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

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Date:   Mon, 12 Jun 2017 18:12:42 +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 Mon, Jun 12, 2017 at 3:04 PM, Kai-Heng Feng
<kai.heng.feng@...onical.com> wrote:
> 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:
>>
>> 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.

Put the device into D2 instead of D3 can make the wakeup signaling
work, i.e. USB devices can be correctly detected after plugged into
EHCI port.

Do you think this alternative an acceptable workaround?

>
> Thanks for the review.
>