i.MX8M Mini EVK: Changing PMIC Settings in SPL

[david_ochs1]

Hi,

I need to change the settings of an NXP PMIC (PF8121) for a board that's based on the i.MX8M Mini EVK. I see a note on the EVK schematic that mentions a couple of voltage settings for the Rohm PMIC on the EVK are changed in SPL. Is anyone able to give me some guidance on how to do the same thing for the PF8121?

One path I've started down is to try and replicate what's being done on the EVK as close as possible. So far I have found that the power_bd71837_init function from pmic_bd71837.c is being called in SPL, but I can't see yet what else is being done to change the voltages. Does the device tree entry in the u-boot fsl-imx8mm-evk.dts make the changes occur in SPL? If so, how is that controlled - is there a menuconfig option that I haven't found yet?

I hope some of these questions make sense; clearly I don't have much experience with u-boot and SPL. Thanks in advance for your help.

Dave

[igorpadykov]

Hi David

PF8121 is used on boundary devices Nitrogen8M Mini board

https://boundarydevices.com/official-release-of-the-nitrogen8m_mini-featuring-i-mx8m-mini/ 

all pmic settings can be done in spl.c, no need to adjust them in other places

u-boot-imx6/spl.c at boundary-v2018.07 · boundarydevices/u-boot-imx6 · GitHub 

Best regards
igor
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[david_ochs1]

Thanks very much, igorpadykov, I see the SPL code now.

One more thing if you don't mind: How are the various regulators on the EVK controlled while the kernel is running? There must be drivers controlling their voltage setpoints, but the only one that I see show up in the fsl-imx8mm-evk.dts file is buck2:

&A53_0 {
   arm-supply = <&buck2_reg>;
};

For example, I can see that buck8 is being set to 1.1V while the kernel is running:

root@imx8mmevk:~# cat /sys/class/regulator/regulator.10/name
buck8

root@imx8mmevk:~# cat /sys/class/regulator/regulator.10/microvolts
1100000

But I can't see where it's being commanded to that value.

Thanks, as always!

Best,

Dave

[igorpadykov]

Hi Dave

for regulators usage one can look at sect.2.5 Power Management

Linux Manual included in Linux L4.14.98_2.0.0 Documentation

Best regards
igor