linux-kernel - Re: [Linux-kernel-mentees] [PATCH v2 2/2] realtek/8139cp: Remove Legacy Power Management

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Date:   Wed, 29 Apr 2020 20:02:11 +0530
From:   Vaibhav Gupta <vaibhav.varodek@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Vaibhav Gupta <vaibhavgupta40@...il.com>,
        Shannon Nelson <snelson@...sando.io>,
        Jakub Kicinski <kuba@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Martin Habets <mhabets@...arflare.com>, netdev@...r.kernel.org,
        bjorn@...gaas.com, linux-kernel-mentees@...ts.linuxfoundation.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
        skhan@...uxfoundation.org
Subject: Re: [Linux-kernel-mentees] [PATCH v2 2/2] realtek/8139cp: Remove
 Legacy Power Management

On Tue, 28 Apr 2020 at 22:59, Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Tue, Apr 28, 2020 at 08:13:14PM +0530, Vaibhav Gupta wrote:
> > Upgrade power management from legacy to generic using dev_pm_ops.
> >
> > Add "__maybe_unused" attribute to resume() and susend() callbacks
> > definition to suppress compiler warnings.
> >
> > Generic callback requires an argument of type "struct device*". Hence,
> > convert it to "struct net_device*" using "dev_get_drv_data()" to use
> > it in the callback.
> >
> > Most of the cleaning part is to remove pci_save_state(),
> > pci_set_power_state(), etc power management function calls.
> >
> > Signed-off-by: Vaibhav Gupta <vaibhavgupta40@...il.com>
> > ---
> >  drivers/net/ethernet/realtek/8139cp.c | 25 +++++++------------------
> >  1 file changed, 7 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/realtek/8139cp.c b/drivers/net/ethernet/realtek/8139cp.c
> > index 60d342f82fb3..4f2fb1393966 100644
> > --- a/drivers/net/ethernet/realtek/8139cp.c
> > +++ b/drivers/net/ethernet/realtek/8139cp.c
> > @@ -2054,10 +2054,9 @@ static void cp_remove_one (struct pci_dev *pdev)
> >       free_netdev(dev);
> >  }
> >
> > -#ifdef CONFIG_PM
> > -static int cp_suspend (struct pci_dev *pdev, pm_message_t state)
> > +static int __maybe_unused cp_suspend(struct device *device)
> >  {
> > -     struct net_device *dev = pci_get_drvdata(pdev);
> > +     struct net_device *dev = dev_get_drvdata(device);
> >       struct cp_private *cp = netdev_priv(dev);
> >       unsigned long flags;
> >
> > @@ -2075,16 +2074,12 @@ static int cp_suspend (struct pci_dev *pdev, pm_message_t state)
> >
> >       spin_unlock_irqrestore (&cp->lock, flags);
> >
> > -     pci_save_state(pdev);
> > -     pci_enable_wake(pdev, pci_choose_state(pdev, state), cp->wol_enabled);
>
> This one is a little more interesting because it relies on the driver
> state (cp->wol_enabled).  IIUC, the corresponding pci_enable_wake() in
> the generic path is in pci_prepare_to_sleep() (called from
> pci_pm_suspend_noirq()).
>
> But of course the generic path doesn't look at cp->wol_enabled.  It
> looks at device_may_wakeup(), but I don't know whether there's a
> connection between that and cp->wol_enabled.
I have tested it by just compiling it. I will try to dig a bit more deep into
this and check if it is affecting something (on the basis of code).
The final test has to done with hardware.

-- Vaibhav Gupta
>
> > -     pci_set_power_state(pdev, pci_choose_state(pdev, state));
> > -
> >       return 0;
> >  }
> >
> > -static int cp_resume (struct pci_dev *pdev)
> > +static int __maybe_unused cp_resume(struct device *device)
> >  {
> > -     struct net_device *dev = pci_get_drvdata (pdev);
> > +     struct net_device *dev = dev_get_drvdata(device);
> >       struct cp_private *cp = netdev_priv(dev);
> >       unsigned long flags;
> >
> > @@ -2093,10 +2088,6 @@ static int cp_resume (struct pci_dev *pdev)
> >
> >       netif_device_attach (dev);
> >
> > -     pci_set_power_state(pdev, PCI_D0);
> > -     pci_restore_state(pdev);
> > -     pci_enable_wake(pdev, PCI_D0, 0);
> > -
> >       /* FIXME: sh*t may happen if the Rx ring buffer is depleted */
> >       cp_init_rings_index (cp);
> >       cp_init_hw (cp);
> > @@ -2111,7 +2102,6 @@ static int cp_resume (struct pci_dev *pdev)
> >
> >       return 0;
> >  }
> > -#endif /* CONFIG_PM */
> >
> >  static const struct pci_device_id cp_pci_tbl[] = {
> >          { PCI_DEVICE(PCI_VENDOR_ID_REALTEK,     PCI_DEVICE_ID_REALTEK_8139), },
> > @@ -2120,15 +2110,14 @@ static const struct pci_device_id cp_pci_tbl[] = {
> >  };
> >  MODULE_DEVICE_TABLE(pci, cp_pci_tbl);
> >
> > +static SIMPLE_DEV_PM_OPS(cp_pm_ops, cp_suspend, cp_resume);
> > +
> >  static struct pci_driver cp_driver = {
> >       .name         = DRV_NAME,
> >       .id_table     = cp_pci_tbl,
> >       .probe        = cp_init_one,
> >       .remove       = cp_remove_one,
> > -#ifdef CONFIG_PM
> > -     .resume       = cp_resume,
> > -     .suspend      = cp_suspend,
> > -#endif
> > +     .driver.pm    = &cp_pm_ops,
> >  };
> >
> >  module_pci_driver(cp_driver);
> > --
> > 2.26.2
> >