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From: Greg KH on 1 Jul 2010 17:40
2.6.34-stable review patch. If anyone has any objections, please let me know.

------------------

From: Aurelien Jarno <aurelien(a)aurel32.net>

commit 66f49121ffa41a19c59965b31b046d8368fec3c7 upstream.

Since commit 98962465ed9e6ea99c38e0af63fe1dcb5a79dc25 ("nohz: Prevent
clocksource wrapping during idle"), the CPU of an R2D board never goes
to idle. This commit assumes that mult and shift are assigned before
the clocksource is registered. As a consequence the safe maximum sleep
time is negative and the CPU never goes into idle.

This patch fixes the problem by moving mult and shift initialization
from sh_tmu_clocksource_enable() to sh_tmu_register_clocksource().

Signed-off-by: Aurelien Jarno <aurelien(a)aurel32.net>
Signed-off-by: Paul Mundt <lethal(a)linux-sh.org>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
drivers/clocksource/sh_tmu.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)

--- a/drivers/clocksource/sh_tmu.c
+++ b/drivers/clocksource/sh_tmu.c
@@ -200,16 +200,8 @@ static cycle_t sh_tmu_clocksource_read(s
static int sh_tmu_clocksource_enable(struct clocksource *cs)
{
struct sh_tmu_priv *p = cs_to_sh_tmu(cs);
- int ret;

- ret = sh_tmu_enable(p);
- if (ret)
- return ret;
-
- /* TODO: calculate good shift from rate and counter bit width */
- cs->shift = 10;
- cs->mult = clocksource_hz2mult(p->rate, cs->shift);
- return 0;
+ return sh_tmu_enable(p);
}

static void sh_tmu_clocksource_disable(struct clocksource *cs)
@@ -229,6 +221,16 @@ static int sh_tmu_register_clocksource(s
cs->disable = sh_tmu_clocksource_disable;
cs->mask = CLOCKSOURCE_MASK(32);
cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+ /* clk_get_rate() needs an enabled clock */
+ clk_enable(p->clk);
+ /* channel will be configured at parent clock / 4 */
+ p->rate = clk_get_rate(p->clk) / 4;
+ clk_disable(p->clk);
+ /* TODO: calculate good shift from rate and counter bit width */
+ cs->shift = 10;
+ cs->mult = clocksource_hz2mult(p->rate, cs->shift);
+
pr_info("sh_tmu: %s used as clock source\n", cs->name);
clocksource_register(cs);
return 0;


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