netdev - Linux kernel hangs if using RV1108 with MSZ8863 switch with two ports connected

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Date:   Fri, 16 Nov 2018 16:28:29 -0200
From:   Otavio Salvador <otavio.salvador@...ystems.com.br>
To:     netdev@...r.kernel.org, andrew@...n.ch,
        Heiko Stuebner <heiko@...ech.de>, david.choi@...rel.com,
        Andy Yan <andy.yan@...k-chips.com>
Subject: Linux kernel hangs if using RV1108 with MSZ8863 switch with two ports connected

Hi,

I have a custom design based on Rockchip RV1108 that uses an MSZ8863
switch running kernel 4.19.

The dts part is as follows:

&gmac {
pinctrl-names = "default";
pinctrl-0 = <&rmii_pins>;
snps,reset-gpio = <&gpio1 RK_PC1 GPIO_ACTIVE_LOW>;
snps,reset-active-low;
clock_in_out = "output";
status = "okay";
};

RV1108 GMAC is connected to KSZ8863 port 3 and after kernel boots, I
can put an Ethernet cable from my router to the uplink port of
KSZ8863, which makes the RV1108 board and a Linux PC connected to the
other KSZ8863 port to both get IP addresses.

So in this usecase the setup is working fine.

However, if the RV1108 board boots with both Ethernet cables to the
KSZ8863 switch connected, then the kernel silently hangs.

Any suggestions as to what I should do in order to avoid the kernel to
hang with the two Ethernet cables connected?

The system boots fine without any Ethernet cable connected or with
only one Ethernet cable connected.
Here is the log of the system booting with no Ethernet cable connected:
http://dark-code.bulix.org/9kfff9-506410

It is only when both cables are connected that the kernel silently hangs.

Also, with the vendor 3.10 kernel such hang does not happen.

Thanks

-- 
Otavio Salvador                             O.S. Systems
http://www.ossystems.com.br        http://code.ossystems.com.br
Mobile: +55 (53) 9 9981-7854          Mobile: +1 (347) 903-9750