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From c7e39ba40085693541595bee4604b70f2b716915 Mon Sep 17 00:00:00 2001
From: Benedikt Spranger <b.spranger@linutronix.de>
Date: Mon, 8 Mar 2010 18:57:04 +0100
Subject: [PATCH] Atmel TCLIB: Allow higher clock rates for clock events
commit 917c377817e393775fb6a2eaf961c153e38760fd in tip.
As default the TCLIB uses the 32KiHz base clock rate for clock events.
Add a compile time selection to allow higher clock resulution.
Signed-off-by: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
drivers/clocksource/tcb_clksrc.c | 44 ++++++++++++++++++++++---------------
drivers/misc/Kconfig | 11 +++++++-
2 files changed, 35 insertions(+), 20 deletions(-)
diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
index 01b886e..90350b6 100644
--- a/drivers/clocksource/tcb_clksrc.c
+++ b/drivers/clocksource/tcb_clksrc.c
@@ -21,8 +21,7 @@
* resolution better than 200 nsec).
*
* - The third channel may be used to provide a 16-bit clockevent
- * source, used in either periodic or oneshot mode. This runs
- * at 32 KiHZ, and can handle delays of up to two seconds.
+ * source, used in either periodic or oneshot mode.
*
* A boot clocksource and clockevent source are also currently needed,
* unless the relevant platforms (ARM/AT91, AVR32/AT32) are changed so
@@ -68,6 +67,7 @@ static struct clocksource clksrc = {
struct tc_clkevt_device {
struct clock_event_device clkevt;
struct clk *clk;
+ u32 freq;
void __iomem *regs;
};
@@ -76,13 +76,6 @@ static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
return container_of(clkevt, struct tc_clkevt_device, clkevt);
}
-/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
- * because using one of the divided clocks would usually mean the
- * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
- *
- * A divided clock could be good for high resolution timers, since
- * 30.5 usec resolution can seem "low".
- */
static u32 timer_clock;
static void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
@@ -105,11 +98,12 @@ static void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
case CLOCK_EVT_MODE_PERIODIC:
clk_enable(tcd->clk);
- /* slow clock, count up to RC, then irq and restart */
+ /* count up to RC, then irq and restart */
__raw_writel(timer_clock
| ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
- __raw_writel((32768 + HZ/2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
+ __raw_writel((tcd->freq + HZ/2)/HZ,
+ tcaddr + ATMEL_TC_REG(2, RC));
/* Enable clock and interrupts on RC compare */
__raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
@@ -122,7 +116,7 @@ static void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
case CLOCK_EVT_MODE_ONESHOT:
clk_enable(tcd->clk);
- /* slow clock, count up to RC, then irq and stop */
+ /* count up to RC, then irq and stop */
__raw_writel(timer_clock | ATMEL_TC_CPCSTOP
| ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
@@ -152,8 +146,12 @@ static struct tc_clkevt_device clkevt = {
.features = CLOCK_EVT_FEAT_PERIODIC
| CLOCK_EVT_FEAT_ONESHOT,
.shift = 32,
+#ifdef CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
/* Should be lower than at91rm9200's system timer */
.rating = 125,
+#else
+ .rating = 200,
+#endif
.set_next_event = tc_next_event,
.set_mode = tc_mode,
},
@@ -179,8 +177,9 @@ static struct irqaction tc_irqaction = {
.handler = ch2_irq,
};
-static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
+static void __init setup_clkevents(struct atmel_tc *tc, int divisor_idx)
{
+ unsigned divisor = atmel_tc_divisors[divisor_idx];
struct clk *t2_clk = tc->clk[2];
int irq = tc->irq[2];
@@ -188,11 +187,17 @@ static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
clkevt.clk = t2_clk;
tc_irqaction.dev_id = &clkevt;
- timer_clock = clk32k_divisor_idx;
+ timer_clock = divisor_idx;
- clkevt.clkevt.mult = div_sc(32768, NSEC_PER_SEC, clkevt.clkevt.shift);
- clkevt.clkevt.max_delta_ns
- = clockevent_delta2ns(0xffff, &clkevt.clkevt);
+ if (!divisor)
+ clkevt.freq = 32768;
+ else
+ clkevt.freq = clk_get_rate(t2_clk)/divisor;
+
+ clkevt.clkevt.mult = div_sc(clkevt.freq, NSEC_PER_SEC,
+ clkevt.clkevt.shift);
+ clkevt.clkevt.max_delta_ns =
+ clockevent_delta2ns(0xffff, &clkevt.clkevt);
clkevt.clkevt.min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;
clkevt.clkevt.cpumask = cpumask_of(0);
@@ -295,8 +300,11 @@ static int __init tcb_clksrc_init(void)
clocksource_register(&clksrc);
/* channel 2: periodic and oneshot timer support */
+#ifdef CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
setup_clkevents(tc, clk32k_divisor_idx);
-
+#else
+ setup_clkevents(tc, best_divisor_idx);
+#endif
return 0;
}
arch_initcall(tcb_clksrc_init);
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 2d883bb..652af64 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -54,8 +54,7 @@ config ATMEL_TCB_CLKSRC
are combined to make a single 32-bit timer.
When GENERIC_CLOCKEVENTS is defined, the third timer channel
- may be used as a clock event device supporting oneshot mode
- (delays of up to two seconds) based on the 32 KiHz clock.
+ may be used as a clock event device supporting oneshot mode.
config ATMEL_TCB_CLKSRC_BLOCK
int
@@ -69,6 +68,14 @@ config ATMEL_TCB_CLKSRC_BLOCK
TC can be used for other purposes, such as PWM generation and
interval timing.
+config ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK
+ bool "TC Block use 32 KiHz clock"
+ depends on ATMEL_TCB_CLKSRC
+ default y
+ help
+ Select this to use 32 KiHz base clock rate as TC block clock
+ source for clock events.
+
config IBM_ASM
tristate "Device driver for IBM RSA service processor"
depends on X86 && PCI && INPUT && EXPERIMENTAL
--
1.7.0.4
|
