Define a clocksource for the at91rm9200, switching it to use GENERIC_TIME.
(No clockevent support; this is against 2.6.20-rc code.)
Also, slightly streamline reads of the 32KHz counter; if we hit the update
window, we can now use 3 reads not 4.
Signed-off-by: David Brownell <[email protected]>
---
We've been asked to forward stuff to LKML not ARM or RT lists, so ...
arch/arm/mach-at91rm9200/Kconfig | 1
arch/arm/mach-at91rm9200/at91rm9200_time.c | 47 ++++++++++++++++-------------
2 files changed, 28 insertions(+), 20 deletions(-)
NOTE: at91sam926x chips need other solutions. The sam9263 will have two
RTTs; one could work like this 32K timer and the other can be the system's
battery-backed RTC. Otherwise the best bet may be the counter/timer module,
currently not usable from mainstream Linux patchsets. If the board doesn't
need one module for external interfacing, two 16-bit timers can chain to be
a clocksource (I have example code) and the third could issue clockevents
with the same precision (base is multi-MHz vs 32K).
Index: at91/arch/arm/mach-at91rm9200/Kconfig
===================================================================
--- at91.orig/arch/arm/mach-at91rm9200/Kconfig 2006-12-26 12:15:56.000000000 -0800
+++ at91/arch/arm/mach-at91rm9200/Kconfig 2006-12-26 12:16:04.000000000 -0800
@@ -7,6 +7,7 @@ choice
config ARCH_AT91RM9200
bool "AT91RM9200"
+ select GENERIC_TIME
config ARCH_AT91SAM9260
bool "AT91SAM9260"
Index: at91/arch/arm/mach-at91rm9200/at91rm9200_time.c
===================================================================
--- at91.orig/arch/arm/mach-at91rm9200/at91rm9200_time.c 2006-12-26 12:07:36.000000000 -0800
+++ at91/arch/arm/mach-at91rm9200/at91rm9200_time.c 2006-12-26 12:16:04.000000000 -0800
@@ -25,6 +25,7 @@
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/time.h>
+#include <linux/clocksource.h>
#include <asm/hardware.h>
#include <asm/io.h>
@@ -38,33 +39,22 @@ static unsigned long last_crtr;
* The ST_CRTR is updated asynchronously to the master clock. It is therefore
* necessary to read it twice (with the same value) to ensure accuracy.
*/
-static inline unsigned long read_CRTR(void) {
+static inline unsigned long read_CRTR(void)
+{
unsigned long x1, x2;
- do {
- x1 = at91_sys_read(AT91_ST_CRTR);
+ x1 = at91_sys_read(AT91_ST_CRTR);
+ for (;;) {
x2 = at91_sys_read(AT91_ST_CRTR);
- } while (x1 != x2);
+ if (x1 == x2)
+ break;
+ x1 = x2;
+ };
return x1;
}
/*
- * Returns number of microseconds since last timer interrupt. Note that interrupts
- * will have been disabled by do_gettimeofday()
- * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy.
- * 'tick' is usecs per jiffy (linux/timex.h).
- */
-static unsigned long at91rm9200_gettimeoffset(void)
-{
- unsigned long elapsed;
-
- elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV;
-
- return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
-}
-
-/*
* IRQ handler for the timer.
*/
static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
@@ -91,6 +81,20 @@ static struct irqaction at91rm9200_timer
.handler = at91rm9200_timer_interrupt
};
+static cycle_t read_clk32k(void)
+{
+ return read_CRTR();
+}
+
+static struct clocksource clk32k = {
+ .name = "32k_counter",
+ .rating = 200,
+ .read = read_clk32k,
+ .mask = CLOCKSOURCE_MASK(20),
+ .shift = 10,
+ .is_continuous = 1,
+};
+
void at91rm9200_timer_reset(void)
{
last_crtr = 0;
@@ -125,6 +129,10 @@ void __init at91rm9200_timer_init(void)
/* Initialize and enable the timer interrupt */
at91rm9200_timer_reset();
+
+ /* register clocksource */
+ clk32k.mult = clocksource_hz2mult(32768, clk32k.shift);
+ clocksource_register(&clk32k);
}
#ifdef CONFIG_PM
@@ -139,7 +147,6 @@ static void at91rm9200_timer_suspend(voi
struct sys_timer at91rm9200_timer = {
.init = at91rm9200_timer_init,
- .offset = at91rm9200_gettimeoffset,
.suspend = at91rm9200_timer_suspend,
.resume = at91rm9200_timer_reset,
};
-
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