How does PMIC and LDO work in Linux??

[andreaszeiler]

Hello,

does anyone know, please, how PMIC and LDO's are configured in Linux 3.0.35? Our boards have iMX6q and dl and solo.

I found a file (arch/arm/mach-mx6/cpu_op-mx6.c) where I can configure some voltages of the cpu. But I don't know how they where configured by Linux.

We want to use our PMIC on the Board to provide a voltage which we setup at linux boot. And the configure the LDO for each voltages (CORE,SOC,...). The problem is that we need a minimum voltage to bootup the board. But in powersafemode (400MHz) the voltage normally is to low. So board doesn't start. I fixed this by changing the cpu_voltage in cpu_op-mx6.c from 950mV to 1,05V. Now the board starts without problems. But we want to set ONE default voltage 1,25V to the PMICs CORE Voltage and regulate it by ldo for the frequencies 1GHz-800MHz-400MHz.

The thing is that I don't find where to set and enable LDO and say to the governor to switch LDO voltage instead of PMIC.

Anyway is there some documentation on freescales linux code? Maybe how's the structure of the code? Where can I change things CPU freq, and so on...? It's difficult to work on it...

Hope someone can help me...

Thanks!

Andi

[Yuri]

  As for power supply voltage setting, mainly it is configured

(after PMIC hardware-coded initialization at power on) in U-boot.

Please refer to “board/freescale/mx6q_sabresd/mx6q_sabresd.c”

for the SDB/SDP designs.

  Further voltages also can be changed dynamically, when using DVFS.

Please look the next chapters in the Linux Reference Manual :

- "CPU Frequency Scaling (CPUFREQ) Driver"

- "Dynamic Bus Frequency Driver)"

- "PF100 Regulator Driver)"

- "Low-level Power Management (PM) Driver"

https://www.freescale.com/webapp/Download?colCode=L3.0.35_4.1.0_LINUX_DOCS&location=null&fasp=1&Pare...

Have a great day,
Yuri

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