr_equal(dm->dev_addr, hsr->dev_addr)) {
+ dev_err(dev->dev,
+ "DSA master and HSR dev MAC must equal for offloading");
+ return -EOPNOTSUPP;
+ }
+
+ switch (dev->chip_id) {
+ case KSZ9477_CHIP_ID:
+ /* KSZ9477 can support HW offloading of only 1 HSR device */
+ if (dev->hsr_dev && hsr != dev->hsr_dev) {
+ dev_err(dev->dev, "Offload supported for a single HSR");
+ return -EOPNOTSUPP;
+ }
+
+ /* KSZ9477 only supports HSR v0 and v1 */
+ if (!(ver == HSR_V0 || ver == HSR_V1)) {
+ dev_err(dev->dev, "Only HSR v0 and v1 supported");
+ return -EOPNOTSUPP;
+ }
+
+ ksz9477_hsr_join(ds, port, hsr);
+ dev->hsr_dev = hsr;
+ dev->hsr_ports |= BIT(port);
+
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ return 0;
+}
+
+static int ksz_hsr_leave(struct dsa_switch *ds, int port,
+ struct net_device *hsr)
+{
+ struct ksz_device *dev = ds->priv;
+ int ret = 0;
+
+ switch (dev->chip_id) {
+ case KSZ9477_CHIP_ID:
+ if (hsr != dev->hsr_dev)
+ return -EOPNOTSUPP;
+
+ ksz9477_hsr_leave(ds, port, hsr);
+ dev->hsr_ports &= ~BIT(port);
+ if (!dev->hsr_ports)
+ dev->hsr_dev = NULL;
+
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ return ret;
+}
+
static const struct dsa_switch_ops ksz_switch_ops = {
.get_tag_protocol = ksz_get_tag_protocol,
.connect_tag_protocol = ksz_connect_tag_protocol,
@@ -3438,6 +3512,8 @@ static const struct dsa_switch_ops ksz_switch_ops = {
.get_sset_count = ksz_sset_count,
.port_bridge_join = ksz_port_bridge_join,
.port_bridge_leave = ksz_port_bridge_leave,
+ .port_hsr_join = ksz_hsr_join,
+ .port_hsr_leave = ksz_hsr_leave,
.port_stp_state_set = ksz_port_stp_state_set,
.port_pre_bridge_flags = ksz_port_pre_bridge_flags,
.port_bridge_flags = ksz_port_bridge_flags,
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index a4de58847dea..e36d459de5a1 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -169,6 +169,9 @@ struct ksz_device {
struct mutex lock_irq; /* IRQ Access */
struct ksz_irq girq;
struct ksz_ptp_data ptp_data;
+
+ struct net_device *hsr_dev; /* HSR */
+ u8 hsr_ports;
};

/* List of supported models */
--
2.20.1