m68k/mac: Fix unexpected interrupt with CONFIG_EARLY_PRINTK
The present code does not wait for the SCC to finish resetting itself
before trying to initialise the device. The result is that the SCC
interrupt sources become enabled (if they weren't already). This leads to
an early boot crash (unexpected interrupt) given CONFIG_EARLY_PRINTK. Fix
this by adding a delay. A successful reset disables the interrupt sources.
Also, after the reset for channel A setup, the SCC then gets a second
reset for channel B setup which leaves channel A uninitialised again. Fix
this by performing the reset only once.
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Cc: stable@vger.kernel.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/kernel/head.S b/arch/m68k/kernel/head.S
index d197e7f..ac85f16 100644
--- a/arch/m68k/kernel/head.S
+++ b/arch/m68k/kernel/head.S
@@ -2752,11 +2752,9 @@
#ifdef CONFIG_MAC
L(scc_initable_mac):
- .byte 9,12 /* Reset */
.byte 4,0x44 /* x16, 1 stopbit, no parity */
.byte 3,0xc0 /* receiver: 8 bpc */
.byte 5,0xe2 /* transmitter: 8 bpc, assert dtr/rts */
- .byte 9,0 /* no interrupts */
.byte 10,0 /* NRZ */
.byte 11,0x50 /* use baud rate generator */
.byte 12,1,13,0 /* 38400 baud */
@@ -2899,6 +2897,7 @@
is_not_mac(L(serial_init_not_mac))
#ifdef SERIAL_DEBUG
+
/* You may define either or both of these. */
#define MAC_USE_SCC_A /* Modem port */
#define MAC_USE_SCC_B /* Printer port */
@@ -2908,9 +2907,21 @@
#define mac_scc_cha_b_data_offset 0x4
#define mac_scc_cha_a_data_offset 0x6
+#if defined(MAC_USE_SCC_A) || defined(MAC_USE_SCC_B)
+ movel %pc@(L(mac_sccbase)),%a0
+ /* Reset SCC device */
+ 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 */
+ /* 5 / 3.6864 MHz = approx. 1.36 us = 68 / 50 MHz */
+ movel #35,%d0
+5:
+ subq #1,%d0
+ jne 5b
+#endif
+
#ifdef MAC_USE_SCC_A
/* Initialize channel A */
- movel %pc@(L(mac_sccbase)),%a0
lea %pc@(L(scc_initable_mac)),%a1
5: moveb %a1@+,%d0
jmi 6f
@@ -2922,9 +2933,6 @@
#ifdef MAC_USE_SCC_B
/* Initialize channel B */
-#ifndef MAC_USE_SCC_A /* Load mac_sccbase only if needed */
- movel %pc@(L(mac_sccbase)),%a0
-#endif /* MAC_USE_SCC_A */
lea %pc@(L(scc_initable_mac)),%a1
7: moveb %a1@+,%d0
jmi 8f
@@ -2933,6 +2941,7 @@
jra 7b
8:
#endif /* MAC_USE_SCC_B */
+
#endif /* SERIAL_DEBUG */
jra L(serial_init_done)
@@ -3006,17 +3015,17 @@
#ifdef SERIAL_DEBUG
-#ifdef MAC_USE_SCC_A
+#if defined(MAC_USE_SCC_A) || defined(MAC_USE_SCC_B)
movel %pc@(L(mac_sccbase)),%a1
+#endif
+
+#ifdef MAC_USE_SCC_A
3: btst #2,%a1@(mac_scc_cha_a_ctrl_offset)
jeq 3b
moveb %d0,%a1@(mac_scc_cha_a_data_offset)
#endif /* MAC_USE_SCC_A */
#ifdef MAC_USE_SCC_B
-#ifndef MAC_USE_SCC_A /* Load mac_sccbase only if needed */
- movel %pc@(L(mac_sccbase)),%a1
-#endif /* MAC_USE_SCC_A */
4: btst #2,%a1@(mac_scc_cha_b_ctrl_offset)
jeq 4b
moveb %d0,%a1@(mac_scc_cha_b_data_offset)