Re: [PATCH] PCI / PM: Always check PME wakeup capability for runtime wakeup support

[Rafael J. Wysocki]

On Sunday, March 18, 2018 8:12:15 PM CET Kai-Heng Feng wrote:
> USB controller ASM1042 stops working after commit de3ef1eb1cd0 ("PM /
> core: Drop run_wake flag from struct dev_pm_info").
> 
> The device in question is not power managed by platform firmware,
> furthermore, it only supports PME# from D3cold:
> Capabilities: [78] Power Management version 3
>        Flags: PMEClk- DSI- D1- D2- AuxCurrent=55mA PME(D0-,D1-,D2-,D3hot-,D3cold+)
>        Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-

That's somewhat unusual, but OK.

> Before the commit, the device never gets runtime suspended. After the
> commit, the device gets runtime suspended, so it does not respond to any
> PME#.
> 
> usb_hcd_pci_probe() mandatorily calls device_wakeup_enable(), hence
> device_can_wakeup() in pci_dev_run_wake() always returns true.
> 
> So pci_dev_run_wake() needs to check PME wakeup capability as its first
> condition.
> 
> Fixes: de3ef1eb1cd0 ("PM / core: Drop run_wake flag from struct dev_pm_info")
> Cc: stable@xxxxxxxxxxxxxxx # 4.13+
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> ---
>  drivers/pci/pci.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index f6a4dd10d9b0..e026d8f313ec 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2125,16 +2125,13 @@ bool pci_dev_run_wake(struct pci_dev *dev)
>  {
>  	struct pci_bus *bus = dev->bus;
>  
> -	if (device_can_wakeup(&dev->dev))
> -		return true;
> -
> -	if (!dev->pme_support)
> -		return false;

Why are you removing this check?

> -
>  	/* PME-capable in principle, but not from the target power state */
> -	if (!pci_pme_capable(dev, pci_target_state(dev, false)))
> +	if (!pci_pme_capable(dev, pci_target_state(dev, true)))
>  		return false;
>  
> +	if (device_can_wakeup(&dev->dev))
> +		return true;
> +
>  	while (bus->parent) {
>  		struct pci_dev *bridge = bus->self;
>  
> 

Thanks,
Rafael