Re: [PATCH v1] i2c: eg20t: use generic power management

Vaibhav Gupta
2020-08-05T20:13:35Z

On Wed, Aug 05, 2020 at 10:28:32AM -0500, Bjorn Helgaas wrote:
> [update Linus's address, drop Qi's (bounced)]
>
> On Wed, Aug 05, 2020 at 10:23:31AM -0500, Bjorn Helgaas wrote:
> > [+cc Tomoya, Linus, Qi, Ben from e9bc8fa5df1c]
> >
> > On Mon, Jul 20, 2020 at 07:30:32PM +0530, Vaibhav Gupta wrote:
> > > Drivers using legacy PM have to manage PCI states and device's PM states
> > > themselves. They also need to take care of configuration registers.
> > >
> > > With improved and powerful support of generic PM, PCI Core takes care of
> > > above mentioned, device-independent, jobs.
> > >
> > > This driver makes use of PCI helper functions like
> > > pci_save/restore_state(), pci_enable/disable_device(),
> > > pci_enable_wake() and pci_set_power_state() to do required operations. In
> > > generic mode, they are no longer needed.
> > >
> > > Change function parameter in both .suspend() and .resume() to
> > > "struct device*" type. Use to_pci_dev() and dev_get_drvdata() to get
> > > "struct pci_dev*" variable and drv data.
> > >
> > > Compile-tested only.
> > >
> > > Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> > > ---
> > > drivers/i2c/busses/i2c-eg20t.c | 39 ++++++++--------------------------
> > > 1 file changed, 9 insertions(+), 30 deletions(-)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-eg20t.c b/drivers/i2c/busses/i2c-eg20t.c
> > > index 73f139690e4e..c0ddc4cc2ce7 100644
> > > --- a/drivers/i2c/busses/i2c-eg20t.c
> > > +++ b/drivers/i2c/busses/i2c-eg20t.c
> > > @@ -846,11 +846,10 @@ static void pch_i2c_remove(struct pci_dev *pdev)
> > > kfree(adap_info);
> > > }
> > >
> > > -#ifdef CONFIG_PM
> > > -static int pch_i2c_suspend(struct pci_dev *pdev, pm_message_t state)
> > > +static int __maybe_unused pch_i2c_suspend(struct device *dev)
> > > {
> > > - int ret;
> > > int i;
> > > + struct pci_dev *pdev = to_pci_dev(dev);
> > > struct adapter_info *adap_info = pci_get_drvdata(pdev);
> >
> > Why don't you use "adap_info = dev_get_drvdata(dev)" as you did below,
> > so you don't need to_pci_dev()?
> >
Actually, line 870, pch_pci_dbg() again needs "struct pci_dev*" type pointer.
Either way I had to use to_pci_dev(), so defined "pdev" which made less number
of required changes in the code.
> > > void __iomem *p = adap_info->pch_data[0].pch_base_address;
> > >
> > > @@ -872,34 +871,17 @@ static int pch_i2c_suspend(struct pci_dev *pdev, pm_message_t state)
> > > ioread32(p + PCH_I2CSR), ioread32(p + PCH_I2CBUFSTA),
> > > ioread32(p + PCH_I2CESRSTA));
> > >
> > > - ret = pci_save_state(pdev);
> > > -
> > > - if (ret) {
> > > - pch_pci_err(pdev, "pci_save_state\n");
> > > - return ret;
> > > - }
> > > -
> > > - pci_enable_wake(pdev, PCI_D3hot, 0);
> > > - pci_disable_device(pdev);
> > > - pci_set_power_state(pdev, pci_choose_state(pdev, state));
> > > + device_wakeup_disable(dev);
> > >
> > > return 0;
> > > }
> > >
> > > -static int pch_i2c_resume(struct pci_dev *pdev)
> > > +static int __maybe_unused pch_i2c_resume(struct device *dev)
> > > {
> > > int i;
> > > - struct adapter_info *adap_info = pci_get_drvdata(pdev);
> > > -
> > > - pci_set_power_state(pdev, PCI_D0);
> > > - pci_restore_state(pdev);
> > > + struct adapter_info *adap_info = dev_get_drvdata(dev);
> > >
> > > - if (pci_enable_device(pdev) < 0) {
> > > - pch_pci_err(pdev, "pch_i2c_resume:pci_enable_device FAILED\n");
> > > - return -EIO;
> > > - }
> > > -
> > > - pci_enable_wake(pdev, PCI_D3hot, 0);
> > > + device_wakeup_disable(dev);
> >
> > It *looks* wrong to disable wakeup in both suspend and resume. I
> > think the usual pattern is to enable wakeup in suspend and disable it
> > in resume.
> >
> > But it looks like it's been that way since the driver was added by
> > e9bc8fa5df1c ("i2c-eg20t: add driver for Intel EG20T").
> >
> > If the device doesn't support wakeup, I would not expect the driver to
> > mention wakeup at all.
> >
> > In any case, I think it's the right thing for *this* patch to preserve
> > the previous wakeup behavior. Maybe we want a follow-up patch to just
> > remove both device_wakeup_disable() calls?
> >
We have seen this issue earlier in other drivers too. I remember you even
identified and listed them.
The PCI core calls, pci_enable_wake(pci_dev, PCI_D0, false). And if the driver
does not want to enable-wake on suspend, we discussed and concluded that the
calls should be dropped.
I am sending v2, to include dropping wakeup call.

Thanks
Vaibhav Gupta
> > > for (i = 0; i < adap_info->ch_num; i++)
> > > pch_i2c_init(&adap_info->pch_data[i]);
> > > @@ -908,18 +890,15 @@ static int pch_i2c_resume(struct pci_dev *pdev)
> > >
> > > return 0;
> > > }
> > > -#else
> > > -#define pch_i2c_suspend NULL
> > > -#define pch_i2c_resume NULL
> > > -#endif
> > > +
> > > +static SIMPLE_DEV_PM_OPS(pch_i2c_pm_ops, pch_i2c_suspend, pch_i2c_resume);
> > >
> > > static struct pci_driver pch_pcidriver = {
> > > .name = KBUILD_MODNAME,
> > > .id_table = pch_pcidev_id,
> > > .probe = pch_i2c_probe,
> > > .remove = pch_i2c_remove,
> > > - .suspend = pch_i2c_suspend,
> > > - .resume = pch_i2c_resume
> > > + .driver.pm = &pch_i2c_pm_ops,
> > > };
> > >
> > > module_pci_driver(pch_pcidriver);
> > > --
> > > 2.27.0
> > >