linux-kernel - Re: [PATCH v1] dmaengine: pch_dma: use generic power management

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Date:   Mon, 27 Jul 2020 18:38:09 +0530
From:   Vaibhav Gupta <vaibhavgupta40@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Vinod Koul <vkoul@...nel.org>, Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Helgaas <bjorn@...gaas.com>,
        Vaibhav Gupta <vaibhav.varodek@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        dmaengine <dmaengine@...r.kernel.org>
Subject: Re: [PATCH v1] dmaengine: pch_dma: use generic power management

On Mon, Jul 27, 2020 at 02:19:14PM +0300, Andy Shevchenko wrote:
> On Mon, Jul 27, 2020 at 1:16 PM Vinod Koul <vkoul@...nel.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@...il.com>
> and take responsibility if somebody complains in the future (I don't
> believe it will be one).
>
Thanks! :D 
> 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.
> 
I cannot promise, but surely will try to get my hands on it :)

Thanks
Vaibhav Gupta
> > > Signed-off-by: Vaibhav Gupta <vaibhavgupta40@...il.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