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authorLinus Walleij <linus.walleij@linaro.org>2012-08-29 22:27:22 +0400
committerLinus Walleij <linus.walleij@linaro.org>2012-09-05 10:49:22 +0400
commitc7e783d6adc7798307e7063e11f4127117446d5a (patch)
treeec58ba9e50f3d849527d0ebc914b0c0fe2a903f3
parentd7dda9875b84eb6c2828592b17aa173ac17bf75d (diff)
downloadlinux-c7e783d6adc7798307e7063e11f4127117446d5a.tar.xz
ARM: ks8695: convert to generic time and clocksource
Old platforms using ancient gettimeoffset() and other arcane APIs are standing in the way of cleaning up the ARM kernel. The gettimeoffset() was also broken: it would try to read out the timer counter value, while this would not work (the counter statically returns the initially programmed value) so the implementation would anyway fall back to a homebrew version of jiffie calculation. This is an attempt at blind-coding a generic time and clocksource driver for the platform by way of a datasheet and looking at the old code. Tested-by: Greg Ungerer <gerg@snapgear.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
-rw-r--r--arch/arm/Kconfig3
-rw-r--r--arch/arm/mach-ks8695/time.c105
2 files changed, 69 insertions, 39 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6d6e18fee9fe..e9ce0387f3d7 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 6974c2355601..46c84bc7792c 100644
--- a/arch/arm/mach-ks8695/time.c
+++ b/arch/arm/mach-ks8695/time.c
@@ -25,6 +25,7 @@
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/io.h>
+#include <linux/clockchips.h>
#include <asm/mach/time.h>
#include <asm/system_misc.h>
@@ -53,44 +54,69 @@
/* 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;
+ u32 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;
+ if (mode == CLOCK_EVT_FEAT_PERIODIC) {
+ u32 rate = DIV_ROUND_CLOSEST(KS8695_CLOCK_RATE, HZ);
+ u32 half = DIV_ROUND_CLOSEST(rate, 2);
+
+ /* 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);
+ }
+}
+
+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 +128,22 @@ 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);
-
- writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1TC);
- writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1PD);
+ tmcon &= ~TMCON_T0EN;
+ tmcon &= ~TMCON_T1EN;
+ writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
- /* re-enable timer1 */
- writel_relaxed(tmcon | TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
+ /*
+ * Use timer 1 to fire IRQs on the timeline, 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 +156,6 @@ 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)