i.MX233: System freeze after enabling CLKSEQ_BYPASS_CPU

[lategoodbye]

Hi,

want to reduce cpu frequency of the i.MX23 (LQFP 128 pin) to 24 MHz for standby. Unfortunately the Linux system (Kernel 4.5) freeze after enabling CLKCTRL_CLKSEQ_BYPASS_CPU.

Here a register dump before modifing CLKCTRL_CLKSEQ_BYPASS_CPU:

HW_CLKCTRL_HBUS   = 0x00000003
HW_CLKCTRL_CPU    = 0x00011001
HW_CLKCTRL_CLKSEQ = 0x0000011A
HW_CLKCTRL_EMI    = 0x00000102

What could be the reason for this behavior?

[lategoodbye]

I moved code for the clock switching in OCRAM, but it shows the same behavior.

Then i did the same in U-Boot which leads to Data abort R14 and a bootloop.

I also tried the Freescale Kernel 2.6.35 which also show no reaction to resume.

Btw here is the naming of the i.MX233:

MCIMX233CAG4C

A5 M88S

XAA1132A

[Yuri]

Hello,

  What Linux is used in the case ?

NXP recent release is

https://www.nxp.com/webapp/Download?colCode=L2.6.31_10.05.00_SDK_SOURCE&appType=license&location=nul...

Perhaps it makes sense to post this issue to meta-fsl-arm mailing list,
since there is no official NXP release for kernel 4.5

https://lists.yoctoproject.org/listinfo/meta-freescale

Have a great day,
Yuri

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[lategoodbye]

Hello Yuri,

it's the mainline kernel. I'm trying to port standby support to mainline.

I stuck on this line in my Linux 4.5 repo (which actually enabling CLKCTRL_CLKSEQ_BYPASS_CPU):

linux-2.6-imx.git - Freescale i.MX Linux Tree​

This is my code:

linux-mxs-power/pm.c at rebase-4.5 · lategoodbye/linux-mxs-power · GitHub

I think my issue is related to a wrong or missing register settings which causes the freeze, because i don't get any debug output after this call.

Are there any constraints before enabling CLKCTRL_CLKSEQ_BYPASS_CPU?

Edit:

Do the code to switch BYPASS_CPU must run from OCRAM?

Do i take care of HBUS or XBUS clock setting?

[Yuri]

Hello,

the following may be helpful :

linux-2.6.28.mx233-falconwing/sleep.S at master · xobs/linux-2.6.28.mx233-falconwing · GitHub

Regards,

Yuri.

[lategoodbye]

Hi Yuri,

i added debug messages after each instruction. The issue appears before entering the suspend function in OCRAM, directly after:

if (clk_set_parent(cpu_clk, osc_clk) < 0) {

I will try to move this code into OCRAM.