[PATCH v2] ARM: ks8695: convert to generic time and clocksource

---
  arch/arm/Kconfig            |   3 +-
  arch/arm/mach-ks8695/time.c | 123 +++++++++++++++++++++++++++++++-------------
  2 files changed, 88 insertions(+), 38 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6d6e18f..e9ce038 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -652,8 +652,9 @@ config ARCH_KS8695
  	bool "Micrel/Kendin KS8695"
  	select CPU_ARM922T
  	select ARCH_REQUIRE_GPIOLIB
-	select ARCH_USES_GETTIMEOFFSET
  	select NEED_MACH_MEMORY_H
+	select CLKSRC_MMIO
+	select GENERIC_CLOCKEVENTS
  	help
  	  Support for Micrel/Kendin KS8695 "Centaur" (ARM922T) based
  	  System-on-Chip devices.

diff --git a/arch/arm/mach-ks8695/time.c b/arch/arm/mach-ks8695/time.c
index 6974c23..1ba0182 100644
--- a/arch/arm/mach-ks8695/time.c
+++ b/arch/arm/mach-ks8695/time.c

@@ -25,6 +25,8 @@
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/io.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>

  #include <asm/mach/time.h>
  #include <asm/system_misc.h>

@@ -53,44 +55,68 @@
  /* Timer0 Timeout Counter Register */
  #define T0TC_WATCHDOG		(0xff)		/* Enable watchdog mode */

-/*
- * Returns number of ms since last clock interrupt.  Note that interrupts
- * will have been disabled by do_gettimeoffset()
- */
-static unsigned long ks8695_gettimeoffset (void)
+static void ks8695_set_mode(enum clock_event_mode mode,
+			    struct clock_event_device *evt)
  {
-	unsigned long elapsed, tick2, intpending;
+	if (mode == CLOCK_EVT_FEAT_PERIODIC) {
+		u32 rate = DIV_ROUND_CLOSEST(KS8695_CLOCK_RATE, HZ);
+		u32 half = DIV_ROUND_CLOSEST(rate, 2);
+		u32 tmcon;
+
+		/* Disable timer 1 */
+		tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
+		tmcon &= ~TMCON_T1EN;
+		writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+		/* Both registers need to count down */
+		writel_relaxed(half, KS8695_TMR_VA + KS8695_T1TC);
+		writel_relaxed(half, KS8695_TMR_VA + KS8695_T1PD);
+
+		/* Re-enable timer1 */
+		tmcon |= TMCON_T1EN;
+		writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+	}
+}

-	/*
-	 * Get the current number of ticks.  Note that there is a race
-	 * condition between us reading the timer and checking for an
-	 * interrupt.  We solve this by ensuring that the counter has not
-	 * reloaded between our two reads.
-	 */
-	elapsed = readl_relaxed(KS8695_TMR_VA + KS8695_T1TC) + readl_relaxed(KS8695_TMR_VA + KS8695_T1PD);
-	do {
-		tick2 = elapsed;
-		intpending = readl_relaxed(KS8695_IRQ_VA + KS8695_INTST) & (1 << KS8695_IRQ_TIMER1);
-		elapsed = readl_relaxed(KS8695_TMR_VA + KS8695_T1TC) + readl_relaxed(KS8695_TMR_VA + KS8695_T1PD);
-	} while (elapsed > tick2);
-
-	/* Convert to number of ticks expired (not remaining) */
-	elapsed = (CLOCK_TICK_RATE / HZ) - elapsed;
-
-	/* Is interrupt pending?  If so, then timer has been reloaded already. */
-	if (intpending)
-		elapsed += (CLOCK_TICK_RATE / HZ);
-
-	/* Convert ticks to usecs */
-	return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
+static int ks8695_set_next_event(unsigned long cycles,
+				 struct clock_event_device *evt)
+
+{
+	u32 half = DIV_ROUND_CLOSEST(cycles, 2);
+	u32 tmcon;
+
+	/* Disable timer 1 */
+	tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
+	tmcon &= ~TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+	/* Both registers need to count down */
+	writel_relaxed(half, KS8695_TMR_VA + KS8695_T1TC);
+	writel_relaxed(half, KS8695_TMR_VA + KS8695_T1PD);
+
+	/* Re-enable timer1 */
+	tmcon |= TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+	return 0;
  }

+static struct clock_event_device clockevent_ks8695 = {
+	.name		= "ks8695_t1tc",
+	.rating		= 300, /* Reasonably fast and accurate clock event */
+	.features	= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
+	.set_next_event	= ks8695_set_next_event,
+	.set_mode	= ks8695_set_mode,
+};
+
  /*
   * IRQ handler for the timer.
   */
  static irqreturn_t ks8695_timer_interrupt(int irq, void *dev_id)
  {
-	timer_tick();
+	struct clock_event_device *evt = &clockevent_ks8695;
+
+	evt->event_handler(evt);
  	return IRQ_HANDLED;
  }

@@ -102,18 +128,42 @@ static struct irqaction ks8695_timer_irq = {

  static void ks8695_timer_setup(void)
  {
-	unsigned long tmout = CLOCK_TICK_RATE / HZ;
  	unsigned long tmcon;

-	/* disable timer1 */
+	/* Disable timer 0 and 1 */
  	tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
-	writel_relaxed(tmcon & ~TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
+	tmcon &= ~TMCON_T0EN;
+	tmcon &= ~TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);

-	writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1TC);
-	writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1PD);
+	/*
+	 * Set up timer 0 to loop indefinately, count 32 bits with TOUT0
+	 * set to zero, then 1 bit with TOUT0 set to 1. The reason we are doing
+	 * this is that it's not allowed to set either register to 0, then the
+	 * behaviour is "unpredictable". This injects a faulty pulse every
+	 * 2^32-1 cycles but we can surely live with that rather than
+	 * complicating the code.
+	 */
+	writel_relaxed(0xFFFFFFFFU, KS8695_TMR_VA + KS8695_T0TC);
+	writel_relaxed(1, KS8695_TMR_VA + KS8695_T0PD);
+	/* Start timer 0 */
+	tmcon |= TMCON_T0EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+	/* Use timer 0 as clocksource */
+	if (clocksource_mmio_init((void *) KS8695_TMR_VA + KS8695_T0TC,
+			"ks8695_t0tc", KS8695_CLOCK_RATE, 300, 32,
+			clocksource_mmio_readl_up))
+		pr_err("timer: failed to initialize KS8695 clock source\n");

-	/* re-enable timer1 */
-	writel_relaxed(tmcon | TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
+	/*
+	 * Use timer 1 to fire IRQs on the timeline, only support one-shot
+	 * mode and the system will take care of the rest. Minimum 2 cycles
+	 * (one on each counter) maximum 2*2^32, but the API will only
+	 * accept up to a 32bit full word (0xFFFFFFFFU).
+	 */
+	clockevents_config_and_register(&clockevent_ks8695,
+					KS8695_CLOCK_RATE, 2,
+					0xFFFFFFFFU);
  }

  static void __init ks8695_timer_init (void)

@@ -126,7 +176,6 @@ static void __init ks8695_timer_init (void)

  struct sys_timer ks8695_timer = {
  	.init		= ks8695_timer_init,
-	.offset		= ks8695_gettimeoffset,
  };

  void ks8695_restart(char mode, const char *cmd)