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Subject[PATCH net-next v2 1/1] net: dsa: microchip: ksz9477: implement MTU configuration
Date
This chips supports two ways to configure max MTU size:
- by setting SW_LEGAL_PACKET_DISABLE bit: if this bit is 0 allowed packed size
will be between 64 and bytes 1518. If this bit is 1, it will accept
packets up to 2000 bytes.
- by setting SW_JUMBO_PACKET bit. If this bit is set, the chip will
ignore SW_LEGAL_PACKET_DISABLE value and use REG_SW_MTU__2 register to
configure MTU size.

Current driver has disabled SW_JUMBO_PACKET bit and activates
SW_LEGAL_PACKET_DISABLE. So the switch will pass all packets up to 2000 without
any way to configure it.

By providing port_change_mtu we are switch to SW_JUMBO_PACKET way and will
be able to configure MTU up to ~9000.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v2:
- rename max_mtu to max_frame and new_mtu to frame_size
- use max() instead of if(>)
---
drivers/net/dsa/microchip/ksz9477.c | 40 +++++++++++++++++++++++--
drivers/net/dsa/microchip/ksz9477_reg.h | 4 +++
drivers/net/dsa/microchip/ksz_common.h | 1 +
3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
index 18ffc8ded7ee..5c5f78cb970e 100644
--- a/drivers/net/dsa/microchip/ksz9477.c
+++ b/drivers/net/dsa/microchip/ksz9477.c
@@ -11,6 +11,7 @@
#include <linux/platform_data/microchip-ksz.h>
#include <linux/phy.h>
#include <linux/if_bridge.h>
+#include <linux/if_vlan.h>
#include <net/dsa.h>
#include <net/switchdev.h>

@@ -182,6 +183,33 @@ static void ksz9477_port_cfg32(struct ksz_device *dev, int port, int offset,
bits, set ? bits : 0);
}

+static int ksz9477_change_mtu(struct dsa_switch *ds, int port, int mtu)
+{
+ struct ksz_device *dev = ds->priv;
+ u16 frame_size, max_frame = 0;
+ int i;
+
+ frame_size = mtu + ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN;
+
+ if (dsa_is_cpu_port(ds, port))
+ frame_size += KSZ9477_INGRESS_TAG_LEN;
+
+ /* Cache the per-port MTU setting */
+ dev->ports[port].max_frame = frame_size;
+
+ for (i = 0; i < dev->port_cnt; i++)
+ max_frame = max(max_frame, dev->ports[i].max_frame);
+
+ return regmap_update_bits(dev->regmap[1], REG_SW_MTU__2,
+ REG_SW_MTU_MASK, max_frame);
+}
+
+static int ksz9477_max_mtu(struct dsa_switch *ds, int port)
+{
+ return KSZ9477_MAX_FRAME_SIZE - ETH_HLEN - ETH_FCS_LEN - VLAN_HLEN -
+ KSZ9477_INGRESS_TAG_LEN;
+}
+
static int ksz9477_wait_vlan_ctrl_ready(struct ksz_device *dev)
{
unsigned int val;
@@ -1412,8 +1440,14 @@ static int ksz9477_setup(struct dsa_switch *ds)
/* Do not work correctly with tail tagging. */
ksz_cfg(dev, REG_SW_MAC_CTRL_0, SW_CHECK_LENGTH, false);

- /* accept packet up to 2000bytes */
- ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_LEGAL_PACKET_DISABLE, true);
+ /* Enable REG_SW_MTU__2 reg by setting SW_JUMBO_PACKET */
+ ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_JUMBO_PACKET, true);
+
+ /* Now we can configure default MTU value */
+ ret = regmap_update_bits(dev->regmap[1], REG_SW_MTU__2, REG_SW_MTU_MASK,
+ VLAN_ETH_FRAME_LEN + ETH_FCS_LEN);
+ if (ret)
+ return ret;

ksz9477_config_cpu_port(ds);

@@ -1460,6 +1494,8 @@ static const struct dsa_switch_ops ksz9477_switch_ops = {
.port_mirror_add = ksz9477_port_mirror_add,
.port_mirror_del = ksz9477_port_mirror_del,
.get_stats64 = ksz9477_get_stats64,
+ .port_change_mtu = ksz9477_change_mtu,
+ .port_max_mtu = ksz9477_max_mtu,
};

static u32 ksz9477_get_port_addr(int port, int offset)
diff --git a/drivers/net/dsa/microchip/ksz9477_reg.h b/drivers/net/dsa/microchip/ksz9477_reg.h
index 16939f29faa5..2278e763ee3e 100644
--- a/drivers/net/dsa/microchip/ksz9477_reg.h
+++ b/drivers/net/dsa/microchip/ksz9477_reg.h
@@ -176,6 +176,7 @@
#define REG_SW_MAC_ADDR_5 0x0307

#define REG_SW_MTU__2 0x0308
+#define REG_SW_MTU_MASK GENMASK(13, 0)

#define REG_SW_ISP_TPID__2 0x030A

@@ -1662,4 +1663,7 @@
/* 148,800 frames * 67 ms / 100 */
#define BROADCAST_STORM_VALUE 9969

+#define KSZ9477_INGRESS_TAG_LEN 2
+#define KSZ9477_MAX_FRAME_SIZE 9000
+
#endif /* KSZ9477_REGS_H */
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index c6fa487fb006..739365bfceb2 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -41,6 +41,7 @@ struct ksz_port {

struct ksz_port_mib mib;
phy_interface_t interface;
+ u16 max_frame;
};

struct ksz_device {
--
2.30.2
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