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, 15 insertions, 3 deletions

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 8667ddf3ca74..978232a9e4a8 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -4376,6 +4376,17 @@ static void dwc2_hcd_reset_func(struct work_struct *work)
         spin_unlock_irqrestore(&hsotg->lock, flags);
 }
 
+static void dwc2_hcd_phy_reset_func(struct work_struct *work)
+{
+        struct dwc2_hsotg *hsotg = container_of(work, struct dwc2_hsotg,
+                                                phy_reset_work);
+        int ret;
+
+        ret = phy_reset(hsotg->phy);
+        if (ret)
+                dev_warn(hsotg->dev, "PHY reset failed\n");
+}
+
 /*
  * =========================================================================
  *  Linux HC Driver Functions
@@ -5152,6 +5163,8 @@ static void dwc2_hcd_free(struct dwc2_hsotg *hsotg)
                 destroy_workqueue(hsotg->wq_otg);
         }
 
+        cancel_work_sync(&hsotg->phy_reset_work);
+
         del_timer(&hsotg->wkp_timer);
 }
 
@@ -5293,11 +5306,10 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg)
                 hsotg->hc_ptr_array[i] = channel;
         }
 
-        /* Initialize hsotg start work */
+        /* Initialize work */
         INIT_DELAYED_WORK(&hsotg->start_work, dwc2_hcd_start_func);
-
-        /* Initialize port reset work */
         INIT_DELAYED_WORK(&hsotg->reset_work, dwc2_hcd_reset_func);
+        INIT_WORK(&hsotg->phy_reset_work, dwc2_hcd_phy_reset_func);
 
         /*
          * Allocate space for storing data on status transactions. Normally no