linux-kernel - Re: [PATCH] usb: host: ehci: workaround PME bug on AMD EHCI controller

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Date:   Mon, 12 Jun 2017 15:04:40 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: host: ehci: workaround PME bug on AMD EHCI controller

On Fri, Jun 9, 2017 at 10:43 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Fri, 9 Jun 2017, Kai-Heng Feng wrote:
>
>> As Alan Stern points out [1], the PME signal is not enabled when
>> controller is in D3, therefore it's not being woken up when new deivces
>> get plugged in.
>>
>> Workaround this bug by preventing the controller enters D3 power state.
>>
>> [1] https://www.spinics.net/lists/linux-usb/msg157462.html
>>
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>> ---
>>  drivers/usb/host/ehci-pci.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
>> index 93326974ff4b..616685f83954 100644
>> --- a/drivers/usb/host/ehci-pci.c
>> +++ b/drivers/usb/host/ehci-pci.c
>> @@ -181,6 +181,8 @@ static int ehci_pci_setup(struct usb_hcd *hcd)
>>               if (pdev->device == 0x7808) {
>>                       ehci->use_dummy_qh = 1;
>>                       ehci_info(ehci, "applying AMD SB700/SB800/Hudson-2/3 EHCI dummy qh workaround\n");
>> +
>> +                     pdev->dev_flags |= PCI_DEV_FLAGS_NO_D3;
>>               }
>>               break;
>>       case PCI_VENDOR_ID_VIA:
>
> Is this really the right solution?  Maybe it would be better to allow
> the controller to go into D3 provided no wakeup signal is needed.  You
> could do:
>
>                 device_set_wakeup_capable(&pdev->dev, 0);

This doesn't work.
After applying this function, still nothing happens when devices get plugged in.
IIUC this function disable the wakeup function, but what I want to do
here is to have PME signal works even when runtime PM is enabled.

I also saw some legacy PCI PM stuff, so I also tried:
device_set_wakeup_capable(&pdev->dev, 1);
...doesn't work either.

>
> Another alternative is to put the controller into D2 instead of D3, but
> (1) I don't know how to do that, and (2) we don't know if wakeup
> signalling works any better in D2 than it does in D3.

I'll try if D2 works.

Thanks for the review.

>
> Alan Stern
>