How to set imx6UL CPU to 528MHz in U-boot

[x10]

Hi, all

I have measured the voltage of TP702 in imx6ul-evk is 1.4V, but CPU frequency is only 396MHz in U-boot. Are there any way to set it to 528MHz? BTW, I can not understand the meaning of following description in imx6UL RM p.157:

Target frequency of the core (including Neon and L1 cache) is 528 MHz non-overdrive

over the specified temperature range:

• 528 MHz non-overdrive over the specified temperature range

Thanks for explanation.

BR

Cheng Shi

[dluberger]

i'm also trying to change u-boot clock frequency. I'm not seeing how to do it from anything in this thread. i can find the soc.c code and the cpu init function; but I'm using the imx6sx processor and its reference manual doesn't go into detail as to how to write c code to change the processor frequency. The solox runs at 792MHz when u-boot is running, and that draws too much power for my hardware. I want u-boot to run at the lowest frequency (198MHz?).

[sourabhdas]

Hi, can anyone please share the code changes in arch_cpu_init() in arch/arm/cpu/armv7/mx6/soc.c to change the clock from 396MHz to 528MHz.

[igorpadykov · Accepted solution]

Hi Cheng

I am afraid this is not supported, but one can add codes for example  to

arch/arm/cpu/armv7/mx6/soc.c, arch_cpu_init(). Procedure is described in

sect.18.5.1.5.3 PLL clock change i.MX6UL RM, that is bypass CCM_ANALOG_PLL_ARMn,

change pll then wait for lock, remove bypass.

uboot-imx.git - Freescale i.MX u-boot Tree

Best regards

igor

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[x10]

Hi, Igor

Thanks for quick reply. Actually I have simply change PLL without bypass, CPU seems work OK on 528 MHz. Is it possible to damage the chip?

In section 18.5.1.5.3 PLL clock change, the change procedure is "power down -> change PLL then wait for lock -> power up", compared with "bypass -> change PLL then wait lock -> remove bypass". Which one is right?

BR

Cheng Shi

[igorpadykov]

Hi Cheng

more right is section 18.5.1.5.3, however seems other options also work.

Chip will not damaged if datasheet working conditions  are not exceeded.

Best regards

igor

[x10]

Hi Igor

My final change is with "bypass -> change PLL then wait lock -> remove bypass" which seems more reasonable. Thanks for your help. Further more, the clock range of ARM PLL is from 648 MHz to 1296 MHz. Does this mean it should be okay to set CPU clock higher than 528 MHz, for example to 600 MHz?

BR

Cheng Shi

[yuvrajdodia]

Hi Cheng,

I would like to change imx6ul CPU clock from 396 Mhz to 528 Mhz.

I am new to imx6ul and u-boot.

I try to understand arch_cpu_init() in arch/arm/cpu/armv7/mx6/soc.c but don't get how to "bypass -> change PLL then wait lock -> remove bypass".

If possible change you share your change in u-boot related to change CPU clock from 396 Mhz to 528 Mhz.

Thanks,

Yuvi

[igorpadykov]

according to datasheet 528MHz is max. frequency

http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6ULCEC.pdf

~igor