[PATCH] hw/char/escc: Implement loopback mode

[Thomas Huth <huth@tuxfamily.org>]

The firmware of the m68k next-cube machine uses the loopback mode
for self-testing the hardware and currently fails during this step.
By implementing the loopback mode, we can make the firmware pass
to the next step.

Signed-off-by: Thomas Huth <huth@tuxfamily.org>
---
 hw/char/escc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/char/escc.c b/hw/char/escc.c
index 4f3872bfe9..4be66053c1 100644
--- a/hw/char/escc.c
+++ b/hw/char/escc.c
@@ -653,7 +653,9 @@ static void escc_mem_write(void *opaque, hwaddr addr,
         escc_update_irq(s);
         s->tx = val;
         if (s->wregs[W_TXCTRL2] & TXCTRL2_TXEN) { /* tx enabled */
-            if (qemu_chr_fe_backend_connected(&s->chr)) {
+            if (s->wregs[W_MISC2] & MISC2_LCL_LOOP) {
+                serial_receive_byte(s, s->tx);
+            } else if (qemu_chr_fe_backend_connected(&s->chr)) {
                 /*
                  * XXX this blocks entire thread. Rewrite to use
                  * qemu_chr_fe_write and background I/O callbacks
-- 
2.41.0