Re: [PATCH] PCI / PM: Allow runtime PM without callback functions

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Oct 18, 2018 at 03:30:38PM +0300, Jarkko Nikula wrote:
> Allow PCI core to do runtime PM to devices without needing to use dummy
> runtime PM callback functions if there is no need to do anything device
> specific beyond PCI device power state management.
> 
> Implement this by letting core to change device power state during
> runtime PM transitions even if no callback functions are defined.
> 
> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
> Reported-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>

I applied this with Rafael's reviewed-by to pci/misc for v4.20,
thanks!

But I dropped the stable tag because if I understand correctly, the
point of this is to avoid the need for SIMPLE_DEV_PM_OPS() in drivers
that don't need to do anything for PM.

That's worthwhile, but it's not transparently obvious that it would
qualify for a stable backport based on this:

  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst

If there's an argument for adding a stable tag, I'll add it , but that
justification should be explicit in the changelog.

> Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> ---
> This is related to my i2c-i801.c fix thread back in June which I completely
> forgot till now: https://lkml.org/lkml/2018/6/27/642
> Discussion back then was that it should be handled in the PCI PM instead
> of having dummy functions in the drivers. I wanted to respin with a
> patch.
> ---
>  drivers/pci/pci-driver.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index bef17c3fca67..6185b878ede1 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1239,7 +1239,7 @@ static int pci_pm_runtime_suspend(struct device *dev)
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>  	pci_power_t prev = pci_dev->current_state;
> -	int error;
> +	int error = 0;
>  
>  	/*
>  	 * If pci_dev->driver is not set (unbound), we leave the device in D0,
> @@ -1251,11 +1251,9 @@ static int pci_pm_runtime_suspend(struct device *dev)
>  		return 0;
>  	}
>  
> -	if (!pm || !pm->runtime_suspend)
> -		return -ENOSYS;
> -
>  	pci_dev->state_saved = false;
> -	error = pm->runtime_suspend(dev);
> +	if (pm && pm->runtime_suspend)
> +		error = pm->runtime_suspend(dev);
>  	if (error) {
>  		/*
>  		 * -EBUSY and -EAGAIN is used to request the runtime PM core
> @@ -1292,7 +1290,7 @@ static int pci_pm_runtime_suspend(struct device *dev)
>  
>  static int pci_pm_runtime_resume(struct device *dev)
>  {
> -	int rc;
> +	int rc = 0;
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>  
> @@ -1306,14 +1304,12 @@ static int pci_pm_runtime_resume(struct device *dev)
>  	if (!pci_dev->driver)
>  		return 0;
>  
> -	if (!pm || !pm->runtime_resume)
> -		return -ENOSYS;
> -
>  	pci_fixup_device(pci_fixup_resume_early, pci_dev);
>  	pci_enable_wake(pci_dev, PCI_D0, false);
>  	pci_fixup_device(pci_fixup_resume, pci_dev);
>  
> -	rc = pm->runtime_resume(dev);
> +	if (pm && pm->runtime_resume)
> +		rc = pm->runtime_resume(dev);
>  
>  	pci_dev->runtime_d3cold = false;
>  
> -- 
> 2.19.1
> 



[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux