Re: [PATCH net v2] net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed

[Florian Fainelli <f.fainelli@gmail.com>]

On 5/7/2020 3:03 AM, Marek Szyprowski wrote:
> Hi
> 
> On 07.05.2020 11:46, Marek Szyprowski wrote:
>> On 25.02.2020 14:11, Nicolas Saenz Julienne wrote:
>>> Outdated Raspberry Pi 4 firmware might configure the external PHY as
>>> rgmii although the kernel currently sets it as rgmii-rxid. This makes
>>> connections unreliable as ID_MODE_DIS is left enabled. To avoid this,
>>> explicitly clear that bit whenever we don't need it.
>>>
>>> Fixes: da38802211cc ("net: bcmgenet: Add RGMII_RXID support")
>>> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
>>
>> I've finally bisected the network issue I have on my RPi4 used for 
>> testing mainline builds. The bisect pointed to this patch. Once it got 
>> applied in v5.7-rc1, the networking is broken on my RPi4 in ARM32bit 
>> mode and kernel compiled from bcm2835_defconfig. I'm using u-boot to 
>> tftp zImage/dtb/initrd there. After reverting this patch network is 
>> working fine again. The strange thing is that networking works fine if 
>> kernel is compiled from multi_v7_defconfig but I don't see any obvious 
>> difference there.
>>
>> I'm not sure if u-boot is responsible for this break, but kernel 
>> definitely should be able to properly reset the hardware to the valid 
>> state.
>>
>> I can provide more information, just let me know what is needed. Here 
>> is the log, I hope it helps:
>>
>> [   11.881784] bcmgenet fd580000.ethernet eth0: Link is Up - 
>> 1Gbps/Full - flow control off
>> [   11.889935] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
>>
>> root@target:~# ping host
>> PING host (192.168.100.1) 56(84) bytes of data.
>> From 192.168.100.53 icmp_seq=1 Destination Host Unreachable
>> ...
> 
> Okay, I've played a bit more with this and found that enabling 
> CONFIG_BROADCOM_PHY fixes this network issue. I wonder if Genet driver 
> should simply select CONFIG_BROADCOM_PHY the same way as it selects 
> CONFIG_BCM7XXX_PHY.

Historically GENET has been deployed with an internal PHY and this is
still 90% of the GENET users out there on classic Broadcom STB
platforms, not counting the 2711. For external PHYs, there is a variety
of options here, so selecting CONFIG_BROADCOM_PHY would be just one of
the possibilities, I would rather fix this with the bcm2835_defconfig
and multi_v7_defconfig update. Would that work for you?
-- 
Florian