usb: typec: altmodes/displayport: Fall back to multi-func pins

If our port-partner supports both DP-only operation (pin-assignment C)
and multi-func operation (pin-assignment D) and we only support
pin-assignment D and the port-partner prefers DP-only mode, then
before this commit we would and up masking out pin-assignment D from
the available pin-assignments and fail to pick a pin-assignment.

Instead only mask out the multi-func pin-assignments if we support
dp-only pin-assignments, so that we correctly fall-back to a multi-func
pin-assignment in this case (by picking pin-assignment D).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 610d790..1b2afeb 100644 (file)
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -100,7 +100,7 @@ static int dp_altmode_configure(struct dp_altmode *dp, u8 con)
                if (dp->data.status & DP_STATUS_PREFER_MULTI_FUNC &&
                    pin_assign & DP_PIN_ASSIGN_MULTI_FUNC_MASK)
                        pin_assign &= DP_PIN_ASSIGN_MULTI_FUNC_MASK;
-               else
+               else if (pin_assign & DP_PIN_ASSIGN_DP_ONLY_MASK)
                        pin_assign &= DP_PIN_ASSIGN_DP_ONLY_MASK;
 
                if (!pin_assign)