[PATCH net v1 0/4] net: usb: lan78xx: accumulated bug fixes

[PATCH net v1 0/4] net: usb: lan78xx: accumulated bug fixes

[Oleksij Rempel]

This series contains a collection of standalone bug fixes for the
Microchip LAN78xx driver, addressing packet handling, TX statistics,
invalid register accesses, and a kernel warning during disconnect.

Oleksij Rempel (4):
  net: usb: lan78xx: fix silent drop of packets with checksum errors
  net: usb: lan78xx: fix TX byte statistics for small packets
  net: usb: lan78xx: skip LTM configuration for LAN7850
  net: usb: lan78xx: fix WARN in __netif_napi_del_locked on disconnect

 drivers/net/usb/lan78xx.c | 12 ++++++++----
 drivers/net/usb/lan78xx.h |  3 +++
 2 files changed, 11 insertions(+), 4 deletions(-)

--
2.47.3

[PATCH net v1 1/4] net: usb: lan78xx: fix silent drop of packets with checksum errors

[Oleksij Rempel]

Do not drop packets with checksum errors at the USB driver level;
pass them to the network stack.

Previously, the driver dropped all packets where the 'Receive Error
Detected' (RED) bit was set, regardless of the specific error type. This
caused packets with only IP or TCP/UDP checksum errors to be dropped
before reaching the kernel, preventing the network stack from accounting
for them or performing software fallback.

Add a mask for hard hardware errors to safely drop genuinely corrupt
frames, while allowing checksum-errored frames to pass with their
ip_summed field explicitly set to CHECKSUM_NONE.

Fixes: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 drivers/net/usb/lan78xx.c | 4 +++-
 drivers/net/usb/lan78xx.h | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index a0021df12fde..1c8f69190378 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3829,6 +3829,7 @@ static void lan78xx_rx_csum_offload(struct lan78xx_net *dev,
 	 */
 	if (!(dev->net->features & NETIF_F_RXCSUM) ||
 	    unlikely(rx_cmd_a & RX_CMD_A_ICSM_) ||
+	    unlikely(rx_cmd_a & RX_CMD_A_CSE_MASK_) ||
 	    ((rx_cmd_a & RX_CMD_A_FVTG_) &&
 	     !(dev->net->features & NETIF_F_HW_VLAN_CTAG_RX))) {
 		skb->ip_summed = CHECKSUM_NONE;
@@ -3901,7 +3902,8 @@ static int lan78xx_rx(struct lan78xx_net *dev, struct sk_buff *skb,
 			return 0;
 		}
 
-		if (unlikely(rx_cmd_a & RX_CMD_A_RED_)) {
+		if (unlikely(rx_cmd_a & RX_CMD_A_RED_) &&
+		    (rx_cmd_a & RX_CMD_A_RX_HARD_ERRS_MASK_)) {
 			netif_dbg(dev, rx_err, dev->net,
 				  "Error rx_cmd_a=0x%08x", rx_cmd_a);
 		} else {
diff --git a/drivers/net/usb/lan78xx.h b/drivers/net/usb/lan78xx.h
index 968e5e5faee0..17a934acff3d 100644
--- a/drivers/net/usb/lan78xx.h
+++ b/drivers/net/usb/lan78xx.h
@@ -74,6 +74,9 @@
 #define RX_CMD_A_ICSM_			(0x00004000)
 #define RX_CMD_A_LEN_MASK_		(0x00003FFF)
 
+#define RX_CMD_A_RX_HARD_ERRS_MASK_ \
+	(RX_CMD_A_RX_ERRS_MASK_ & ~RX_CMD_A_CSE_MASK_)
+
 /* Rx Command B */
 #define RX_CMD_B_CSUM_SHIFT_		(16)
 #define RX_CMD_B_CSUM_MASK_		(0xFFFF0000)
-- 
2.47.3

[PATCH net v1 2/4] net: usb: lan78xx: fix TX byte statistics for small packets

[Oleksij Rempel]

Account for hardware auto-padding in TX byte counters to reflect actual
wire traffic.

The LAN7850 hardware automatically pads undersized frames to the minimum
Ethernet frame length (ETH_ZLEN, 60 bytes). However, the driver tracks
the network statistics based on the unpadded socket buffer length. This
results in the tx_bytes counter under-reporting the actual physical
bytes placed on the Ethernet wire for small packets (like short ARP or
ICMP requests).

