usb: dwc2: optionally assert phy reset when waking up

On the rk3288 USB host-only port (the one that's not the OTG-enabled
port) the PHY can get into a bad state when a wakeup is asserted (not
just a wakeup from full system suspend but also a wakeup from
autosuspend).

We can get the PHY out of its bad state by asserting its "port reset",
but unfortunately that seems to assert a reset onto the USB bus so it
could confuse things if we don't actually deenumerate / reenumerate the
device.

We can also get the PHY out of its bad state by fully resetting it using
the reset from the CRU (clock reset unit), which does a more full
reset.  The CRU-based reset appears to actually cause devices on the bus
to be removed and reinserted, which fixes the problem (albeit in a hacky
way).

It's unfortunate that we need to do a full re-enumeration of devices at
wakeup time, but this is better than alternative of letting the bus get
wedged.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yunzhi Li <lyz@rock-chips.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
index 9aa9682a5cd2..c01fa8ffc0c8 100644
--- a/drivers/usb/dwc2/platform.c
+++ b/drivers/usb/dwc2/platform.c
@@ -481,6 +481,15 @@ static int dwc2_driver_probe(struct platform_device *dev)
                 hsotg->gadget_enabled = 1;
         }
 
+        hsotg->reset_phy_on_wake =
+                of_property_read_bool(dev->dev.of_node,
+                                      "snps,reset-phy-on-wake");
+        if (hsotg->reset_phy_on_wake && !hsotg->phy) {
+                dev_warn(hsotg->dev,
+                         "Quirk reset-phy-on-wake only supports generic PHYs\n");
+                hsotg->reset_phy_on_wake = false;
+        }
+
         if (hsotg->dr_mode != USB_DR_MODE_PERIPHERAL) {
                 retval = dwc2_hcd_init(hsotg);
                 if (retval) {