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

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Date:   Mon, 27 Jul 2020 15:55:03 +0530
From:   Vaibhav Gupta <vaibhavgupta40@...il.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     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@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        dmaengine@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: pch_dma: use generic power management

On Mon, Jul 27, 2020 at 02:26:21PM +0530, Vinod Koul wrote:
> Hi Vaibhav,
> 
> 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.
>
Sure. But I guess just marking of "__maybe_unused" is not some significant
change. All the legacy PCI drivers have .suspend() and .resume() inside
"#ifdef CONFIG_PM" container.
It is only when I am upgrading them one by one to generic, I remove the
container and mark them with the attribute. So it is like a part of complete
generic upgrade.

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