usb: typec: mux: intel_pmc_mux: Fix DP alternate mode entry

The PMC needs to be notified separately about HPD (hotplug
detected) signal being high after mode entry. There is a bit
"HPD High" in the Alternate Mode Request that the driver
already sets, but that bit is only valid when the
DisplayPort Alternate Mode is directly entered from
disconnected state.

Fixes: 5c4edcdbcd ("usb: typec: mux: intel: Fix DP_HPD_LVL bit field")
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Tested-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20200529131753.15587-1-heikki.krogerus@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/mux/intel_pmc_mux.c

@@ -148,7 +148,8 @@ pmc_usb_mux_dp_hpd(struct pmc_usb_port *port, struct typec_mux_state *state)
 	msg[0] = PMC_USB_DP_HPD;
 	msg[0] |= port->usb3_port << PMC_USB_MSG_USB3_PORT_SHIFT;
 
-	msg[1] = PMC_USB_DP_HPD_IRQ;
+	if (data->status & DP_STATUS_IRQ_HPD)
+		msg[1] = PMC_USB_DP_HPD_IRQ;
 
 	if (data->status & DP_STATUS_HPD_STATE)
 		msg[1] |= PMC_USB_DP_HPD_LVL;
@@ -161,6 +162,7 @@ pmc_usb_mux_dp(struct pmc_usb_port *port, struct typec_mux_state *state)
 {
 	struct typec_displayport_data *data = state->data;
 	struct altmode_req req = { };
+	int ret;
 
 	if (data->status & DP_STATUS_IRQ_HPD)
 		return pmc_usb_mux_dp_hpd(port, state);
@@ -181,7 +183,14 @@ pmc_usb_mux_dp(struct pmc_usb_port *port, struct typec_mux_state *state)
 	if (data->status & DP_STATUS_HPD_STATE)
 		req.mode_data |= PMC_USB_ALTMODE_HPD_HIGH;
 
-	return pmc_usb_command(port, (void *)&req, sizeof(req));
+	ret = pmc_usb_command(port, (void *)&req, sizeof(req));
+	if (ret)
+		return ret;
+
+	if (data->status & DP_STATUS_HPD_STATE)
+		return pmc_usb_mux_dp_hpd(port, state);
+
+	return 0;
 }
 
 static int