[ARM] 4092/1: i.MX/MX1 CPU Frequency scaling latency definition

The transition latency has to be defined and reasonably
small to allow on-demand and conservative governors.
The value has been defined according to manual.
The imx_set_target() protected against seen out of range
requests now.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 13 insertions, 1 deletions

diff --git a/arch/arm/mach-imx/cpufreq.c b/arch/arm/mach-imx/cpufreq.c
index ac5f99895660..4f66e90db74f 100644
--- a/arch/arm/mach-imx/cpufreq.c
+++ b/arch/arm/mach-imx/cpufreq.c
@@ -184,6 +184,17 @@ static int imx_set_target(struct cpufreq_policy *policy,
         long sysclk;
         unsigned int bclk_div = 1;
 
+        /*
+         * Some governors do not respects CPU and policy lower limits
+         * which leads to bad things (division by zero etc), ensure
+         * that such things do not happen.
+         */
+        if(target_freq < policy->cpuinfo.min_freq)
+                target_freq = policy->cpuinfo.min_freq;
+
+        if(target_freq < policy->min)
+                target_freq = policy->min;
+
         freq = target_freq * 1000;
 
         pr_debug(KERN_DEBUG "imx: requested frequency %ld Hz, mpctl0 at boot 0x%08x\n",
@@ -258,7 +269,8 @@ static int __init imx_cpufreq_driver_init(struct cpufreq_policy *policy)
         policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
         policy->cpuinfo.min_freq = 8000;
         policy->cpuinfo.max_freq = 200000;
-        policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
+         /* Manual states, that PLL stabilizes in two CLK32 periods */
+        policy->cpuinfo.transition_latency = 4 * 1000000000LL / CLK32;
         return 0;
 }