RK3399 CPU/GPU/DDR定频

调试问题有时需要定频，方法有两种：一种修改内核频率配置表，一种用户层命令操作。

内核修改的方法就是将opp 频率表中不用的频率disable掉，在节点中添加status = "disabled",比如：

opp-600000000 {
            opp-hz = /bits/ 64 <600000000>;
            opp-microvolt = <825000 825000 1250000>;
            opp-microvolt-L0 = <825000 825000 1250000>;
            opp-microvolt-L1 = <825000 825000 1250000>;
            opp-microvolt-L2 = <825000 825000 1250000>;
            opp-microvolt-L3 = <825000 825000 1250000>;
            clock-latency-ns = <40000>;

            status = "disabled";
        };

只留需要定频的频率即可。

在不修改内核的情况下可以通过用户层操作命令定频，比如定频CPU频率：

/* 切换小核governor到userspace */
echo userspace > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
/* 设置小核216MHz */
echo 216000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed
/* 切换大核governor到userspace */
echo userspace > /sys/devices/system/cpu/cpufreq/policy4/scaling_governor
/* 设置大核408MHz */
echo 408000 > /sys/devices/system/cpu/cpufreq/policy4/scaling_setspeed

定频GPU频率：

/* 切换到userspace，不一定是ff400000.gpu，根据不同的平台修改 */
echo userspace > /sys/class/devfreq/ff9a0000.gpu/governor
/* 设置400MHz */
echo 400000000 > /sys/class/devfreq/ff9a0000.gpu/userspace/set_freq
/* 查看当前频率 */
cat /sys/class/devfreq/ff9a0000.gpu/cur_freq