[RFC PATCH v3 05/14] m68k: amiga: Convert to clocksource API

[Finn Thain]

Add a platform clocksource by adapting the existing arch_gettimeoffset
implementation.

Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
Changed since v2:
 - Don't check for timer interrupt in amiga_read_clk() when the timer is
about to be reloaded.

Changed since v1:
 - Moved clk_total access to within the irq lock.
---
 arch/m68k/amiga/config.c | 64 +++++++++++++++++++++++++++-------------
 1 file changed, 43 insertions(+), 21 deletions(-)

diff --git a/arch/m68k/amiga/config.c b/arch/m68k/amiga/config.c
index d4976c1aa0cc..0c2c07318f6c 100644
--- a/arch/m68k/amiga/config.c
+++ b/arch/m68k/amiga/config.c
@@ -17,6 +17,7 @@
 #include <linux/mm.h>
 #include <linux/seq_file.h>
 #include <linux/tty.h>
+#include <linux/clocksource.h>
 #include <linux/console.h>
 #include <linux/rtc.h>
 #include <linux/init.h>
@@ -461,7 +462,28 @@ void __init config_amiga(void)
 		*(unsigned char *)ZTWO_VADDR(0xde0002) |= 0x80;
 }
 
+static u64 amiga_read_clk(struct clocksource *cs);
+
+static struct clocksource amiga_clk = {
+	.name   = "ciab",
+	.rating = 250,
+	.read   = amiga_read_clk,
+	.mask   = CLOCKSOURCE_MASK(32),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
 static unsigned short jiffy_ticks;
+static u32 clk_total;
+
+static irqreturn_t ciab_timer_handler(int irq, void *dev_id)
+{
+	irq_handler_t timer_routine = dev_id;
+
+	clk_total += jiffy_ticks;
+	timer_routine(0, NULL);
+
+	return IRQ_HANDLED;
+}
 
 static void __init amiga_sched_init(irq_handler_t timer_routine)
 {
@@ -481,41 +503,41 @@ static void __init amiga_sched_init(irq_handler_t timer_routine)
 	 * Please don't change this to use ciaa, as it interferes with the
 	 * SCSI code. We'll have to take a look at this later
 	 */
-	if (request_irq(IRQ_AMIGA_CIAB_TA, timer_routine, 0, "timer", NULL))
+	if (request_irq(IRQ_AMIGA_CIAB_TA, ciab_timer_handler, IRQF_TIMER,
+			"timer", timer_routine))
 		pr_err("Couldn't register timer interrupt\n");
 	/* start timer */
 	ciab.cra |= 0x11;
-}
 
-#define TICK_SIZE 10000
+	clocksource_register_hz(&amiga_clk, amiga_eclock);
+}
 
-/* This is always executed with interrupts disabled.  */
-static u32 amiga_gettimeoffset(void)
+static u64 amiga_read_clk(struct clocksource *cs)
 {
-	unsigned short hi, lo, hi2;
+	unsigned long flags;
+	u8 msb, lsb, tmp;
 	u32 ticks, offset = 0;
 
-	/* read CIA B timer A current value */
-	hi  = ciab.tahi;
-	lo  = ciab.talo;
-	hi2 = ciab.tahi;
+	local_irq_save(flags);
 
-	if (hi != hi2) {
-		lo = ciab.talo;
-		hi = hi2;
-	}
-
-	ticks = hi << 8 | lo;
+	/* read CIA B timer A current value */
+	tmp = ciab.tahi;
+	lsb = ciab.talo;
+	msb = ciab.tahi;
+	if (msb != tmp)
+		lsb = ciab.talo;
 
-	if (ticks > jiffy_ticks / 2)
+	if (msb > 0)
 		/* check for pending interrupt */
 		if (cia_set_irq(&ciab_base, 0) & CIA_ICR_TA)
-			offset = 10000;
+			offset = jiffy_ticks;
+
+	ticks = jiffy_ticks - (msb << 8 | lsb);
+	ticks += offset + clk_total;
 
-	ticks = jiffy_ticks - ticks;
-	ticks = (10000 * ticks) / jiffy_ticks;
+	local_irq_restore(flags);
 
-	return (ticks + offset) * 1000;
+	return ticks;
 }
 
 static void amiga_reset(void)  __noreturn;
-- 
2.18.1