m68k/mac: Make SCC reset work more reliably
For SCC initialization we cannot assume that the control register is in
the correct state to accept a register pointer. So first read from the
control register in order to "sync" up.
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/kernel/head.S b/arch/m68k/kernel/head.S
index 7d7913f..4c99bab 100644
--- a/arch/m68k/kernel/head.S
+++ b/arch/m68k/kernel/head.S
@@ -2915,7 +2915,9 @@
#if defined(MAC_USE_SCC_A) || defined(MAC_USE_SCC_B)
movel %pc@(L(mac_sccbase)),%a0
- /* Reset SCC device */
+ /* Reset SCC register pointer */
+ moveb %a0@(mac_scc_cha_a_ctrl_offset),%d0
+ /* Reset SCC device: write register pointer then register value */
moveb #9,%a0@(mac_scc_cha_a_ctrl_offset)
moveb #0xc0,%a0@(mac_scc_cha_a_ctrl_offset)
/* Wait for 5 PCLK cycles, which is about 68 CPU cycles */