linux-kernel - Re: [PATCH v4] PCI / PM: Always check PME wakeup capability for runtime wakeup support

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Message-ID: <20180507214817.GC133147@bhelgaas-glaptop.roam.corp.google.com>
Date:   Mon, 7 May 2018 16:48:17 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     bhelgaas@...gle.com, rafael.j.wysocki@...el.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] PCI / PM: Always check PME wakeup capability for
 runtime wakeup support

On Mon, May 07, 2018 at 02:11:20PM +0800, 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-
> 
> Before commit de3ef1eb1cd0, the device never gets runtime suspended.
> After that commit, the device gets runtime suspended to D3hot, which can
> not generate any PME#.
> 
> usb_hcd_pci_probe() unconditionally 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.
> 
> In addition, change wakeup flag passed to pci_target_state() from false
> to true, because we want to find the deepest state that the device can
> still generate PME#. In this case, it's D0 for the device in question.
> 
> Fixes: de3ef1eb1cd0 ("PM / core: Drop run_wake flag from struct dev_pm_info")
> Cc: stable@...r.kernel.org # 4.13+
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

Rafael, can you queue this up?  de3ef1eb1cd0 went through your tree,
and I don't really understand the patch, so I'll rely on your review.

> ---
> v4: Correct some errors in commit log.
> 
> v3: State the reason why the wakeup flag gets changed.
> 
> v2: Explicitly check dev->pme_support.
> 
>  drivers/pci/pci.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index a04197ce767d..c2616cad3a1d 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2138,16 +2138,16 @@ 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;
>  
>  	/* 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;
>  
> -- 
> 2.17.0
>