6.12-stable review patch. If anyone has any objections, please let me know.
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From: Roy Luo royluo@google.com
commit 3eff494f6e17abf932699483f133a708ac0355dc upstream.
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 stable@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 Link: https://lore.kernel.org/r/20250522190912.457583-2-royluo@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/host/xhci.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -1094,7 +1094,10 @@ int xhci_resume(struct xhci_hcd *xhci, p 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;