Re: MCIMX6UL EVK QEMU Ethernet

[Jean-Christophe DUBOIS]

Hello Sean,

I believe that one problem might be that the Ethernet PHY implementation 
is not "complete" in Qemu.

Actually the i.MX FEC driver implement a PHY (LAN911x from SMSC borrowed 
from another Qemu Ethernet emulator) that is not present on the i.MX6UL 
EVK board (it has a micrel PHY)

With your actual device tree the linux kernel is certainly expecting 
that when a link state changes, it get notified by the PHY through some 
GPIO/interrupt and then can react to this (as most PHY do today).

The wiring between the Ethernet PHY device and the processor GPIO is not 
implemented in Qemu (even if the LAN911X would be able to raise an 
interrupt on event, but anyway this particular PHY is not even in your 
device tree).

Therefore your linux kernel never get notified when the PHY get the link 
up (and it does get to this state by default).

So I believe you would have a better chance if you were disabling the 
interrupt from the PHY inside the kernel (through the DTS tree) to get 
to poling mode.

As a matter of fact, for an embedded application using µCOS (not linux), 
I recently had to use the generic µCOS PHY driver (limited to IEEE 
defined registers) that run in polling mode to get it working on Qemu.

So I think you should tweak your device tree to change the way linux 
handle the PHY so that it default to polling mode.

On a related note, the imx_fec emulator expect the PHY to be the first 
device (0) on the MDIO bus (and ignore any request for other devices on 
the MDIO bus). But in the actual linux DTS tree the 2 PHY devices are at 
location (1) and (2). I have a patch lying around to address this point.

JC

Le 02/06/2020 à 12:45, Sean Nyekjaer a écrit :
> Hi
>
>
>
> I'm very new to QEMU and having trouble with the iMX6ul EVK QEMU variant.
>
>
>
> We are starting QEMU with:
>
> % qemu-system-arm \
>
>
> -d trace:usb_port_attach \
>
>
> -machine mcimx6ul-evk \
>
>
> -m 256 \
>
>
> -no-reboot \
>
>
> -nographic \
>
>
> -serial mon:stdio \
>
>
> -kernel ./zImage \
>
>
> -drive 
> if=sd,id=sd0,format=raw,file=./cc-image-dev-iwg26-20200505081306.rootfs.wic 
> \
>
>
> -device sd-card,id=sd0 \
>
>
> -dtb ./imx6ul-14x14-evk.dtb \
>
>
> -append "root=/dev/mmcblk0p3 ro quiet 
> systemd.setenv=SYSTEMD_FSTAB=/etc/fstab.qemu ip=::::qemu::none" \
>
>
> -nic 
> user,mac=02:ca:fe:f0:0d:01,id=u1,net=192.168.60.0/24,dhcpstart=192.168.60.9 
> \
>
>
> -nic 
> user,mac=02:ca:fe:f0:0d:02,id=u2,net=192.168.70.0/24,dhcpstart=192.168.70.9
>
>
>
> But the Ethernet devices never gets a "link up"
>
>
>
> root@qemu:/data/root# ip link
>
>
>
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
> mode DEFAULT group default qlen 1000
>
>
>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>
>
> 2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel 
> state DOWN mode DEFAULT group default qlen 1000
>
>
>     link/ether 02:ca:fe:f0:0d:02 brd ff:ff:ff:ff:ff:ff
>
>
> 3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel 
> state DOWN mode DEFAULT group default qlen 1000
>
>     link/ether 02:ca:fe:f0:0d:01 brd ff:ff:ff:ff:ff:ff
>
>
>
>
>
> I have tried with a 4.19.x and a 5.6 kernel.
>
> Qemu v4.2 and v5.0
>
>
>
> Can you steer me in the correct direction?
>
>
> Best regards,
> Sean Nyekjaer