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authorAaro Koskinen <Aaro.Koskinen@nokia.com>2009-01-29 11:57:17 -0500
committerTony Lindgren <tony@atomide.com>2009-01-29 12:27:00 -0500
commitdf88acbbdc48d0bfe2a46bf2561d984b6d87a9ac (patch)
treeb171f17a12cac4b5ee98e8a98b019857ba70dc0b /arch/arm
parent0dffb5c57a1d76532e2f2c7398579bfce81c3e5c (diff)
ARM: OMAP: gptimer min_delta_ns corrected
When 32 kHz timer is used the min_delta_ns should be initialized so that it reflects the timer programming cost. A write to the timer device will be usually posted, but it takes roughly 3 cycles before it is effective. If the timer is reprogrammed before that, the CPU will stall until the previous write completes. This was pointed out by Richard Woodruff. Since the lower bound for min_delta_ns is 1000, the change is visible only with tick rates less than 3 MHz. Also note that the old value is incorrect for 32 kHz also due to a rounding error, and it can cause the timer queue to hang (due to clockevent code trying to program the timer with zero ticks). Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com> Reviewed-by: Richard Woodruff <r-woodruff2@ti.com> Signed-off-by: Tony Lindgren <tony@atomide.com>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/mach-omap2/timer-gp.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm/mach-omap2/timer-gp.c b/arch/arm/mach-omap2/timer-gp.c
index ae6036300f60..9fc13a2cc3f4 100644
--- a/arch/arm/mach-omap2/timer-gp.c
+++ b/arch/arm/mach-omap2/timer-gp.c
@@ -118,7 +118,8 @@ static void __init omap2_gp_clockevent_init(void)
118 clockevent_gpt.max_delta_ns = 118 clockevent_gpt.max_delta_ns =
119 clockevent_delta2ns(0xffffffff, &clockevent_gpt); 119 clockevent_delta2ns(0xffffffff, &clockevent_gpt);
120 clockevent_gpt.min_delta_ns = 120 clockevent_gpt.min_delta_ns =
121 clockevent_delta2ns(1, &clockevent_gpt); 121 clockevent_delta2ns(3, &clockevent_gpt);
122 /* Timer internal resynch latency. */
122 123
123 clockevent_gpt.cpumask = cpumask_of(0); 124 clockevent_gpt.cpumask = cpumask_of(0);
124 clockevents_register_device(&clockevent_gpt); 125 clockevents_register_device(&clockevent_gpt);