Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 於 2018年9月20日 週四 下午10:43寫道： > > On Thu, 20 Sep 2018, AceLan Kao wrote: > > > We found a S5 current leakage issue on Dell DW1820 WiFi/BT combo card > > which uses Qualcomm QCA6174 SoC. It also comes with WiFi and BT failure > > when encountered current leakage issue. > > 1. Power on, both WiFi and BT work. > > 2. Power off and found a current leakage issue(consumes ~0.5W) > > 3. Power on, no WiFi and BT devices can be found in lspci and lsusb. > > 4. Power off, there is no current leakage issue at S5. > > 5. continue to 1. > > > > From Qualcomm's report: > > Based on the USB sniffer log, the difference between Linux and Windows > > is USB LPM setting(no LPM transaction on Windows) which may leads to > > the voltage leakage on Linux S5 state. > > > > After checked the LPM related code and found, when system is going to > > enter S5, it resumes the USB devices from runtime suspend and enables > > USB2 LPM, and then it calls usb_dev_poweroff() -> usb_suspend(), and > > leave USB2 LPM stays enabled. > > But usb_suspend() -> usb_suspend_both() -> usb_suspend_device() -> > generic_suspend() -> usb_port_suspend() -> > usb_set_usb2_hardware_lpm(udev, 0). So why does USB2 LPM stay enabled? Right, after checking the normal case, it calls usb_set_usb2_hardware_lpm(udev, 0) eventually. In the buggy machine, it doesn't reach that part and stops somewhere after resume. But unfortunately, I can't duplicate the issue after doing some experiments anymore, so I can't get more info about that. I'll dig further and get back to you when I have any progress. > > > Disable USB2 LPM in usb_suspend() fixes the issue mentioned above, > > and try 30 times of s2idle, S3 and S5, the USB devices keep working > > well. Disable USB2 LPM seems do no harm to the system. > > > > Signed-off-by: AceLan Kao <acelan.kao@xxxxxxxxxxxxx> > > --- > > drivers/usb/core/driver.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c > > index e76e95f62f76..ac5e60d7104f 100644 > > --- a/drivers/usb/core/driver.c > > +++ b/drivers/usb/core/driver.c > > @@ -1463,6 +1463,9 @@ int usb_suspend(struct device *dev, pm_message_t msg) > > struct usb_device *udev = to_usb_device(dev); > > int r; > > > > + if (udev->usb2_hw_lpm_enabled == 1) > > + usb_set_usb2_hardware_lpm(udev, 0); > > At this point the device may still be in runtime suspend. Is that > really okay? > > Alan Stern > > > + > > unbind_no_pm_drivers_interfaces(udev); > > > > /* From now on we are sure all drivers support suspend/resume > > >
