Thx for your response. I was able to get the LDO021 pin powered on Friday, by re-engineering exactly this file from the linux driver implementation. All the values needed are mentioned in the hi655x_regulator regulators[] array of linux/drivers/regulator/hi655x-regulator.c added to hikey_hi6553_init function.

It's a pity, that HiSilicon doesn't make the documentations public. Seems to be a very interesting and high configurable PMIC.


On February 14, 2016 at 4:39 AM Guodong Xu <> wrote:

On 11 February 2016 at 21:23, git git <> wrote:

Hi devs,

until now, I used 1.8V from the UART Debug Header to power my i2c device, because I thought it is electrically gone on my board. But after testing it with another HiKey Board (this time from LeMaker) with the same Firmware, I'm sure it has to be enabled anywhere. In the linux device tree source I found the following lines


                        ldo21: ldo21@a40 {
                                regulator-compatible = "LDO21";
                                regulator-min-microvolt = <1650000>;
                                regulator-max-microvolt = <2000000>;
                                regulator-enable-ramp-delay = <120>;

But, how to do this in Bare Metal? LDO5_1V8 seems to be enabled by default  but I can't find where it is done. How to configure the PMIC in early Bootloader stage?

You need to read the code in

Unfortunately, we provide no public document on PMIC chip (hi655x) used on HiKey. But register information can be reverse engineered from driver code above.

.enable_reg = HI655X_BUS_ADDR(ereg), \
 .enable_mask = BIT(cmask), \
enable_reg is the register to write 1 to to enable a regulator. Band enable_mask is the bit for it. Each bit for one ldo.

Similarly you see the disable_reg and vreg.



Hope someone can solve this riddle for me.

Best Regards

On February 3, 2016 at 7:15 PM Grant Likely <> wrote:

I just checked. The 4.4 kernel does not enable the 1.8V voltage rail
on the LS expansion connector. Do you know how to enable it?

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