Date:   Mon, 12 Jun 2017 13:43:04 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Niklas Söderlund <niklas.soderlund@...natech.se>
Cc:     Simon Horman <horms@...ge.net.au>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] ravb: add wake-on-lan support via magic packet

Hi Niklas,

On Mon, Jun 12, 2017 at 1:32 PM, Niklas Söderlund
<niklas.soderlund@...natech.se> wrote:
> On 2017-05-18 10:52:25 +0200, Geert Uytterhoeven wrote:
>> On Tue, May 16, 2017 at 2:16 PM, Niklas Söderlund
>> <niklas.soderlund@...natech.se> wrote:
>> > On 2017-05-16 13:36:21 +0200, Geert Uytterhoeven wrote:
>> >> On Tue, May 16, 2017 at 1:01 PM, Simon Horman <horms@...ge.net.au> wrote:
>> >> > Is there some way for - e.g. the driver - to not enable WoL on Gen3 SoCs
>> >> > until the clock issues is sorted out? I'm quite happy to enable features
>> >> > where they work; not so much where they don't.
>> >>
>> >> Agreed.
>> >>
>> >> One workaround could be to disable/enable the module clock in the WoL
>> >> resume path, to make sure it is enabled.  Once the enable count reaches
>> >> 0, CCF will know it's disabled, and will really enable next time.
>> >> You may need a double disable/double enable though, without testing I
>> >> don't know remember the enable count is 1 or 2 at that point (due to PM
>> >> runtime).
>> >
>> > I thought about this but it feels like such a hack I did not dare
>> > suggest it :-) But at the same time it would be nice to enable WoL for
>> > the s2idle use-case where it works. Only resume from PSCI with WoL
>> > enabled that is broken, and WoL in PSCI suspend will never work :-)
>>
>> Indeed.
>>
>> > How about I add another patch in v2 on-top of this that adds the clock
>> > disable/enable hack? That way it's clear that this is a workaround and
>> > once we have support for suspend/resume in CPG/MSSR just that patch can
>> > be reverted? Or is it cleaner to fold it in to this patch with a big
>> > comment that this is a workaround? Or is it maybe better to hold of on
>> > this until CPG/MSSR supports suspend/resume?
>>
>> Personally, I would have no problems of having the workaround integrated (and
>> documented, of course) in the WoL patch, as it avoids having broken PSCI
>> suspend in between WoL-without-workaround and a separate workaround.
>
> You have now posted '[PATCH/RFC] clk: renesas: cpg-mssr: Restore module
> clock registers during resume' which solves this issue. Do you think it
> would be OK for me to resubmit this patch due to an unrelated fix and
> state that it depends on your patch or do you feel it still would be
> valuable to include a workaround in the RAVB driver as to not make it
> dependent on your patch?

The the module clock restore patch fixes the issue, I think it's too immature
to upstream.  Applying your WoL patch as-is does introduce a regression if
WoL is enabled (although you could debate that it's not a regression, as WoL
couldn't be enabled before, but a generic userspace may try to do that anyway).

If the workaround isn't too ugly, I would include it.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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