linux-kernel - Re: [PATCH v2] PCI / PM: Always check PME wakeup capability for runtime wakeup support

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Message-Id: <44B8B950-4C07-447E-9F12-AD60C536150F@canonical.com>
Date:   Fri, 30 Mar 2018 17:30:10 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     linux-pci@...r.kernel.org, bhelgaas@...gle.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] PCI / PM: Always check PME wakeup capability for
 runtime wakeup support

Rafael J. Wysocki <rjw@...ysocki.net> wrote:

> On Monday, March 26, 2018 7:54:35 AM CEST Kai Heng Feng wrote:
>> Hi Bjorn, Rafael,
>>
>>> On Mar 19, 2018, at 10:09 PM, 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.
>>>
>>> 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>
>>
>>
>> Is there any improvement I can address?
>> Or do you have any concern about this patch?
>>
>> Kai-Heng
>>
>>> ---
>>> 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 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)))
>
> So why do you change 'false' to 'true' here?
>
> At least that change should be mentioned in the changelog too.

I'll update the reason in the change log.

Thanks.

>
>>> return false;
>>>
>>> +	if (device_can_wakeup(&dev->dev))
>>> +		return true;
>>> +
>>>  	while (bus->parent) {
>>>  		struct pci_dev *bridge = bus->self;