netdev - Re: [PATCH 1/2] net: wwan: iosm: Let PCI core handle PCI power transition

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Date:   Thu, 30 Dec 2021 08:57:42 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     m.chetan.kumar@...el.com, 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,
        Vaibhav Gupta <vaibhavgupta40@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH 1/2] net: wwan: iosm: Let PCI core handle PCI power transition

On Thu, Dec 30, 2021 at 4:12 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> [+cc Rafael, in case you have insight about the PCI_D0 question below;
> Vaibhav, since this is related to your generic PM conversions]
>
> On Fri, Dec 24, 2021 at 04:19:13PM +0800, Kai-Heng Feng wrote:
> > pci_pm_suspend_noirq() and pci_pm_resume_noirq() already handle power
> > transition for system-wide suspend and resume, so it's not necessary to
> > do it in the driver.
>
> I see DaveM has already applied this, but it looks good to me, thanks
> for doing this!
>
> One minor question below...
>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> >  drivers/net/wwan/iosm/iosm_ipc_pcie.c | 49 ++-------------------------
> >  1 file changed, 2 insertions(+), 47 deletions(-)
> >
> > diff --git a/drivers/net/wwan/iosm/iosm_ipc_pcie.c b/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > index 2fe88b8be3481..d73894e2a84ed 100644
> > --- a/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > +++ b/drivers/net/wwan/iosm/iosm_ipc_pcie.c
> > @@ -363,67 +363,22 @@ static int __maybe_unused ipc_pcie_resume_s2idle(struct iosm_pcie *ipc_pcie)
> >
> >  int __maybe_unused ipc_pcie_suspend(struct iosm_pcie *ipc_pcie)
> >  {
> > -     struct pci_dev *pdev;
> > -     int ret;
> > -
> > -     pdev = ipc_pcie->pci;
> > -
> > -     /* Execute D3 one time. */
> > -     if (pdev->current_state != PCI_D0) {
> > -             dev_dbg(ipc_pcie->dev, "done for PM=%d", pdev->current_state);
> > -             return 0;
> > -     }
>
> I don't understand the intent of this early exit, and it's not obvious
> to me that pci_pm_suspend_noirq() bails out early when
> (pdev->current_state != PCI_D0).

Yes, I think this can be removed too. Please let me send v2.

Kai-Heng

>
> >       /* The HAL shall ask the shared memory layer whether D3 is allowed. */
> >       ipc_imem_pm_suspend(ipc_pcie->imem);
> >
> > -     /* Save the PCI configuration space of a device before suspending. */
> > -     ret = pci_save_state(pdev);
> > -
> > -     if (ret) {
> > -             dev_err(ipc_pcie->dev, "pci_save_state error=%d", ret);
> > -             return ret;
> > -     }
> > -
> > -     /* Set the power state of a PCI device.
> > -      * Transition a device to a new power state, using the device's PCI PM
> > -      * registers.
> > -      */
> > -     ret = pci_set_power_state(pdev, PCI_D3cold);
> > -
> > -     if (ret) {
> > -             dev_err(ipc_pcie->dev, "pci_set_power_state error=%d", ret);
> > -             return ret;
> > -     }
> > -
> >       dev_dbg(ipc_pcie->dev, "SUSPEND done");
> > -     return ret;
> > +     return 0;
> >  }
> >
> >  int __maybe_unused ipc_pcie_resume(struct iosm_pcie *ipc_pcie)
> >  {
> > -     int ret;
> > -
> > -     /* Set the power state of a PCI device.
> > -      * Transition a device to a new power state, using the device's PCI PM
> > -      * registers.
> > -      */
> > -     ret = pci_set_power_state(ipc_pcie->pci, PCI_D0);
> > -
> > -     if (ret) {
> > -             dev_err(ipc_pcie->dev, "pci_set_power_state error=%d", ret);
> > -             return ret;
> > -     }
> > -
> > -     pci_restore_state(ipc_pcie->pci);
> > -
> >       /* The HAL shall inform the shared memory layer that the device is
> >        * active.
> >        */
> >       ipc_imem_pm_resume(ipc_pcie->imem);
> >
> >       dev_dbg(ipc_pcie->dev, "RESUME done");
> > -     return ret;
> > +     return 0;
> >  }
> >
> >  static int __maybe_unused ipc_pcie_suspend_cb(struct device *dev)
> > --
> > 2.33.1
> >