iop: clocksource support

This updates the IOP platform to expose the free-running
timer 1 as a clocksource object. This timer is now also
properly initialised, which requires a new write_tcr1()
function from the mach-specific code. Apart from the
explicit initialisation, there is no functional change
in how timer 1 is programmed.

Tested on n2100, compile-tested for all plat-iop machines.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/arch/arm/plat-iop/time.c b/arch/arm/plat-iop/time.c
index 8da95d57c21f..5506c9b45612 100644
--- a/arch/arm/plat-iop/time.c
+++ b/arch/arm/plat-iop/time.c
@@ -19,6 +19,7 @@
 #include <linux/init.h>
 #include <linux/timex.h>
 #include <linux/io.h>
+#include <linux/clocksource.h>
 #include <mach/hardware.h>
 #include <asm/irq.h>
 #include <asm/uaccess.h>
@@ -26,6 +27,43 @@
 #include <asm/mach/time.h>
 #include <mach/time.h>
 
+/*
+ * IOP clocksource (free-running timer 1).
+ */
+static cycle_t iop_clocksource_read(struct clocksource *unused)
+{
+        return 0xffffffffu - read_tcr1();
+}
+
+static struct clocksource iop_clocksource = {
+        .name           = "iop_timer1",
+        .rating         = 300,
+        .read           = iop_clocksource_read,
+        .mask           = CLOCKSOURCE_MASK(32),
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void __init iop_clocksource_set_hz(struct clocksource *cs, unsigned int hz)
+{
+        u64 temp;
+        u32 shift;
+
+        /* Find shift and mult values for hz. */
+        shift = 32;
+        do {
+                temp = (u64) NSEC_PER_SEC << shift;
+                do_div(temp, hz);
+                if ((temp >> 32) == 0)
+                        break;
+        } while (--shift != 0);
+
+        cs->shift = shift;
+        cs->mult = (u32) temp;
+
+        printk(KERN_INFO "clocksource: %s uses shift %u mult %#x\n",
+               cs->name, cs->shift, cs->mult);
+}
+
 static unsigned long ticks_per_jiffy;
 static unsigned long ticks_per_usec;
 static unsigned long next_jiffy_time;
@@ -99,8 +137,15 @@ void __init iop_init_time(unsigned long tick_rate)
          */
         write_trr0(ticks_per_jiffy - 1);
         write_tmr0(timer_ctl);
+
+        /*
+         * Set up free-running clocksource timer 1.
+         */
         write_trr1(0xffffffff);
+        write_tcr1(0xffffffff);
         write_tmr1(timer_ctl);
+        iop_clocksource_set_hz(&iop_clocksource, tick_rate);
+        clocksource_register(&iop_clocksource);
 
         setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
 }