[Linux-kernel-mentees] [PATCH v1] ethernet: intel: e1000: Convert to dev_pm_ops

Bjorn Helgaas helgaas at kernel.org
Fri May 1 21:45:20 UTC 2020


On Fri, May 01, 2020 at 09:19:00PM +0000, Kirsher, Jeffrey T wrote:
> > -----Original Message-----
> > From: Bjorn Helgaas <helgaas at kernel.org>
> > Sent: Friday, May 1, 2020 13:58
> > To: Vaibhav Gupta <vaibhavgupta40 at gmail.com>
> > Cc: linux-kernel-mentees at lists.linuxfoundation.org; bjorn at helgaas.com;
> > skhan at linuxfoundation.org; rjw at rjwysocki.net; Kirsher, Jeffrey T
> > <jeffrey.t.kirsher at intel.com>; Brandeburg, Jesse
> > <jesse.brandeburg at intel.com>
> > Subject: Re: [Linux-kernel-mentees] [PATCH v1] ethernet: intel: e1000: Convert
> > to dev_pm_ops
> > 
> > [+cc Jeff, Jesse]
> > 
> > On Fri, Apr 10, 2020 at 06:14:19PM +0530, Vaibhav Gupta wrote:
> > > Convert the legacy callback .suspend() and .resume() to the generic
> > > ones.
> > >
> > > Signed-off-by: Vaibhav Gupta <vaibhavgupta40 at gmail.com>
> > > ---
> > >  drivers/net/ethernet/intel/e1000/e1000_main.c | 47
> > > +++++--------------
> > >  1 file changed, 12 insertions(+), 35 deletions(-)
> [Kirsher, Jeffrey T] 
> 
> Was there a reason why this patch was not at least CC'd to
> intel-wired-lan at lists.osuosl.org mailing list for all Intel wired
> LAN driver changes?  Thank you Bjorn for at least adding Jesse and
> myself to the thread.

Don't worry, this is potentially part of a mentoring project, and
we're just trying to shake out trivial issues first before throwing
Vaibhav straight into the lions' den, so to speak.

> On top of the potential issues Bjorn pointed out, this could cause
> regression issues that can not fully be validated since this driver
> is really old and all supported devices may no longer be available
> to test against.

Understood.  The problem we're trying to solve is that the PCI
core carries quite a bit of code to support both the legacy power
management and the "new" (now 10 year-old) generic scheme.  That
extra code is its own source of bugs since it's hard to keep both
paths up to date and tested.

> > > diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c
> > > b/drivers/net/ethernet/intel/e1000/e1000_main.c
> > > index 2bced34c19ba..09a6ef46be96 100644
> > > --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
> > > +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
> > > @@ -152,8 +152,8 @@ static int e1000_vlan_rx_kill_vid(struct
> > > net_device *netdev,  static void e1000_restore_vlan(struct
> > > e1000_adapter *adapter);
> > >
> > >  #ifdef CONFIG_PM
> > > -static int e1000_suspend(struct pci_dev *pdev, pm_message_t state);
> > > -static int e1000_resume(struct pci_dev *pdev);
> > > +static int e1000_suspend(struct device *dev); static int
> > > +e1000_resume(struct device *dev);
> > >  #endif
> > >  static void e1000_shutdown(struct pci_dev *pdev);
> > >
> > > @@ -179,16 +179,16 @@ static const struct pci_error_handlers
> > e1000_err_handler = {
> > >  	.resume = e1000_io_resume,
> > >  };
> > >
> > > +static SIMPLE_DEV_PM_OPS(e1000_pm_ops, e1000_suspend,
> > e1000_resume);
> > > +
> > >  static struct pci_driver e1000_driver = {
> > >  	.name     = e1000_driver_name,
> > >  	.id_table = e1000_pci_tbl,
> > >  	.probe    = e1000_probe,
> > >  	.remove   = e1000_remove,
> > > -#ifdef CONFIG_PM
> > > -	/* Power Management Hooks */
> > > -	.suspend  = e1000_suspend,
> > > -	.resume   = e1000_resume,
> > > -#endif
> > > +	.driver = {
> > > +		.pm = &e1000_pm_ops,
> > > +	},
> > >  	.shutdown = e1000_shutdown,
> > >  	.err_handler = &e1000_err_handler
> > >  };
> > > @@ -5052,9 +5052,6 @@ static int __e1000_shutdown(struct pci_dev *pdev,
> > bool *enable_wake)
> > >  	struct e1000_hw *hw = &adapter->hw;
> > >  	u32 ctrl, ctrl_ext, rctl, status;
> > >  	u32 wufc = adapter->wol;
> > > -#ifdef CONFIG_PM
> > > -	int retval = 0;
> > > -#endif
> > >
> > >  	netif_device_detach(netdev);
> > >
> > > @@ -5068,12 +5065,6 @@ static int __e1000_shutdown(struct pci_dev
> > *pdev, bool *enable_wake)
> > >  		e1000_down(adapter);
> > >  	}
> > >
> > > -#ifdef CONFIG_PM
> > > -	retval = pci_save_state(pdev);
> > > -	if (retval)
> > > -		return retval;
> > > -#endif
> > > -
> > >  	status = er32(STATUS);
> > >  	if (status & E1000_STATUS_LU)
> > >  		wufc &= ~E1000_WUFC_LNKC;
> > > @@ -5135,36 +5126,22 @@ static int __e1000_shutdown(struct pci_dev
> > > *pdev, bool *enable_wake)  }
> > >
> > >  #ifdef CONFIG_PM
> > > -static int e1000_suspend(struct pci_dev *pdev, pm_message_t state)
> > > +static int e1000_suspend(struct device *dev)
> > >  {
> > > -	int retval;
> > > +	struct pci_dev *pdev = to_pci_dev(dev);
> > >  	bool wake;
> > >
> > > -	retval = __e1000_shutdown(pdev, &wake);
> > > -	if (retval)
> > > -		return retval;
> > > -
> > > -	if (wake) {
> > > -		pci_prepare_to_sleep(pdev);
> > > -	} else {
> > > -		pci_wake_from_d3(pdev, false);
> > 
> > I think there's a case where this changes the behavior because we normally set
> > the device wakeup enable to adapter->wol, but the "wake"
> > returned from __e1000_shutdown() is sometimes different.
> > 
> >   e1000_probe
> >     adapter->wol = adapter->eeprom_wol;      # assume adapter->wol == 1
> >     device_set_wakeup_enable(adapter->wol);
> > 
> >   Existing code:
> >     e1000_suspend
> >       __e1000_shutdown(&wake)                # assume returns wake == 0
> >       pci_wake_from_d3(false)
> >         pci_enable_wake(PCI_D3hot, false)    # <-- compare
> > 
> >   New code using generic PM ops:
> >     pci_pm_suspend
> >       e1000_suspend
> >         __e1000_shutdown(&wake)              # returns wake == 0 (ignored)
> >     pci_pm_suspend_noirq
> >       pci_prepare_to_sleep
> >         wakeup = device_may_wakeup()         # returns 1
> >         pci_enable_wake(PCI_D3hot, true)     # <-- different!
> > 
> > I sort of suspect that __e1000_shutdown() should call
> > device_set_wakeup_enable() when it updates the chip's wake-on-lan
> > registers, but the driver maintainers would know better.

If you have any ideas about this, or maybe patterns in newer Intel
drivers that could be followed here, we'd love to hear them.

If you think it's impossible to update e1000 to generic power
management, it'd be useful to know that, too, so we can move on to
other drivers.

> > > -		pci_set_power_state(pdev, PCI_D3hot);
> > > -	}
> > > -
> > > -	return 0;
> > > +	return __e1000_shutdown(pdev, &wake);
> > >  }
> > >
> > > -static int e1000_resume(struct pci_dev *pdev)
> > > +static int e1000_resume(struct device *dev)
> > >  {
> > > +	struct pci_dev *pdev = to_pci_dev(dev);
> > >  	struct net_device *netdev = pci_get_drvdata(pdev);
> > >  	struct e1000_adapter *adapter = netdev_priv(netdev);
> > >  	struct e1000_hw *hw = &adapter->hw;
> > >  	u32 err;
> > >
> > > -	pci_set_power_state(pdev, PCI_D0);
> > > -	pci_restore_state(pdev);
> > > -	pci_save_state(pdev);
> > > -
> > >  	if (adapter->need_ioport)
> > >  		err = pci_enable_device(pdev);
> > >  	else
> > > --
> > > 2.26.0
> > >


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