Loopback Configuration Bug in mpfs_ethernet.c

[sastel]

@acassis on nuttx-12.5.0, switching on CONFIG_NET_LOOPBACK to get the lo localhost working breaks eth0 interface so that I can no longer ping the board.

The mpfs_ethernet.c file turns on the NETWORK_CONTROL_LOOPBACK_LOCAL flag in mpfs_macconfig() if CONFIG_NET_LOOPBACK is defined. I think that this is a misunderstanding of what CONFIG_NET_LOOPBACK is for.

config NET_LOOPBACK
    bool "Local loopback"
    select ARCH_HAVE_NETDEV_STATISTICS
    default n
    ---help---
        Add support for the local network loopback device, lo.

Proposed fix is below. I'd like to open a PR and merge this fix if the NuttX developers approve.

diff --git a/arch/risc-v/src/mpfs/mpfs_ethernet.c b/arch/risc-v/src/mpfs/mpfs_ethernet.c
index 382477fa9e..0a5755d354 100644
--- a/arch/risc-v/src/mpfs/mpfs_ethernet.c
+++ b/arch/risc-v/src/mpfs/mpfs_ethernet.c
@@ -3104,7 +3104,7 @@ static int mpfs_macconfig(struct mpfs_ethmac_s *priv)
   net_config |= NETWORK_CONFIG_SGMII_MODE_ENABLE | NETWORK_CONFIG_PCS_SELECT;
 #endif

-#ifdef CONFIG_NET_LOOPBACK
+#ifdef CONFIG_MPFS_MAC_LOOPBACK
   net_control |= NETWORK_CONTROL_LOOPBACK_LOCAL;
 #endif

[acassis]

So, is this PolarFire Loopback something specific of is Ethernet controller? If so your modification seems correct.

@pussuw could you please take a look?

[sastel]

Yes NETWORK_CONTROL_LOOPBACK_LOCAL is a bit in the NETWORK_CONTROL MAC register on MPFS.