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Commit 81d4f7bfdc9417e7d8fc1133c762daa4458eec5e

Authored by Tomasz Figa
Committed by Olof Johansson
1 parent 6fe4dfd041
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

clocksource: samsung_pwm_timer: Work around rounding errors in clockevents core 

Due to rounding errors in clockevents core (in conversions between ticks
and nsecs), it might happen that the set_next_event callback gets called
with cycles = 0, causing the code to incorrectly program the PWM timer.

This patch modifies the callback to program the timer for 1 tick, if
received tick count value is 0.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

Showing 1 changed file with 13 additions and 0 deletions Side-by-side Diff

drivers/clocksource/samsung_pwm_timer.c
Diff comments   View file @ 81d4f7b
... ... @@ -176,6 +176,19 @@
176 176 static int samsung_set_next_event(unsigned long cycles,
177 177 struct clock_event_device *evt)
178 178 {
  179 + /*
  180 + * This check is needed to account for internal rounding
  181 + * errors inside clockevents core, which might result in
  182 + * passing cycles = 0, which in turn would not generate any
  183 + * timer interrupt and hang the system.
  184 + *
  185 + * Another solution would be to set up the clockevent device
  186 + * with min_delta = 2, but this would unnecessarily increase
  187 + * the minimum sleep period.
  188 + */
  189 + if (!cycles)
  190 + cycles = 1;
  191 +
179 192 samsung_time_setup(pwm.event_id, cycles);
180 193 samsung_time_start(pwm.event_id, false);
181 194