clocksource: convert ARM 32-bit down counting clocksources

Convert SP804, MXC, Nomadik and Orion 32-bit down-counting clocksources
to generic mmio clocksource infrastructure.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Alessandro Rubini <rubini@unipv.it>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/plat-orion/time.c

@@ -80,24 +80,6 @@ static void __init setup_sched_clock(unsigned long tclk)
 	init_sched_clock(&cd, orion_update_sched_clock, 32, tclk);
 }
 
-/*
- * Clocksource handling.
- */
-static cycle_t orion_clksrc_read(struct clocksource *cs)
-{
-	return 0xffffffff - readl(timer_base + TIMER0_VAL_OFF);
-}
-
-static struct clocksource orion_clksrc = {
-	.name		= "orion_clocksource",
-	.rating		= 300,
-	.read		= orion_clksrc_read,
-	.mask		= CLOCKSOURCE_MASK(32),
-	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
-
-
 /*
  * Clockevent handling.
  */
@@ -247,7 +229,8 @@ orion_time_init(u32 _bridge_base, u32 _bridge_timer1_clr_mask,
 	writel(u & ~BRIDGE_INT_TIMER0, bridge_base + BRIDGE_MASK_OFF);
 	u = readl(timer_base + TIMER_CTRL_OFF);
 	writel(u | TIMER0_EN | TIMER0_RELOAD_EN, timer_base + TIMER_CTRL_OFF);
-	clocksource_register_hz(&orion_clksrc, tclk);
+	clocksource_mmio_init(timer_base + TIMER0_VAL_OFF, "orion_clocksource",
+		tclk, 300, 32, clocksource_mmio_readl_down);
 
 	/*
 	 * Setup clockevent timer (interrupt-driven).