netdev - Re: [PATCH] ravb: add wake-on-lan support via magic packet

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Date:   Tue, 16 May 2017 14:16:04 +0200
From:   Niklas Söderlund 
        <niklas.soderlund@...natech.se>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
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,

On 2017-05-16 13:36:21 +0200, Geert Uytterhoeven wrote:
> Hi Simon,
> 
> On Tue, May 16, 2017 at 1:01 PM, Simon Horman <horms@...ge.net.au> wrote:
> > On Tue, May 16, 2017 at 11:07:34AM +0200, Geert Uytterhoeven wrote:
> >> On Tue, May 16, 2017 at 11:02 AM, Niklas Söderlund
> >> <niklas.soderlund@...natech.se> wrote:
> >> >> > Whit all this being said I still like to withdraw this patch as I found
> >> >> > another fault with it, ravb_wol_restore() will unconditionally be called
> >> >> > while ravb_wol_setup() will only be called if netif_running(ndev). This
> >> >> > is en easy fix and I will send out a v2 once we figure out what to do
> >> >> > about the clock.
> >> >>
> >> >> The clock issue is external to the ravb driver. If it works with
> >> >> s2idle, it should
> >> >> be OK.
> >> >
> >> > Do you think it's a good idea to move ahead with a v2 of the ravb WoL
> >> > patch to fix the unrelated issue and aim for it to be picked up prior to
> >> > suspend/resume support is added to the CPG/MSSR?
> >>
> >> Sure.
> >>
> >> It can still be used on R-Car Gen2, where we're not s*d by mandatory PSCI.
> >
> > 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
> 
> "priv->chip_id != RCAR_GEN3". However, as we don't have RAVB enabled
> on any R-Car Gen2 board, its use is limited.

I agree that it's not so useful to enable this on Gen2 only.

> 
> > 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 :-)

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?

> 
> 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

-- 
Regards,
Niklas Söderlund