netdev - Re: [PATCH 2/2] net: wwan: iosm: Keep device at D0 for s2idle case

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Date:   Tue, 4 Jan 2022 10:23:38 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Kumar, M Chetan" <m.chetan.kumar@...el.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linuxwwan <linuxwwan@...el.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        Sergey Ryazanov <ryazanov.s.a@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Vaibhav Gupta <vaibhavgupta40@...il.com>
Subject: Re: [PATCH 2/2] net: wwan: iosm: Keep device at D0 for s2idle case

On Mon, Jan 3, 2022 at 11:28 PM Kumar, M Chetan
<m.chetan.kumar@...el.com> wrote:
>
> > -----Original Message-----
> > From: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > Sent: Thursday, December 30, 2021 6:31 AM
> > To: Bjorn Helgaas <helgaas@...nel.org>
> > Cc: Kumar, M Chetan <m.chetan.kumar@...el.com>; linuxwwan
> > <linuxwwan@...el.com>; linux-pci@...r.kernel.org; linux-
> > pm@...r.kernel.org; Loic Poulain <loic.poulain@...aro.org>; Sergey
> > Ryazanov <ryazanov.s.a@...il.com>; Johannes Berg
> > <johannes@...solutions.net>; David S. Miller <davem@...emloft.net>;
> > Jakub Kicinski <kuba@...nel.org>; netdev@...r.kernel.org; linux-
> > kernel@...r.kernel.org; Rafael J. Wysocki <rjw@...ysocki.net>; Vaibhav
> > Gupta <vaibhavgupta40@...il.com>
> > Subject: Re: [PATCH 2/2] net: wwan: iosm: Keep device at D0 for s2idle case
> >
> > On Thu, Dec 30, 2021 at 4:18 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > >
> > > [+cc Rafael, Vaibhav]
> > >
> > > On Fri, Dec 24, 2021 at 04:19:14PM +0800, Kai-Heng Feng wrote:
> > > > We are seeing spurious wakeup caused by Intel 7560 WWAN on AMD
> > laptops.
> > > > This prevent those laptops to stay in s2idle state.
> > > >
> > > > From what I can understand, the intention of ipc_pcie_suspend() is
> > > > to put the device to D3cold, and ipc_pcie_suspend_s2idle() is to
> > > > keep the device at D0. However, the device can still be put to
> > > > D3hot/D3cold by PCI core.
> > > >
> > > > So explicitly let PCI core know this device should stay at D0, to
> > > > solve the spurious wakeup.
>
> Did you get a chance to check the cause of spurious wakeup ? Was there any
> information device is trying to send while platform is entering suspend/
> host sw missed to unsubscribe certain notifications which resulted in wake event.

Can you please let me know how to check it?

>
> In our internal test (x86 platform) we had not noticed such spurious wakeup but would
> like to cross check by running few more tests.

Sure, let me know what tests you want me to run.

>
> > > >
> > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > > > ---
> > > >  drivers/net/wwan/iosm/iosm_ipc_pcie.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > > > b/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > > > index d73894e2a84ed..af1d0e837fe99 100644
> > > > --- a/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > > > +++ b/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > > > @@ -340,6 +340,9 @@ static int __maybe_unused
> > > > ipc_pcie_suspend_s2idle(struct iosm_pcie *ipc_pcie)
> > > >
> > > >       ipc_imem_pm_s2idle_sleep(ipc_pcie->imem, true);
> > > >
> > > > +     /* Let PCI core know this device should stay at D0 */
> > > > +     pci_save_state(ipc_pcie->pci);
> > >
> > > This is a weird and non-obvious way to say "this device should stay at
> > > D0".  It's also fairly expensive since pci_save_state() does a lot of
> > > slow PCI config reads.
> >
> > Yes, so I was waiting for feedback from IOSM devs what's the expected PCI
> > state for the s2idle case.
>
> D3 is the expected state.

Is it D3hot or D3cold?

Kai-Heng

>
> > Dave, can you drop it from netdev until IOSM devs confirm this patch is
> > correct?
>
> Dave, please drop this patch from netdev.