Re: [PATCH 3/5] ARM: twd: Add context save restore support

Russell King - ARM Linux
2011-01-24T11:11:55Z

On Mon, Jan 24, 2011 at 11:06:09AM +0000, Russell King - ARM Linux wrote:
> On Mon, Jan 24, 2011 at 02:21:17PM +0530, Santosh Shilimkar wrote:
> > In CPU low power state, local timer looses its register context. This
> > patch adds context save restore hooks which can be used by platforms
> > appropriately.
>
> I thought the whole point of CLOCK_EVT_FEAT_C3STOP was that the generic
> timer stuff wouldn't rely on it being kept alive?
>
> Hmm, it looks like we bypass the clockevents code by only setting the
> TWD load value at initialization time, not when we switch to periodic
> mode. We really ought to rewrite it whenever we switch back to periodic
> mode.
>
> I suspect fixing that means you won't need this save/restore support.

Untested, but should do what's required.

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index fd91566..60636f4 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -36,6 +36,7 @@ static void twd_set_mode(enum clock_event_mode mode,
/* timer load already set up */
ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
| TWD_TIMER_CONTROL_PERIODIC;
+ __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
break;
case CLOCK_EVT_MODE_ONESHOT:
/* period set, and timer enabled in 'next_event' hook */
@@ -81,7 +82,7 @@ int twd_timer_ack(void)

static void __cpuinit twd_calibrate_rate(void)
{
- unsigned long load, count;
+ unsigned long count;
u64 waitjiffies;

/*
@@ -116,10 +117,6 @@ static void __cpuinit twd_calibrate_rate(void)
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 1000000) % 100);
}
-
- load = twd_timer_rate / HZ;
-
- __raw_writel(load, twd_base + TWD_TIMER_LOAD);
}

/*