Drain FIFOs on init same as com(4) does it and reduce the RX FIFO interrupt

trigger to 1 character.  This fixes a hang seen on the allwinner,sun5i-r8
board during boot when the driver switches to interrupts and no terminal
is attached.

ok kettenis

diff --git a/sys/arch/armv7/sunxi/sxiuart.c b/sys/arch/armv7/sunxi/sxiuart.c
index 269af78..8944ee1 100644 (file)
--- a/sys/arch/armv7/sunxi/sxiuart.c
+++ b/sys/arch/armv7/sunxi/sxiuart.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sxiuart.c,v 1.12 2016/08/12 16:09:37 kettenis Exp $   */
+/*     $OpenBSD: sxiuart.c,v 1.13 2016/08/15 04:32:57 mglocker Exp $   */
 /*
  * Copyright (c) 2005 Dale Rahn <drahn@motorola.com>
  * Copyright (c) 2013 Artturi Alm
@@ -660,11 +660,18 @@ sxiuartopen(dev_t dev, int flag, int mode, struct proc *p)
                iot = sc->sc_iot;
                ioh = sc->sc_ioh;
 
-               bus_space_write_1(iot, ioh, SXIUART_FCR, FIFOE | FIFO_RXT2);
-               delay(100);
-               while (ISSET(bus_space_read_1(iot, ioh, SXIUART_LSR),
-                   LSR_RXRDY))
+               /* (Re)enable and drain FIFOs. */
+               for (;;) {
+                       bus_space_write_1(iot, ioh, SXIUART_FCR, 0);
+                       delay(100);
                        (void)bus_space_read_1(iot, ioh, SXIUART_RBR);
+                       bus_space_write_1(iot, ioh, SXIUART_FCR,
+                           FIFOE | FIFO_RXT0);
+                       delay(100);
+                       if (!ISSET(bus_space_read_1(iot, ioh, SXIUART_LSR),
+                           LSR_RXRDY))
+                               break;
+               }
 
                sc->sc_mcr = MCR_DTR | MCR_RTS | MCR_IENABLE;
                bus_space_write_1(iot, ioh, SXIUART_MCR, sc->sc_mcr);