Currently cpufreq transition latency value does not really reflect the actual OMAP OPP transition delay. This patch has the actual latency value. I did profile the DVFS latency on OMAP3430, OMAP3630 and OMAP4 for worstcase(MPU and Core together) and found that in none of these platforms, transiton value goes beyong 10ms. Added a buffer of 20ms to avoid too frequent ondemand timer expiry. With this change, performance of ondemand governor is improved when tested using cpufreqbench tool. Without this patch, cpufreq-bench reported ondemand performance as 40% of performance governor, and with this patch it's around 70% (using below procedure).
cpufreq-bench: http://lwn.net/Articles/339862/ http://ftp.riken.go.jp/archives/Linux/suse/people/ckornacker/cpufreq-bench/
Command used for performance testing: cpufreq-bench -l 50000 -s 100000 -x 50000 -y 100000 -g ondemand -r 5 -n 5 -v
Signed-off-by: Vishwanath BS vishwanath.bs@ti.com --- arch/arm/plat-omap/cpu-omap.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) mode change 100644 => 100755 arch/arm/plat-omap/cpu-omap.c
diff --git a/arch/arm/plat-omap/cpu-omap.c b/arch/arm/plat-omap/cpu-omap.c old mode 100644 new mode 100755 index c47faf8..d3fc423 --- a/arch/arm/plat-omap/cpu-omap.c +++ b/arch/arm/plat-omap/cpu-omap.c @@ -158,8 +158,8 @@ static int __init omap_cpu_init(struct cpufreq_policy *policy) policy->max = policy->cpuinfo.max_freq; policy->cur = omap_getspeed(0);
- /* FIXME: what's the actual transition time? */ - policy->cpuinfo.transition_latency = 300 * 1000; + /* Program the actual transition time for worstcase */ + policy->cpuinfo.transition_latency = 30 * 1000;
return 0; }