linux-kernel - Re: [PATCH] PCI/PM: Set D3 power state only if the end device supports it.

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Date:   Wed, 31 May 2017 06:43:40 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Geetha sowjanya <gakula@...iumnetworks.com>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, jcm@...hat.com, sgoutham@...ium.com,
        geethasowjanya.akula@...il.com, robert.richter@...ium.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] PCI/PM: Set D3 power state only if the end device
 supports it.

On Wed, 31 May 2017 17:03:32 +0530
Geetha sowjanya <gakula@...iumnetworks.com> wrote:

> Pci driver doesn't check if the device supports D3hot/D3cold power states 
> while setting these power states. The device that doesn't support these 
> states will fail when a driver like vfio try to do D0->D3 power transition.


That's because support for D0 and D3 device states is REQUIRED by the
PCIe spec (Rev 3.1a, 7.6).  Is this yet more non-spec compliance?
Thanks,

Alex

 
> This patch adds a check that allows to set D3 power state only
> for the supported devices.
> 
> Signed-off-by: Geetha sowjanya <gakula@...iumnetworks.com>
> ---
>  drivers/pci/pci.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 563901c..cadd046 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -661,7 +661,8 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
>  
>  	/* check if this device supports the desired state */
>  	if ((state == PCI_D1 && !dev->d1_support)
> -	   || (state == PCI_D2 && !dev->d2_support))
> +	   || (state == PCI_D2 && !dev->d2_support)
> +	   || (state == PCI_D3hot && !pci_pme_capable(dev, state)))
>  		return -EIO;
>  
>  	pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);