axp803 dcdc2~6,dldo2
axp806 dcdca, dcdcc, dcdcd, cldo2
axp809 dcdc4
まずは資料を集めるところからか

axppmic.c
const struct axppmic_regdata axp809_regdata[] = {
//snip
{ "dcdc4", 0x10, (1 << 4), (1 << 4), (0 << 4),
0x24, 0x3f, 600000, 20000, 1800000, 100000 },

axp809.c
int axp_set_dcdc4(unsigned int mvolt)
{
int ret;
u8 cfg = axp809_mvolt_to_cfg(mvolt, 600, 1540, 20);

if (mvolt >= 1540)
cfg = 0x30 + axp809_mvolt_to_cfg(mvolt, 1800, 2600, 100);