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References: <20200720113740.353479-1-vaibhavgupta40@gmail.com> <20200727085621.GL12965@vkoul-mobl>
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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Mon, 27 Jul 2020 14:19:14 +0300
Message-ID: <CAHp75VesTCOffxiy6=HG=g2t4=js3SnTm4LcdrgAGYiNvSS65Q@mail.gmail.com>
Subject: Re: [PATCH v1] dmaengine: pch_dma: use generic power management
To:     Vinod Koul <vkoul@kernel.org>
Cc:     Vaibhav Gupta <vaibhavgupta40@gmail.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Bjorn Helgaas <bjorn@helgaas.com>,
        Vaibhav Gupta <vaibhav.varodek@gmail.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        dmaengine <dmaengine@vger.kernel.org>
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On Mon, Jul 27, 2020 at 1:16 PM Vinod Koul <vkoul@kernel.org> wrote:
> On 20-07-20, 17:07, 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(),
> > 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 dev_get_drvdata() to get drv data.
>
> You are doing too many things in One patch. Do consider splitting them
> up to a change per patch. for example using __maybe could be one patch,
> removing code is suspend-resume callbacks would be other one.

Vinod, while I completely agree with you in general, in this case it
would make more unnecessary churn and will be rather unhelpful in all
ways: for the contributor to do this work, for the reader to collect
all the pieces. It also will be a bisectability issue, because the
#ifdeffery replacement (IIRC you need to move from CONFIG_PM to
CONFIG_PM_SLEEP). I really don't see any advantages of the splitting
here.

> > Compile-tested only.
>
> I would like to see some testing before we merge this

I have hardware to test (Intel Minnowboard v1) but have no time. And
taking into account that I did similar changes for many other drivers,
I can give my
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
and take responsibility if somebody complains in the future (I don't
believe it will be one).

P.S. Another scenario if Vaibhav can find that board (there were
dozens of thousands at least produced and floating on the second hand
market) and test himself. It may be good since he touches the full lot
of PCH (EGT20) drivers.

> > Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> > ---
> >  drivers/dma/pch_dma.c | 35 +++++++++--------------------------
> >  1 file changed, 9 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/dma/pch_dma.c b/drivers/dma/pch_dma.c
> > index a3b0b4c56a19..e93005837e3f 100644
> > --- a/drivers/dma/pch_dma.c
> > +++ b/drivers/dma/pch_dma.c
> > @@ -735,8 +735,7 @@ static irqreturn_t pd_irq(int irq, void *devid)
> >       return ret0 | ret2;
> >  }
> >
> > -#ifdef       CONFIG_PM
> > -static void pch_dma_save_regs(struct pch_dma *pd)
> > +static void __maybe_unused pch_dma_save_regs(struct pch_dma *pd)
> >  {
> >       struct pch_dma_chan *pd_chan;
> >       struct dma_chan *chan, *_c;
> > @@ -759,7 +758,7 @@ static void pch_dma_save_regs(struct pch_dma *pd)
> >       }
> >  }
> >
> > -static void pch_dma_restore_regs(struct pch_dma *pd)
> > +static void __maybe_unused pch_dma_restore_regs(struct pch_dma *pd)
> >  {
> >       struct pch_dma_chan *pd_chan;
> >       struct dma_chan *chan, *_c;
> > @@ -782,40 +781,25 @@ static void pch_dma_restore_regs(struct pch_dma *pd)
> >       }
> >  }
> >
> > -static int pch_dma_suspend(struct pci_dev *pdev, pm_message_t state)
> > +static int __maybe_unused pch_dma_suspend(struct device *dev)
> >  {
> > -     struct pch_dma *pd = pci_get_drvdata(pdev);
> > +     struct pch_dma *pd = dev_get_drvdata(dev);
> >
> >       if (pd)
> >               pch_dma_save_regs(pd);
> >
> > -     pci_save_state(pdev);
> > -     pci_disable_device(pdev);
> > -     pci_set_power_state(pdev, pci_choose_state(pdev, state));
> > -
> >       return 0;
> >  }
> >
> > -static int pch_dma_resume(struct pci_dev *pdev)
> > +static int __maybe_unused pch_dma_resume(struct device *dev)
> >  {
> > -     struct pch_dma *pd = pci_get_drvdata(pdev);
> > -     int err;
> > -
> > -     pci_set_power_state(pdev, PCI_D0);
> > -     pci_restore_state(pdev);
> > -
> > -     err = pci_enable_device(pdev);
> > -     if (err) {
> > -             dev_dbg(&pdev->dev, "failed to enable device\n");
> > -             return err;
> > -     }
> > +     struct pch_dma *pd = dev_get_drvdata(dev);
> >
> >       if (pd)
> >               pch_dma_restore_regs(pd);
> >
> >       return 0;
> >  }
> > -#endif
> >
> >  static int pch_dma_probe(struct pci_dev *pdev,
> >                                  const struct pci_device_id *id)
> > @@ -993,15 +977,14 @@ static const struct pci_device_id pch_dma_id_table[] = {
> >       { 0, },
> >  };
> >
> > +static SIMPLE_DEV_PM_OPS(pch_dma_pm_ops, pch_dma_suspend, pch_dma_resume);
> > +
> >  static struct pci_driver pch_dma_driver = {
> >       .name           = DRV_NAME,
> >       .id_table       = pch_dma_id_table,
> >       .probe          = pch_dma_probe,
> >       .remove         = pch_dma_remove,
> > -#ifdef CONFIG_PM
> > -     .suspend        = pch_dma_suspend,
> > -     .resume         = pch_dma_resume,
> > -#endif
> > +     .driver.pm      = &pch_dma_pm_ops,
> >  };
> >
> >  module_pci_driver(pch_dma_driver);
> > --
> > 2.27.0
>
> --
> ~Vinod


-- 
With Best Regards,
Andy Shevchenko