MIPS: Alchemy: Make 32kHz and r4k timer coexist peacefully

Now that the r4k timer is registered no matter what, bump the rating of
the Alchemy 32kHz timer so that it gets used when it is working,
and fall back on the r4k when it isn't.

This fixes a timer-related hang on platform with a working 32kHz timer
(the better rated c0 timer stops while executing 'wait' leading to (almost)
eternal sleep) and an oops on boot on platforms without a working 32kHz
timer (due to double registration of the r4k timer).

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc:  Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/4728/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/alchemy/common/time.c

@@ -53,7 +53,7 @@ static struct clocksource au1x_counter1_clocksource = {
 	.read		= au1x_counter1_read,
 	.mask		= CLOCKSOURCE_MASK(32),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-	.rating		= 100,
+	.rating		= 1500,
 };
 
 static int au1x_rtcmatch2_set_next_event(unsigned long delta,
@@ -84,7 +84,7 @@ static irqreturn_t au1x_rtcmatch2_irq(int irq, void *dev_id)
 static struct clock_event_device au1x_rtcmatch2_clockdev = {
 	.name		= "rtcmatch2",
 	.features	= CLOCK_EVT_FEAT_ONESHOT,
-	.rating		= 100,
+	.rating		= 1500,
 	.set_next_event	= au1x_rtcmatch2_set_next_event,
 	.set_mode	= au1x_rtcmatch2_set_mode,
 	.cpumask	= cpu_all_mask,
@@ -158,20 +158,6 @@ cntr_err:
 	return -1;
 }
 
-static void __init alchemy_setup_c0timer(void)
-{
-	/*
-	 * MIPS kernel assigns 'au1k_wait' to 'cpu_wait' before this
-	 * function is called.  Because the Alchemy counters are unusable
-	 * the C0 timekeeping code is installed and use of the 'wait'
-	 * instruction must be prohibited, which is done most easily by
-	 * assigning NULL to cpu_wait.
-	 */
-	cpu_wait = NULL;
-	r4k_clockevent_init();
-	init_r4k_clocksource();
-}
-
 static int alchemy_m2inttab[] __initdata = {
 	AU1000_RTC_MATCH2_INT,
 	AU1500_RTC_MATCH2_INT,
@@ -186,8 +172,7 @@ void __init plat_time_init(void)
 	int t;
 
 	t = alchemy_get_cputype();
-	if (t == ALCHEMY_CPU_UNKNOWN)
-		alchemy_setup_c0timer();
-	else if (alchemy_time_init(alchemy_m2inttab[t]))
-		alchemy_setup_c0timer();
+	if (t == ALCHEMY_CPU_UNKNOWN ||
+	    alchemy_time_init(alchemy_m2inttab[t]))
+		cpu_wait = NULL;	/* wait doesn't work with r4k timer */
 }