linux-kernel - Re: [PATCH v3] PCI / PM: Always check PME wakeup capability for runtime wakeup support

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Message-Id: <798A7C7A-A3DA-4C0E-A774-48042430EE1A@canonical.com>
Date:   Fri, 13 Apr 2018 14:58:11 +0800
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     bhelgaas@...gle.com
Cc:     rafael.j.wysocki@...el.com, linux-pci@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] PCI / PM: Always check PME wakeup capability for
 runtime wakeup support

Hi Bjorn and Rafael,

> On Apr 1, 2018, at 12:40 AM, Kai-Heng Feng <kai.heng.feng@...onical.com>  
> 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, 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.
>
> 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#.
>
> 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>
> ---
> v3: State the reason why the wakeup flag gets changed.
>
> v2: Explicitly check dev->pme_support.

If this patch is good enough, I am hoping it can get merged in v4.17.

Kai-Heng

>
>  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 f6a4dd10d9b0..52821a21fc07 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2125,16 +2125,16 @@ 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;
>
> -- 
> 2.15.1