clocksource: convert SPEAr platforms 16-bit up counting clocksource

Convert SPEAr platforms 16-bit up counting clocksource, which requires
a 16-bit register access read rather than 32-bit.
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -884,6 +884,7 @@ config PLAT_SPEAR
 	select ARM_AMBA
 	select ARCH_REQUIRE_GPIOLIB
 	select CLKDEV_LOOKUP
+	select CLKSRC_MMIO
 	select GENERIC_CLOCKEVENTS
 	select HAVE_CLK
 	help

arch/arm/plat-spear/time.c

@@ -70,19 +70,6 @@ static void clockevent_set_mode(enum clock_event_mode mode,
 static int clockevent_next_event(unsigned long evt,
 				 struct clock_event_device *clk_event_dev);
 
-static cycle_t clocksource_read_cycles(struct clocksource *cs)
-{
-	return (cycle_t) readw(gpt_base + COUNT(CLKSRC));
-}
-
-static struct clocksource clksrc = {
-	.name = "tmr1",
-	.rating = 200,		/* its a pretty decent clock */
-	.read = clocksource_read_cycles,
-	.mask = 0xFFFF,		/* 16 bits */
-	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
 static void spear_clocksource_init(void)
 {
 	u32 tick_rate;
@@ -103,7 +90,8 @@ static void spear_clocksource_init(void)
 	writew(val, gpt_base + CR(CLKSRC));
 
 	/* register the clocksource */
-	clocksource_register_hz(&clksrc, tick_rate);
+	clocksource_mmio_init(gpt_base + COUNT(CLKSRC), "tmr1", tick_rate,
+		200, 16, clocksource_mmio_readw_up);
 }
 
 static struct clock_event_device clkevt = {