Thread (21 messages) flat view 21 messages, 3 authors, 2017-12-08

Re: [PATCH v8 3/6] clocksource: stm32: increase min delta value

From: Daniel Lezcano <hidden>
Date: 2017-12-08 09:28:29
Also in: linux-arm-kernel, lkml

On 14/11/2017 09:52, Benjamin Gaignard wrote:
quoted hunk ↗ jump to hunk
The CPU is a CortexM4 @ 200MHZ and the clocks driving
the timers are at 90MHZ with a min delta at 1 you could
have an interrupt each 0.01 ms which is really to much.
By increase it to 0x60 it give more time (around 1 ms)
to CPU to handle the interrupt.

Signed-off-by: Benjamin Gaignard <redacted>
---
 drivers/clocksource/timer-stm32.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
index fc61fd1..ae41a19 100644
--- a/drivers/clocksource/timer-stm32.c
+++ b/drivers/clocksource/timer-stm32.c
@@ -36,6 +36,8 @@
 
 #define TIM_EGR_UG	BIT(0)
 
+#define MIN_DELTA	0x60
Explain why 0x60 is a good value.
quoted hunk ↗ jump to hunk
 static int stm32_clock_event_shutdown(struct clock_event_device *evt)
 {
 	struct timer_of *to = to_timer_of(evt);
@@ -129,7 +131,7 @@ static int __init stm32_clockevent_init(struct device_node *node)
 	writel_relaxed(0, timer_of_base(to) + TIM_SR);
 
 	clockevents_config_and_register(&to->clkevt,
-					timer_of_period(to), 0x1, max_delta);
+					timer_of_period(to), MIN_DELTA, max_delta);
 
 	pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n",
 			node, bits);

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