Fix existence check for MMIO-mapped 16550 UARTs

Changeset 982e6fce0e47 added an existence test for UARTs.
Unfortunately, the existence test happens before MMIO UARTs are
ioremapped, therefore it may not be probing where it thinks it's
probing.  Rather than moving more code around, I think it's probably
safe to assume the arch code knows what it's doing if it passes in an
MMIO UART.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 6d5f90638bda128d2c33e65c8605aa07a8407ff6..1f889070083d5443e481bc86d30b60354c407319 100644 (file)
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -302,6 +302,13 @@ static int check_existence(struct ns16550 *uart)
 {
     unsigned char status, scratch, scratch2, scratch3;
 
+    /*
+     * We can't poke MMIO UARTs until they get I/O remapped later. Assume that
+     * if we're getting MMIO UARTs, the arch code knows what it's doing.
+     */
+    if ( uart->io_base >= 0x10000 )
+        return 1;
+
     /*
      * Do a simple existence test first; if we fail this,
      * there's no point trying anything else.