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

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Message-ID: <9abe58c4-a788-e07d-f281-847ee5b9fcf3@nvidia.com>
Date:   Thu, 22 Apr 2021 18:00:13 +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 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].

> Is power to the Ethernet MAC turned off in this suspend state, in which
> case could we be missing an essential register programming stage?

It seems to be more of a sequencing issue rather than a power issue.

I have also ran 2000 suspend cycles on our Tegra platform without
Joakim's patch to see how stable suspend is on this platform. I did not
see any failures in 2000 cycles and so it is not evident to me that the
problem that Joakim is trying to fix is seen on devices such as Tegra.
Admittedly, if it is hard to reproduce, then it is possible we have not
seen it yet.

Jon

[0]
https://lore.kernel.org/netdev/e4864046-e52f-63b6-a490-74c3cd8045f4@nvidia.com/

-- 
nvpublic