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

Alan Stern
2017-06-09T14:43:46Z

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@canonical.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);

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.

Alan Stern