linux-kernel - Re: [PATCH v2 1/2] PCI/PM: refactor pci_pm_suspend

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Date:   Thu, 17 Mar 2022 19:09:40 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     Rajvi Jingar <rajvi.jingar@...el.com>, rafael.j.wysocki@...el.com,
        bhelgaas@...gle.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/2] PCI/PM: refactor pci_pm_suspend_noirq()

Hi Rajvi,

On Thu, 2022-03-17 at 16:31 -0700, Rajvi Jingar wrote:
> The state of the device is saved during pci_pm_suspend_noirq(), if it
> has not already been saved, regardless of the skip_bus_pm flag value. So
> skip_bus_pm check is removed before saving the device state.
> 
> v2: add comments to the changes

...

> 
> Signed-off-by: Rajvi Jingar <rajvi.jingar@...el.com>
> Suggested-by: David E. Box <david.e.box@...ux.intel.com>
> ---

Patch changelogs aren't kept in the commit message. Place them here after the
"---" line. In this location, it won't affect applying the patch.

David

>  drivers/pci/pci-driver.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 588588cfda48..ffe76f238d7e 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -834,20 +834,14 @@ static int pci_pm_suspend_noirq(struct device *dev)
>  		}
>  	}
>  
> -	if (pci_dev->skip_bus_pm) {
> +	if (!pci_dev->state_saved) {
> +		pci_save_state(pci_dev);
>  		/*
> -		 * Either the device is a bridge with a child in D0 below it, or
> -		 * the function is running for the second time in a row without
> -		 * going through full resume, which is possible only during
> -		 * suspend-to-idle in a spurious wakeup case.  The device should
> -		 * be in D0 at this point, but if it is a bridge, it may be
> -		 * necessary to save its state.
> +		 * If the device is a bridge with a child in D0 below it, it
> needs to
> +		 * stay in D0, so check skip_bus_pm to avoid putting it into a
> +		 * low-power state in that case.
>  		 */
> -		if (!pci_dev->state_saved)
> -			pci_save_state(pci_dev);
> -	} else if (!pci_dev->state_saved) {
> -		pci_save_state(pci_dev);
> -		if (pci_power_manageable(pci_dev))
> +		if (!pci_dev->skip_bus_pm && pci_power_manageable(pci_dev))
>  			pci_prepare_to_sleep(pci_dev);
>  	}
>