m68k: mvme147: Reinstate early console

Commit a38eaa0 ("m68k/mvme147: config.c - Remove unused
functions"), removed the console functionality for the mvme147 instead
of wiring it up to an early console.  Put the console write function
back and wire it up like mvme16x does so it's possible to see Linux boot
on this fine hardware once more.

Fixes: a38eaa0 ("m68k/mvme147: config.c - Remove unused functions")
Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Co-developed-by: Finn Thain <fthain@linux-m68k.org>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/a82e8f0068a8722996a0ccfe666abb5e0a5c120d.1730850684.git.fthain@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Author: fifteenhex

arch/m68k/kernel/early_printk.c

@@ -13,6 +13,7 @@
 #include <asm/setup.h>
 
 
+#include "../mvme147/mvme147.h"
 #include "../mvme16x/mvme16x.h"
 
 asmlinkage void __init debug_cons_nputs(const char *s, unsigned n);
@@ -22,7 +23,9 @@ static void __ref debug_cons_write(struct console *c,
 {
 #if !(defined(CONFIG_SUN3) || defined(CONFIG_M68000) || \
       defined(CONFIG_COLDFIRE))
-	if (MACH_IS_MVME16x)
+	if (MACH_IS_MVME147)
+		mvme147_scc_write(c, s, n);
+	else if (MACH_IS_MVME16x)
 		mvme16x_cons_write(c, s, n);
 	else
 		debug_cons_nputs(s, n);

arch/m68k/mvme147/config.c

@@ -32,6 +32,7 @@
 #include <asm/mvme147hw.h>
 #include <asm/config.h>
 
+#include "mvme147.h"
 
 static void mvme147_get_model(char *model);
 static void __init mvme147_sched_init(void);
@@ -185,3 +186,32 @@ int mvme147_hwclk(int op, struct rtc_time *t)
 	}
 	return 0;
 }
+
+static void scc_delay(void)
+{
+	__asm__ __volatile__ ("nop; nop;");
+}
+
+static void scc_write(char ch)
+{
+	do {
+		scc_delay();
+	} while (!(in_8(M147_SCC_A_ADDR) & BIT(2)));
+	scc_delay();
+	out_8(M147_SCC_A_ADDR, 8);
+	scc_delay();
+	out_8(M147_SCC_A_ADDR, ch);
+}
+
+void mvme147_scc_write(struct console *co, const char *str, unsigned int count)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	while (count--)	{
+		if (*str == '\n')
+			scc_write('\r');
+		scc_write(*str++);
+	}
+	local_irq_restore(flags);
+}

arch/m68k/mvme147/mvme147.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct console;
+
+/* config.c */
+void mvme147_scc_write(struct console *co, const char *str, unsigned int count);