On Fri, May 06, 2022 at 02:18:06PM -0400, Alan Stern wrote:
> [CC: list drastically reduced]
>
> On Fri, May 06, 2022 at 09:51:46AM -0700, Matthias Kaehlcke wrote:
> > I found this, as I commented on the other thread:
> >
> > commit c4a5153e87fdf6805f63ff57556260e2554155a5
> > Author: Manu Gautam <mgautam@xxxxxxxxxxxxxx>
> > Date: Thu Jan 18 16:54:30 2018 +0530
> >
> > usb: dwc3: core: Power-off core/PHYs on system_suspend in host mode
> >
> > Commit 689bf72c6e0d ("usb: dwc3: Don't reinitialize core during
> > host bus-suspend/resume") updated suspend/resume routines to not
> > power_off and reinit PHYs/core for host mode.
> > It broke platforms that rely on DWC3 core to power_off PHYs to
> > enter low power state on system suspend.
> >
> > Perform dwc3_core_exit/init only during host mode system_suspend/
> > resume to addresses power regression from above mentioned patch
> > and also allow USB session to stay connected across
> > runtime_suspend/resume in host mode. While at it also replace
> > existing checks for HOST only dr_mode with current_dr_role to
> > have similar core driver behavior for both Host-only and DRD+Host
> > configurations.
> >
> > Fixes: 689bf72c6e0d ("usb: dwc3: Don't reinitialize core during host bus-suspend/resume")
> > Reviewed-by: Roger Quadros <rogerq@xxxxxx>
> > Signed-off-by: Manu Gautam <mgautam@xxxxxxxxxxxxxx>
> > Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> >
> >
> > So apparently powering off the core and PHYs is needed on some
> > platforms.
> >
> > Let's move forward with the core/PHYs off for now and try to
> > come up with a solution (e.g. a DT property that indicates
> > that the core/PHYs can remain powererd) in a separate
> > patch/series.
>
> Isn't it true that if you power off the PHY, the controller will be
> unable to detect resume requests from attached devices? Similarly, won't
> the controller will be unable to detect plug and unplug events on the
> root hub?
>
> Doesn't this mean that if wakeup is enabled on the root hub or any of
> the devices downstream from a root-hub port, the port's PHY must remain
> powered during suspend?
Yes.
Currently the core/PHYs are always powered off during suspend in host mode:
static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
{
...
switch (dwc->current_dr_role) {
case DWC3_GCTL_PRTCAP_HOST:
if (!PMSG_IS_AUTO(msg)) {
dwc3_core_exit(dwc);
break;
}
...
}
With that I would expect wakeup to be broken for all dwc3. I'm a bit confused
though, since dwc3-imx8mp.c seems to support wakeup and the driver landed
after the above patch ...
This series intends to change the above code to something like this:
if (!PMSG_IS_AUTO(msg)) {
if (device_may_wakeup(dwc->dev) &&
device_wakeup_path(dwc->dev)) {
dwc->phy_power_off = false;
} else {
dwc->phy_power_off = true;
dwc3_core_exit(dwc);
}
}
i.e. the core/PHYs would only be powered down if wakeup is disabled or no
wakeup capable devices are connected. With that plug/unplug events still
wouldn't be detected.
