linux-kernel - Re: [PATCH] e1000e: Assign DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP

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Date:   Thu, 26 Nov 2020 19:10:54 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "moderated list:INTEL ETHERNET DRIVERS" 
        <intel-wired-lan@...ts.osuosl.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Sasha Neftin <sasha.neftin@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Chen Yu <yu.c.chen@...el.com>
Subject: Re: [PATCH] e1000e: Assign DPM_FLAG_SMART_SUSPEND and
 DPM_FLAG_MAY_SKIP_RESUME to speed up s2ram

On Thu, Nov 26, 2020 at 02:36:42PM +0800, Kai-Heng Feng wrote:
> >> 
> >> What about plugging ethernet cable and using WoL after system is suspended?
> >> Commit "e1000e: Exclude device from suspend direct complete optimization" was to address that scenario.
[cut]
> 
> I don't think this is right.
> Isn't E1000_WUFC_LNKC already set for runtime suspend?
> What if WoL doesn't have it set?
>
After re-taking a look at your description, please let me elaborate more about the scenario.
With this patch applied, and with sysfs wake up disabled, the expected behavior is:

1. If NIC is not runtime suspended:
 1.1 s2ram suspend -> wufc will be set to 0(no WoL settings), suspend(), suspend_late(), suspend_noirq()
 1.2 s2ram resume  -> NIC resumes normaly

2. If NIC is runtime suspended:
 2.1 s2ram suspend -> wufc set to E1000_WUFC_LNKC, skip the subsequent suspend callbacks.
 2.2 s2ram resume -> skip the subsequent resume callbacks.

If between 2.1 and 2.2, the cable is plugged, the user is unable to use WoL to wake up
the system.

But if the sysfs wake up is enabled, the code logic falls into the old path, and
the user can wake up the system via WoL by plugging the cable, and send packages to the
system. Or do I miss something?

thanks,
Chenyu