[PATCH RESEND] ixp4xx: clockevent set_next_event fix
Richard Cochran
richardcochran at gmail.com
Tue Feb 14 07:01:53 EST 2012
On Tue, Feb 14, 2012 at 10:55:05AM +0100, Micha?? Wr??bel wrote:
> IXP43x Developer's Manual [17.4.3] and IXP4[56]x Developer's Manual
> [18.4.3] say that for predictable operation the timer needs to be
> stopped before writing a new value into the reload register. Indeed,
> tests on IXP435 show that writing a new value into the reload register
> without stopping the timer first has no immediate effect on the timer.
> This makes hrtimers started through hrtimer_start() to be delayed until
> the currently earliest hrtimer expires.
>
> IXP42x Developer's Manual [14.3] says that the timer will be reloaded
> immediately on setting the timer reload register, so the bug probably
> doesn't occur on those CPUs. However, stopping the timer shouldn't have
> any negative side effects, so it should be safe to apply it
> machine-wide.
Unless you test this out and confirm that it works for all IXP4xx, I
would prefer to see a specific timer function for the 43x instead.
Thanks,
Richard
>
> Signed-off-by: Micha?? Wr??bel <michal.wrobel at flytronic.pl>
> ---
> arch/arm/mach-ixp4xx/common.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> The previous patch had a mistake in the description - wrong reference to
> "General-Purpose Timers" section in IXP42x Developer's Manual.
>
> diff --git a/arch/arm/mach-ixp4xx/common.c b/arch/arm/mach-ixp4xx/common.c
> index 3841ab4..fd37c83 100644
> --- a/arch/arm/mach-ixp4xx/common.c
> +++ b/arch/arm/mach-ixp4xx/common.c
> @@ -434,6 +434,7 @@ static int ixp4xx_set_next_event(unsigned long evt,
> {
> unsigned long opts = *IXP4XX_OSRT1 & IXP4XX_OST_RELOAD_MASK;
>
> + *IXP4XX_OSRT1 = 0;
> *IXP4XX_OSRT1 = (evt & ~IXP4XX_OST_RELOAD_MASK) | opts;
>
> return 0;
> --
> 1.7.5.4
>
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