[PATCH v1 1/2] usb: xhci: Skip xhci_reset in xhci_resume if xhci is being removed

[Roy Luo <royluo@google.com>]

xhci_reset() currently returns -ENODEV if XHCI_STATE_REMOVING is
set, without completing the xhci handshake, unless the reset completes
exceptionally quickly. This behavior causes a regression on Synopsys
DWC3 USB controllers with dual-role capabilities.

Specifically, when a DWC3 controller exits host mode and removes xhci
while a reset is still in progress, and then attempts to configure its
hardware for device mode, the ongoing, incomplete reset leads to
critical register access issues. All register reads return zero, not
just within the xHCI register space (which might be expected during a
reset), but across the entire DWC3 IP block.

This patch addresses the issue by preventing xhci_reset() from being
called in xhci_resume() and bailing out early in the reinit flow when
XHCI_STATE_REMOVING is set.

Cc: stable@vger.kernel.org
Fixes: 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state() helper")
Suggested-by: Mathias Nyman <mathias.nyman@intel.com>
Signed-off-by: Roy Luo <royluo@google.com>
---
 drivers/usb/host/xhci.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 90eb491267b5..244b12eafd95 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1084,7 +1084,10 @@ int xhci_resume(struct xhci_hcd *xhci, bool power_lost, bool is_auto_resume)
 		xhci_dbg(xhci, "Stop HCD\n");
 		xhci_halt(xhci);
 		xhci_zero_64b_regs(xhci);
-		retval = xhci_reset(xhci, XHCI_RESET_LONG_USEC);
+		if (xhci->xhc_state & XHCI_STATE_REMOVING)
+			retval = -ENODEV;
+		else
+			retval = xhci_reset(xhci, XHCI_RESET_LONG_USEC);
 		spin_unlock_irq(&xhci->lock);
 		if (retval)
 			return retval;
-- 
2.49.0.1204.g71687c7c1d-goog