> On Oct 30, 2018, at 23:00, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, 30 Oct 2018, Mathias Nyman wrote:
>
>> On 30.10.2018 07:54, Kai-Heng Feng wrote:
>>> USB Bluetooth controller QCA ROME (0cf3:e007) sometimes stops working
>>> after S3:
>>> [ 165.110742] Bluetooth: hci0: using NVM file: qca/nvm_usb_00000302.bin
>>> [ 168.432065] Bluetooth: hci0: Failed to send body at 4 of 1953 (-110)
>>>
>>> After some experiments, I found that disabling LPM can workaround the
>>> issue.
>>>
>>> On some platforms, the USB power is cut during S3, so the driver uses
>>> reset-resume to resume the device. During port resume, LPM gets enabled
>>> twice, by usb_reset_and_verify_device() and usb_port_resume().
>>>
>>> So let's enable LPM for just once, as this solves the issue for the
>>> device in question.
>>>
>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
>>> ---
>>> drivers/usb/core/driver.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
>>> index 53564386ed57..e11d2eac76b6 100644
>>> --- a/drivers/usb/core/driver.c
>>> +++ b/drivers/usb/core/driver.c
>>> @@ -1901,7 +1901,8 @@ int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable)
>>> struct usb_hcd *hcd = bus_to_hcd(udev->bus);
>>> int ret = -EPERM;
>>>
>>> - if (enable && !udev->usb2_hw_lpm_allowed)
>>> + if (enable && !udev->usb2_hw_lpm_allowed ||
>>> + udev->usb2_hw_lpm_enabled == enable)
>>> return 0;
>>>
>>> if (hcd->driver->set_usb2_hw_lpm) {
>>>
>>
>> Something like that would probably work.
>>
>> Would it make sense to skip USB2 hw LPM enabling in usb_port_resume() if
>> port was just reset (and thus LPM enabled)?
>>
>> something like this:
>>
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -3520,7 +3520,7 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>> hub_port_logical_disconnect(hub, port1);
>> } else {
>> /* Try to enable USB2 hardware LPM */
>> - if (udev->usb2_hw_lpm_capable == 1)
>> + if (udev->usb2_hw_lpm_capable == 1 && !udev->reset_resume)
>> usb_set_usb2_hardware_lpm(udev, 1);
>>
>> /* Try to enable USB3 LTM */
>
> Why not simply test whether udev->usb2_hw_lpm_enabled is already true?
>
> if (udev->usb2_hw_lpm_capable == 1 &&
> !udev->usb2_hw_lpm_enabled)
>
> Or even put this extra test into usb_set_usb2_hardware_lpm().
I think it makes sense to merge all checks into usb_set_usb2_hardware_lpm().
I’ll resend one with this suggestion.
Kai-Heng
>
> Alan Stern