Use max_t() to ensure the transmission statistics accurately account for
the hardware-generated padding.

Fixes: d383216a7efe ("lan78xx: Introduce Tx URB processing improvements")
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 drivers/net/usb/lan78xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 1c8f69190378..507dbcf3b7b0 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -4178,7 +4178,7 @@ static struct skb_data *lan78xx_tx_buf_fill(struct lan78xx_net *dev,
 		}
 
 		tx_data += len;
-		entry->length += len;
+		entry->length += max_t(unsigned int, len, ETH_ZLEN);
 		entry->num_of_packet += skb_shinfo(skb)->gso_segs ?: 1;
 
 		dev_kfree_skb_any(skb);
-- 
2.47.3

[PATCH net v1 3/4] net: usb: lan78xx: skip LTM configuration for LAN7850

[Oleksij Rempel]

Do not configure Latency Tolerance Messaging (LTM) on USB 2.0 hardware.

The LAN7850 is a High-Speed (USB 2.0) only device and does not support
SuperSpeed features like LTM. Currently, the driver unconditionally
attempts to configure LTM registers during initialization. On the
LAN7850, these registers do not exist, resulting in writes to invalid
or undocumented memory space.

This issue was identified during a port to the regmap API with strict
register validation enabled. While no functional issues or crashes have
been observed from these invalid writes, bypassing LTM initialization
on the LAN7850 ensures the driver strictly adheres to the hardware's
valid register map.

Fixes: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 drivers/net/usb/lan78xx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 507dbcf3b7b0..f8558b87eaec 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3119,6 +3119,10 @@ static int lan78xx_init_ltm(struct lan78xx_net *dev)
 	int ret;
 	u32 buf;
 
+	/* LAN7850 is USB 2.0 and does not support LTM */
+	if (dev->chipid == ID_REV_CHIP_ID_7850_)
+		return 0;
+
 	ret = lan78xx_read_reg(dev, USB_CFG1, &buf);
 	if (ret < 0)
 		goto init_ltm_failed;
-- 
2.47.3

[PATCH net v1 4/4] net: usb: lan78xx: fix WARN in __netif_napi_del_locked on disconnect

[Oleksij Rempel]

Remove redundant netif_napi_del() call from disconnect path.

A WARN may be triggered in __netif_napi_del_locked() during USB device
disconnect:

  WARNING: CPU: 0 PID: 11 at net/core/dev.c:7417 __netif_napi_del_locked+0x2b4/0x350

This happens because netif_napi_del() is called in the disconnect path while
NAPI is still enabled. However, it is not necessary to call netif_napi_del()
explicitly, since unregister_netdev() will handle NAPI teardown automatically
and safely. Removing the redundant call avoids triggering the warning.

