Jon Hunter <jon-hunter@xxxxxx> writes:
> Calling the dmtimer function omap_dm_timer_set_source() fails if following a
> call to pm_runtime_put() to disable the timer. For example the following
> sequence would fail to set the parent clock ...
>
> omap_dm_timer_stop(gptimer);
> omap_dm_timer_set_source(gptimer, OMAP_TIMER_SRC_32_KHZ);
>
> The following error message would be seen ...
>
> omap_dm_timer_set_source: failed to set timer_32k_ck as parent
>
> The problem is that, by design, pm_runtime_put() simply decrements the usage
> count and returns before the timer has actually been disabled. Therefore,
> setting the parent clock failed because the timer was still active when the
> trying to set the parent clock. Setting a parent clock will fail if the clock
> you are setting the parent of has a non-zero usage count. To ensure that this
> does not fail use pm_runtime_put_sync() when disabling the timer.
>
> Note that this will not be seen on OMAP1 devices, because these devices do
> not use the clock framework for dmtimers.
>
> Signed-off-by: Jon Hunter <jon-hunter@xxxxxx>
Acked-by: Kevin Hilman <khilman@xxxxxx>
> ---
> arch/arm/plat-omap/dmtimer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/plat-omap/dmtimer.c b/arch/arm/plat-omap/dmtimer.c
> index 626ad8c..7b6689a 100644
> --- a/arch/arm/plat-omap/dmtimer.c
> +++ b/arch/arm/plat-omap/dmtimer.c
> @@ -258,7 +258,7 @@ EXPORT_SYMBOL_GPL(omap_dm_timer_enable);
>
> void omap_dm_timer_disable(struct omap_dm_timer *timer)
> {
> - pm_runtime_put(&timer->pdev->dev);
> + pm_runtime_put_sync(&timer->pdev->dev);
> }
> EXPORT_SYMBOL_GPL(omap_dm_timer_disable);
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