On Sat, Dec 19, 2020 at 12:42:34AM +0800, JC Kuo wrote: > Occasionally, we are seeing some SuperSpeed devices resumes right after > being directed to U3. This commits add 500us delay to ensure LFPS > detector is disabled before sending ACK to firmware. > > [ 16.099363] tegra-xusb 70090000.usb: entering ELPG > [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 > [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 > [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed > > Signed-off-by: JC Kuo <jckuo@xxxxxxxxxx> > --- > drivers/usb/host/xhci-tegra.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c > index 934be1686352..20cdc11f7dc6 100644 > --- a/drivers/usb/host/xhci-tegra.c > +++ b/drivers/usb/host/xhci-tegra.c > @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, > enable); > if (err < 0) > break; > + > + /* > + * wait 500us for LFPS detector to be disabled before sending ACK > + */ > + if (!enable) > + usleep_range(500, 1000); Where does the magic 500us come from? How can we "know" this is long enough? thanks, greg k-h
