[PATCH 18/22] usb: xhci: improve xhci_port_missing_cas_quirk()

[Niklas Neronin <niklas.neronin@linux.intel.com>]

Previously the function dropped all RW1CS and Wake bits and set the
Warm Port Reset (WPR) bit.

This was done by manually clearing RW1CS and Wake bits and then
setting WPR. Instead, use xhci_port_state_to_neutral(), which
already drops all bits with write side effects (e.g. RW1CS, RW1S and
reserved-zero fields), and produces a safe value for writeback.

Afterwards, explicitly clear the Wake bits.

Compared to the previous logic, this also correctly clears additional
bits such as reserved-zero (bits 2, 28, 29) and RW1S bit (bit 4),
which could otherwise lead to unintended behavior.

Overall this simplifies the code and aligns it with the generic PORTSC
sanitization logic.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
---
 drivers/usb/host/xhci-hub.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 0375929aac70..17347bca0682 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -1785,8 +1785,9 @@ static bool xhci_port_missing_cas_quirk(struct xhci_port *port)
 	if (pls != PLS_POLLING && pls != PLS_COMP_MODE)
 		return false;
 
-	/* clear wakeup/change bits, and do a warm port reset */
-	portsc &= ~(PORTSC_RW1CS_BITS | PORT_WAKE_BITS);
+	portsc = xhci_port_state_to_neutral(portsc);
+	/* clear wakeup and do a warm port reset */
+	portsc &= ~PORT_WAKE_BITS;
 	portsc |= PORT_WPR;
 	xhci_portsc_writel(port, portsc);
 	/* flush write */
-- 
2.50.1