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? > 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 >
