[PATCH] timer optimization part 2.

Woodruff, Richard
2008-04-04T20:11:31Z

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Hi,

This patch adds a new function timer_load_start() which optimizes the
system timer. In tree users have been updated to use this function.

This was tested and working on a pull as of 4 April 08 on
2.6.25-rc8-omap1-04408-g722c80b on 3430SDP. A previous version has been
working with out issue for a while now.

* Before patch register writes are taking up .078% @ 500MHz.

Address |total |min |max |avr |count|ratio%
old\process\default_idle|7.369s |0.0us|999.902ms|14.477ms|509. |62.661%
ld\Global\cpu_v7_do_idle|4.265s |0.0us|375.786ms|24.374ms|175. |36.270%
(UNKNOWN)|17.503ms|0.us|531.080us|5.119us|3419. |0.148%
r\omap_dm_timer_set_load|8.135ms|0.0us|79.887us|15.065us|540. |0.069%
<--
\vmlinux-old\Global\_end|2.023ms|0.0us|4.000us|0.560us|3613. |0.017%
-old\Global\__raw_readsw|1.962ms|0.0us|108.610us|9.167us|214. |0.016%
old\smc91x\smc_interrupt|1.353ms|0.0us|10.212us|2.348us|576. |0.011%
s/namei\__link_path_walk|1.161ms|0.0us|4.310us|0.762us| 1524. |0.009%
\omap_dm_timer_write_reg|1.085ms|0.0us|126.150us|2.153us|504. |0.009%
<--

* After patch timer functions do not show up in top listings.

Regards,
Richard W.

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This patch optimizes the timer load and start sequence. By combining the
load and start a needless posted wait can be removed from the system timer
execution path.

* Before patch register writes are taking up .078% @ 500MHz during idle.

Address |total |min |max |avr |count|ratio%
old\process\default_idle|7.369s |0.0us|999.902ms|14.477ms|509. |62.661%
ld\Global\cpu_v7_do_idle|4.265s |0.0us|375.786ms|24.374ms|175. |36.270%
(UNKNOWN)|17.503ms|0.us|531.080us|5.119us|3419. |0.148%
r\omap_dm_timer_set_load|8.135ms|0.0us|79.887us|15.065us|540. |0.069% <--
\vmlinux-old\Global\_end|2.023ms|0.0us|4.000us|0.560us|3613. |0.017%
-old\Global\__raw_readsw|1.962ms|0.0us|108.610us|9.167us|214. |0.016%
old\smc91x\smc_interrupt|1.353ms|0.0us|10.212us|2.348us|576. |0.011%
s/namei\__link_path_walk|1.161ms|0.0us|4.310us|0.762us| 1524. |0.009%
\omap_dm_timer_write_reg|1.085ms|0.0us|126.150us|2.153us|504. |0.009% <--

* After patch timer functions do not show up in top listings for long captures.

Signed-off-by: Richard Woodruff <r-woodruff2@ti.com>

diff --git a/arch/arm/mach-omap2/timer-gp.c b/arch/arm/mach-omap2/timer-gp.c
index 78d05f2..557603f 100644
--- a/arch/arm/mach-omap2/timer-gp.c
+++ b/arch/arm/mach-omap2/timer-gp.c
@@ -59,8 +59,7 @@ static struct irqaction omap2_gp_timer_irq = {
static int omap2_gp_timer_set_next_event(unsigned long cycles,
struct clock_event_device *evt)
{
- omap_dm_timer_set_load(gptimer, 0, 0xffffffff - cycles);
- omap_dm_timer_start(gptimer);
+ omap_dm_timer_set_load_start(gptimer, 0, 0xffffffff - cycles);

return 0;
}
@@ -77,8 +76,7 @@ static void omap2_gp_timer_set_mode(enum clock_event_mode mode,
period = clk_get_rate(omap_dm_timer_get_fclk(gptimer)) / HZ;
period -= 1;

- omap_dm_timer_set_load(gptimer, 1, 0xffffffff - period);
- omap_dm_timer_start(gptimer);
+ omap_dm_timer_set_load_start(gptimer, 1, 0xffffffff - period);
break;
case CLOCK_EVT_MODE_ONESHOT:
break;
@@ -172,8 +170,7 @@ static void __init omap2_gp_clocksource_init(void)
tick_rate = clk_get_rate(omap_dm_timer_get_fclk(gpt));
tick_period = (tick_rate / HZ) - 1;

- omap_dm_timer_set_load(gpt, 1, 0);
- omap_dm_timer_start(gpt);
+ omap_dm_timer_set_load_start(gpt, 1, 0);

clocksource_gpt.mult =
clocksource_khz2mult(tick_rate/1000, clocksource_gpt.shift);
diff --git a/arch/arm/plat-omap/dmtimer.c b/arch/arm/plat-omap/dmtimer.c
index 822b6bb..f22506a 100644
--- a/arch/arm/plat-omap/dmtimer.c
+++ b/arch/arm/plat-omap/dmtimer.c
@@ -546,6 +546,24 @@ void omap_dm_timer_set_load(struct omap_dm_timer *timer, int autoreload,
omap_dm_timer_write_reg(timer, OMAP_TIMER_TRIGGER_REG, 0);
}

+/* Optimized set_load which removes costly spin wait in timer_start */
+void omap_dm_timer_set_load_start(struct omap_dm_timer *timer, int autoreload,
+ unsigned int load)
+{
+ u32 l;
+
+ l = omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
+ if (autoreload)
+ l |= OMAP_TIMER_CTRL_AR;
+ else
+ l &= ~OMAP_TIMER_CTRL_AR;
+ l |= OMAP_TIMER_CTRL_ST;
+
+ omap_dm_timer_write_reg(timer, OMAP_TIMER_COUNTER_REG, load);
+ omap_dm_timer_write_reg(timer, OMAP_TIMER_LOAD_REG, load);
+ omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
+}
+
void omap_dm_timer_set_match(struct omap_dm_timer *timer, int enable,
unsigned int match)
{
@@ -560,7 +578,6 @@ void omap_dm_timer_set_match(struct omap_dm_timer *timer, int enable,
omap_dm_timer_write_reg(timer, OMAP_TIMER_MATCH_REG, match);
}

-
void omap_dm_timer_set_pwm(struct omap_dm_timer *timer, int def_on,
int toggle, int trigger)
{
diff --git a/include/asm-arm/arch-omap/dmtimer.h b/include/asm-arm/arch-omap/dmtimer.h
index fefb276..02b29e8 100644
--- a/include/asm-arm/arch-omap/dmtimer.h
+++ b/include/asm-arm/arch-omap/dmtimer.h
@@ -66,6 +66,7 @@ void omap_dm_timer_stop(struct omap_dm_timer *timer);

void omap_dm_timer_set_source(struct omap_dm_timer *timer, int source);
void omap_dm_timer_set_load(struct omap_dm_timer *timer, int autoreload, unsigned int value);
+void omap_dm_timer_set_load_start(struct omap_dm_timer *timer, int autoreload, unsigned int value);
void omap_dm_timer_set_match(struct omap_dm_timer *timer, int enable, unsigned int match);
void omap_dm_timer_set_pwm(struct omap_dm_timer *timer, int def_on, int toggle, int trigger);
void omap_dm_timer_set_prescaler(struct omap_dm_timer *timer, int prescaler);