netdev - Re: [RFC net-next] net: stmmac: should not modify RX descriptor when STMMAC resume

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Message-ID: <0e6467a0-428a-6520-f012-bdd332a7d7ee@nvidia.com>
Date:   Fri, 23 Apr 2021 14:46:43 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>
CC:     dl-linux-imx <linux-imx@....com>,
        "treding@...dia.com" <treding@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC net-next] net: stmmac: should not modify RX descriptor when
 STMMAC resume


On 22/04/2021 19:20, Florian Fainelli wrote:
> 
> 
> On 4/22/2021 11:18 AM, Jon Hunter wrote:
>>
>> On 22/04/2021 18:32, Florian Fainelli wrote:
>>>
>>>
>>> On 4/22/2021 10:00 AM, Jon Hunter wrote:
>>>>
>>>> On 22/04/2021 17:12, Florian Fainelli wrote:
>>>>
>>>> ...
>>>>
>>>>> What does the resumption failure looks like? Does the stmmac driver
>>>>> successfully resume from your suspend state, but there is no network
>>>>> traffic? Do you have a log by any chance?
>>>>
>>>> The board fails to resume and appears to hang. With regard to the
>>>> original patch I did find that moving the code to re-init the RX buffers
>>>> to before the PHY is enabled did work [0].
>>>
>>> You indicated that you are using a Broadcom PHY, which specific PHY are
>>> you using?
>>>
>>> I suspect that the stmmac is somehow relying on the PHY to provide its
>>> 125MHz RXC clock back to you in order to have its RX logic work correctly.
>>>
>>> One difference between using the Broadcom PHY and the Generic PHY
>>> drivers could be whether your Broadcom PHY driver entry has a
>>> .suspend/.resume callback implemented or not.
>>
>>
>> This board has a BCM89610 and uses the drivers/net/phy/broadcom.c
>> driver. Interestingly I don't see any suspend/resume handlers for this phy.
> 
> Now if you do add .suspend = genphy_suspend and .resume = bcm54xx_resume
> for this PHY entry does it work better?

Thanks for the suggestion. I tried this and this appears to breaking
networking altogether. In other words, the board was not longer able to
request an IP address. I also tried the genphy_resume and the board was
able to get an IP address, but it is still unable to resume from suspend.

Thanks
Jon

-- 
nvpublic