Slow down L138 to 48MHz and 24MHz

Hallo,

I have OMAP-L138 and I use DVSDK 04.03.00.06. (I have LogicPD ZOOM OMAP-L138 EVM as development board)

I want to slow down the clock to 48MHz, and also to 24MHz (possibly with PLL0 bypassed), for consuption purposes.

I have modified the file ~/ti-dvsdk_omapl138-evm_04_03_00_06/psp/linux-2.6.37-psp03.21.00.04.sdk/arch/arm/mach-davinci/da850.c in this way:

static const struct da850_opp da850_opp_96 = {
    .freq        = 96000,
    .prediv        = 1,
    .mult        = 20,
    .postdiv    = 5,
    .cvdd_min    = 1000000,
    .cvdd_max    = 1050000,
};

static const struct da850_opp da850_opp_48 = {
    .freq        = 48000,
    .prediv        = 1,
    .mult        = 20,
    .postdiv    = 10,
    .cvdd_min    = 1000000,
    .cvdd_max    = 1050000,
};

static const struct da850_opp da850_opp_24 = {
    .freq        = 24000,
    .prediv        = 1,
    .mult        = 20,
    .postdiv    = 20,
    .cvdd_min    = 1000000,
    .cvdd_max    = 1050000,
};

#define OPP(freq)         \
    {                \
        .index = (unsigned int) &da850_opp_##freq,    \
        .frequency = freq * 1000, \
    }

static struct cpufreq_frequency_table da850_freq_table[] = {
    OPP(456),
    OPP(408),
    OPP(372),
    OPP(300),
    OPP(200),
    OPP(96),
    OPP(48),
    OPP(24),
    {
        .index        = 0,
        .frequency    = CPUFREQ_TABLE_END,
    },
};

then on the target the new frequencies are correctly listed:

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
456000 408000 372000 300000 200000 96000 48000 24000

but if I try to change the frequency:

# echo 24000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

it hangs. It happens also trying to set 48000.

I cannot understand where I am wrong.

maybe the voltages are wrong?

best regards