usb: dwc3: workaround: unexpected transtion U3 -> RESUME

In DWC3 versions < 2.50a configured without
Hibernation mode enabled, there will be an
extra link status change interrupt if device
detects host-initiated U3 exit.

In that case, core will generate an unnecessary
U3 -> RESUME transition which should be ignored
by the driver.

Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 4ffec1aa2e25..8e53acc0e43e 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2317,6 +2317,34 @@ static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
                 unsigned int evtinfo)
 {
         enum dwc3_link_state    next = evtinfo & DWC3_LINK_STATE_MASK;
+        unsigned int            pwropt;
+
+        /*
+         * WORKAROUND: DWC3 < 2.50a have an issue when configured without
+         * Hibernation mode enabled which would show up when device detects
+         * host-initiated U3 exit.
+         *
+         * In that case, device will generate a Link State Change Interrupt
+         * from U3 to RESUME which is only necessary if Hibernation is
+         * configured in.
+         *
+         * There are no functional changes due to such spurious event and we
+         * just need to ignore it.
+         *
+         * Refers to:
+         *
+         * STAR#9000570034 RTL: SS Resume event generated in non-Hibernation
+         * operational mode
+         */
+        pwropt = DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1);
+        if ((dwc->revision < DWC3_REVISION_250A) &&
+                        (pwropt != DWC3_GHWPARAMS1_EN_PWROPT_HIB)) {
+                if ((dwc->link_state == DWC3_LINK_STATE_U3) &&
+                                (next == DWC3_LINK_STATE_RESUME)) {
+                        dev_vdbg(dwc->dev, "ignoring transition U3 -> Resume\n");
+                        return;
+                }
+        }
 
         /*
          * WORKAROUND: DWC3 Revisions <1.83a have an issue which, depending