clocksource: sh_tmu: compute mult and shift before registration

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@aurel32.net>
Cc: stable@kernel.org
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 11 insertions, 9 deletions

diff --git a/drivers/clocksource/sh_tmu.c b/drivers/clocksource/sh_tmu.c
index 8e44e14ec4c2..de715901b82a 100644
--- a/drivers/clocksource/sh_tmu.c
+++ b/drivers/clocksource/sh_tmu.c
@@ -199,16 +199,8 @@ static cycle_t sh_tmu_clocksource_read(struct clocksource *cs)
 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)
@@ -228,6 +220,16 @@ static int sh_tmu_register_clocksource(struct sh_tmu_priv *p,
         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);
+
         dev_info(&p->pdev->dev, "used as clock source\n");
         clocksource_register(cs);
         return 0;