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| author | Alexander Kochetkov <al.kochet@gmail.com> | 2017-01-31 15:43:14 +0300 |
|---|---|---|
| committer | Daniel Lezcano <daniel.lezcano@linaro.org> | 2017-04-07 17:23:05 +0300 |
| commit | 5e0a39d0f727b35c8b7ef56ba0724c8ceb006297 (patch) | |
| tree | facd0003d75e6f8b5f9f5230319f8c6fb895fc2f /drivers/clocksource/Kconfig | |
| parent | b72af3462dd8344285f6cc1ba726202b0d4eae20 (diff) | |
| download | linux-5e0a39d0f727b35c8b7ef56ba0724c8ceb006297.tar.xz | |
clocksource/drivers/rockchip_timer: Implement clocksource timer
The clock supplying the arm-global-timer on the rk3188 is coming from the
the cpu clock itself and thus changes its rate everytime cpufreq adjusts
the cpu frequency making this timer unsuitable as a stable clocksource
and sched clock.
The rk3188, rk3288 and following socs share a separate timer block already
handled by the rockchip-timer driver. Therefore adapt this driver to also
be able to act as clocksource and sched clock on rk3188.
In order to test clocksource you can run following commands and check
how much time it take in real. On rk3188 it take about ~45 seconds.
cpufreq-set -f 1.6GHZ
date; sleep 60; date
In order to use the patch you need to declare two timers in the dts
file. The first timer will be initialized as clockevent provider
and the second one as clocksource. The clockevent must be from
alive subsystem as it used as backup for the local timers at sleep
time.
The patch does not break compatibility with older device tree files.
The older device tree files contain only one timer. The timer
will be initialized as clockevent, as expected.
rk3288 (and probably anything newer) is irrelevant to this patch,
as it has the arch timer interface. This patch may be useful
for Cortex-A9/A5 based parts.
Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Diffstat (limited to 'drivers/clocksource/Kconfig')
| -rw-r--r-- | drivers/clocksource/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index 3356ab821624..483f3b1af4fd 100644 --- a/drivers/clocksource/Kconfig +++ b/drivers/clocksource/Kconfig @@ -81,6 +81,7 @@ config ROCKCHIP_TIMER bool "Rockchip timer driver" if COMPILE_TEST depends on ARM || ARM64 select CLKSRC_OF + select CLKSRC_MMIO help Enables the support for the rockchip timer driver. |