[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>

1 files changed, 50 insertions, 36 deletions

diff --git a/arch/arm/mach-imx/time.c b/arch/arm/mach-imx/time.c
index 8ae4a2c5066f..40039b2a90b3 100644
--- 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,
 };