Re: [PATCH] clocksource: save mult_orig in clocksource_disable()

From: john stultz
Date: Thu Jun 18 2009 - 15:17:45 EST


On Fri, 2009-06-19 at 00:24 +0900, Magnus Damm wrote:
> From: Magnus Damm <damm@xxxxxxxxxx>
>
> Save clocksource mult_orig in clocksource_disable().
>
> To fix the common case where ->enable() does not setup
> mult, make sure mult_orig is saved in mult on disable.
>
> Also add comments to explain why we do this.
>
> Signed-off-by: Magnus Damm <damm@xxxxxxxxxx>

Acked-by: John Stultz <johnstul@xxxxxxxxxx>

Thomas, Andrew, please push this for 2.6.31.

thanks
-john


> ---
>
> include/linux/clocksource.h | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> --- 0001/include/linux/clocksource.h
> +++ work/include/linux/clocksource.h 2009-06-19 00:12:16.000000000 +0900
> @@ -293,7 +293,11 @@ static inline int clocksource_enable(str
> if (cs->enable)
> ret = cs->enable(cs);
>
> - /* save mult_orig on enable */
> + /* The frequency may have changed while the clocksource
> + * was disabled. If so the code in ->enable() must update
> + * the mult value to reflect the new frequency. Make sure
> + * mult_orig follows this change.
> + */
> cs->mult_orig = cs->mult;
>
> return ret;
> @@ -309,6 +313,12 @@ static inline int clocksource_enable(str
> */
> static inline void clocksource_disable(struct clocksource *cs)
> {
> + /* Save mult_orig in mult so clocksource_enable() can
> + * restore the value regardless if ->enable() updates
> + * the value of mult or not.
> + */
> + cs->mult = cs->mult_orig;
> +
> if (cs->disable)
> cs->disable(cs);
> }

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