[ARM] 3991/1: i.MX/MX1 high resolution time source

Enhanced resolution for time measurement functions.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/mach-imx/time.c b/arch/arm/mach-imx/time.c
index 8ae4a2c5066fc2a55e7bec5c46377162aa119cc6..40039b2a90b39079a7af6f5fcdd5856f6452280e 100644 (file)
--- a/arch/arm/mach-imx/time.c
+++ b/arch/arm/mach-imx/time.c
@@ -14,6 +14,7 @@
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/time.h>
+#include <linux/clocksource.h>
 
 #include <asm/hardware.h>
 #include <asm/io.h>
@@ -24,33 +25,7 @@
 /* Use timer 1 as system timer */
 #define TIMER_BASE IMX_TIM1_BASE
 
-/*
- * Returns number of us since last clock interrupt.  Note that interrupts
- * will have been disabled by do_gettimeoffset()
- */
-static unsigned long imx_gettimeoffset(void)
-{
-       unsigned long ticks;
-
-       /*
-        * Get the current number of ticks.  Note that there is a race
-        * condition between us reading the timer and checking for
-        * an interrupt.  We get around this by ensuring that the
-        * counter has not reloaded between our two reads.
-        */
-       ticks = IMX_TCN(TIMER_BASE);
-
-       /*
-        * Interrupt pending?  If so, we've reloaded once already.
-        */
-       if (IMX_TSTAT(TIMER_BASE) & TSTAT_COMP)
-               ticks += LATCH;
-
-       /*
-        * Convert the ticks to usecs
-        */
-       return (1000000 / CLK32) * ticks;
-}
+static unsigned long evt_diff;
 
 /*
  * IRQ handler for the timer
@@ -58,14 +33,23 @@ static unsigned long imx_gettimeoffset(void)
 static irqreturn_t
 imx_timer_interrupt(int irq, void *dev_id)
 {
-       write_seqlock(&xtime_lock);
+       uint32_t tstat;
 
        /* clear the interrupt */
-       if (IMX_TSTAT(TIMER_BASE))
-               IMX_TSTAT(TIMER_BASE) = 0;
+       tstat = IMX_TSTAT(TIMER_BASE);
+       IMX_TSTAT(TIMER_BASE) = 0;
+
+       if (tstat & TSTAT_COMP) {
+               do {
+
+                       write_seqlock(&xtime_lock);
+                       timer_tick();
+                       write_sequnlock(&xtime_lock);
+                       IMX_TCMP(TIMER_BASE) += evt_diff;
 
-       timer_tick();
-       write_sequnlock(&xtime_lock);
+               } while (unlikely((int32_t)(IMX_TCMP(TIMER_BASE)
+                                       - IMX_TCN(TIMER_BASE)) < 0));
+       }
 
        return IRQ_HANDLED;
 }
@@ -77,9 +61,9 @@ static struct irqaction imx_timer_irq = {
 };
 
 /*
- * Set up timer interrupt, and return the current time in seconds.
+ * Set up timer hardware into expected mode and state.
  */
-static void __init imx_timer_init(void)
+static void __init imx_timer_hardware_init(void)
 {
        /*
         * Initialise to a known state (all timers off, and timing reset)
@@ -87,7 +71,38 @@ static void __init imx_timer_init(void)
        IMX_TCTL(TIMER_BASE) = 0;
        IMX_TPRER(TIMER_BASE) = 0;
        IMX_TCMP(TIMER_BASE) = LATCH - 1;
-       IMX_TCTL(TIMER_BASE) = TCTL_CLK_32 | TCTL_IRQEN | TCTL_TEN;
+
+       IMX_TCTL(TIMER_BASE) = TCTL_FRR | TCTL_CLK_PCLK1 | TCTL_IRQEN | TCTL_TEN;
+       evt_diff = LATCH;
+}
+
+cycle_t imx_get_cycles(void)
+{
+       return IMX_TCN(TIMER_BASE);
+}
+
+static struct clocksource clocksource_imx = {
+       .name           = "imx_timer1",
+       .rating         = 200,
+       .read           = imx_get_cycles,
+       .mask           = 0xFFFFFFFF,
+       .shift          = 20,
+       .is_continuous  = 1,
+};
+
+static int __init imx_clocksource_init(void)
+{
+       clocksource_imx.mult =
+               clocksource_hz2mult(imx_get_perclk1(), clocksource_imx.shift);
+       clocksource_register(&clocksource_imx);
+
+       return 0;
+}
+
+static void __init imx_timer_init(void)
+{
+       imx_timer_hardware_init();
+       imx_clocksource_init();
 
        /*
         * Make irqs happen for the system timer
@@ -97,5 +112,4 @@ static void __init imx_timer_init(void)
 
 struct sys_timer imx_timer = {
        .init           = imx_timer_init,
-       .offset         = imx_gettimeoffset,
 };

diff --git a/include/asm-arm/arch-imx/timex.h b/include/asm-arm/arch-imx/timex.h
index 8c91674706b1f276e4a08e0f3ba0b73a1a8ef24b..e22ba789546cd8a317e2eb3ae310a8a22dc4931f 100644 (file)
--- a/include/asm-arm/arch-imx/timex.h
+++ b/include/asm-arm/arch-imx/timex.h
@@ -21,7 +21,6 @@
 #ifndef __ASM_ARCH_TIMEX_H
 #define __ASM_ARCH_TIMEX_H
 
-#include <asm/hardware.h>
-#define CLOCK_TICK_RATE                (CLK32)
+#define CLOCK_TICK_RATE                (16000000)
 
 #endif