Full trace:
 lan78xx 1-1:1.0 enu1: Failed to read register index 0x000000c4. ret = -ENODEV
 lan78xx 1-1:1.0 enu1: Failed to set MAC down with error -ENODEV
 lan78xx 1-1:1.0 enu1: Link is Down
 lan78xx 1-1:1.0 enu1: Failed to read register index 0x00000120. ret = -ENODEV
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 11 at net/core/dev.c:7417 __netif_napi_del_locked+0x2b4/0x350
 Modules linked in: flexcan can_dev fuse
 CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 6.16.0-rc2-00624-ge926949dab03 #9 PREEMPT
 Hardware name: SKOV IMX8MP CPU revC - bd500 (DT)
 Workqueue: usb_hub_wq hub_event
 pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : __netif_napi_del_locked+0x2b4/0x350
 lr : __netif_napi_del_locked+0x7c/0x350
 sp : ffffffc085b673c0
 x29: ffffffc085b673c0 x28: ffffff800b7f2000 x27: ffffff800b7f20d8
 x26: ffffff80110bcf58 x25: ffffff80110bd978 x24: 1ffffff0022179eb
 x23: ffffff80110bc000 x22: ffffff800b7f5000 x21: ffffff80110bc000
 x20: ffffff80110bcf38 x19: ffffff80110bcf28 x18: dfffffc000000000
 x17: ffffffc081578940 x16: ffffffc08284cee0 x15: 0000000000000028
 x14: 0000000000000006 x13: 0000000000040000 x12: ffffffb0022179e8
 x11: 1ffffff0022179e7 x10: ffffffb0022179e7 x9 : dfffffc000000000
 x8 : 0000004ffdde8619 x7 : ffffff80110bcf3f x6 : 0000000000000001
 x5 : ffffff80110bcf38 x4 : ffffff80110bcf38 x3 : 0000000000000000
 x2 : 0000000000000000 x1 : 1ffffff0022179e7 x0 : 0000000000000000
 Call trace:
  __netif_napi_del_locked+0x2b4/0x350 (P)
  lan78xx_disconnect+0xf4/0x360
  usb_unbind_interface+0x158/0x718
  device_remove+0x100/0x150
  device_release_driver_internal+0x308/0x478
  device_release_driver+0x1c/0x30
  bus_remove_device+0x1a8/0x368
  device_del+0x2e0/0x7b0
  usb_disable_device+0x244/0x540
  usb_disconnect+0x220/0x758
  hub_event+0x105c/0x35e0
  process_one_work+0x760/0x17b0
  worker_thread+0x768/0xce8
  kthread+0x3bc/0x690
  ret_from_fork+0x10/0x20
 irq event stamp: 211604
 hardirqs last  enabled at (211603): [<ffffffc0828cc9ec>] _raw_spin_unlock_irqrestore+0x84/0x98
 hardirqs last disabled at (211604): [<ffffffc0828a9a84>] el1_dbg+0x24/0x80
 softirqs last  enabled at (211296): [<ffffffc080095f10>] handle_softirqs+0x820/0xbc8
 softirqs last disabled at (210993): [<ffffffc080010288>] __do_softirq+0x18/0x20
 ---[ end trace 0000000000000000 ]---
 lan78xx 1-1:1.0 enu1: failed to kill vid 0081/0

Fixes: e110bc825897 ("net: usb: lan78xx: Convert to PHYLINK for improved PHY and MAC management")
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v2:
- Do not move NAPI enable/disable to link up/down callbacks.
- Remove redundant netif_napi_del() call from disconnect path.
- Update commit message to accurately describe the root cause and solution,
  following feedback from maintainer.
---
 drivers/net/usb/lan78xx.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index f8558b87eaec..19cdf69fa589 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -4552,8 +4552,6 @@ static void lan78xx_disconnect(struct usb_interface *intf)
 	phylink_disconnect_phy(dev->phylink);
 	rtnl_unlock();
 
-	netif_napi_del(&dev->napi);
-
 	unregister_netdev(net);
 
 	timer_shutdown_sync(&dev->stat_monitor);
-- 
2.47.3

Re: [PATCH net v1 0/4] net: usb: lan78xx: accumulated bug fixes

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu,  5 Mar 2026 15:34:25 +0100 you wrote:
> This series contains a collection of standalone bug fixes for the
> Microchip LAN78xx driver, addressing packet handling, TX statistics,
> invalid register accesses, and a kernel warning during disconnect.
> 
> Oleksij Rempel (4):
>   net: usb: lan78xx: fix silent drop of packets with checksum errors
>   net: usb: lan78xx: fix TX byte statistics for small packets
>   net: usb: lan78xx: skip LTM configuration for LAN7850
>   net: usb: lan78xx: fix WARN in __netif_napi_del_locked on disconnect
> 
> [...]

Here is the summary with links:
  - [net,v1,1/4] net: usb: lan78xx: fix silent drop of packets with checksum errors
    https://git.kernel.org/netdev/net/c/e4f774a0cc95
  - [net,v1,2/4] net: usb: lan78xx: fix TX byte statistics for small packets
    https://git.kernel.org/netdev/net/c/50988747c30d
  - [net,v1,3/4] net: usb: lan78xx: skip LTM configuration for LAN7850
    https://git.kernel.org/netdev/net/c/d9cc0e440f06
  - [net,v1,4/4] net: usb: lan78xx: fix WARN in __netif_napi_del_locked on disconnect
    https://git.kernel.org/netdev/net/c/312c816c6bc3

You are awesome, thank you!
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