linux-kernel - Re: [PATCH net v2] net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB

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Message-ID: <e8526ec5-9a42-4b0a-b517-f9beaea5e8cd@gmx.net>
Date:   Fri, 8 May 2020 19:26:22 +0200
From:   Stefan Wahren <wahrenst@....net>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Doug Berger <opendmb@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net: bcmgenet: Clear ID_MODE_DIS in
 EXT_RGMII_OOB_CTRL when not needed

Hi Marek,

Am 07.05.20 um 12:03 schrieb Marek Szyprowski:
> 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 Outdated Raspberry Pi 4 firmware might configure the external PHY as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@...e.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@...get:~# 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.

thanks for finding this issue. So it seems arm64/defconfig is also affected.

I don't have a strong opinion how to solve this.

Best regards
Stefan

>
> Best regards