Setting correct pm_power_off in kernel 3.14.52

[nexy_sm]

Hi all,

i would like to use gpio-poweroff module in order to completely turn the power off. The Kernel is 3.14.52. This module checks if pm_power_off is NULL and when not it assigns it to its own callback implementation. pm_power_off is a function called at the end of the power down procedure. However, this callback function is set by the driver rtc-svns, which means that gpio_poweroff module cant assign its own callback, since it is not NULL at that point. As an ad-hoc solution I changed the source code and commented a part of the rtc-snvs driver, but I would like to know what should be the proper solution. How could I change the order of loading drivers? Or maybe there is some other solution?

Many thanks

[stasgil]

I'm struggling with pm_power_off myself, but i imagine you want to maybe disable the snvs driver (CONFIG_POWER_RESET_IMX option ), maybe then it won't override your desired function ?

[nexy_sm]

Stas Gil wrote:

I'm struggling with pm_power_off myself, but i imagine you want to maybe disable the snvs driver (CONFIG_POWER_RESET_IMX option ), maybe then it won't override your desired function ?

This is true, I did select snvs driver as a module, but I wanted to ovrcome the problem without doing this. Just by loading gpio-poweroff_ driver first.

[stasgil]

I see.. I think the only way i know would be to change the driver initialization order in do_initcalls() inside the kernel ?

See this: What is the Linux built-in driver load order? - Stack Overflow 

But i'm not sure if snvs and gpio drivers would be the same runlevel.

Also a question for you if you don't mind. At which point does rtc-snvs.c override the pm_power_off function ? I don't seem to be able to find this piece of code, all this driver does for me is suspend clock (kernel 4.1.15)

[nexy_sm]

Also a question for you if you don't mind. At which point does rtc-snvs.c override the pm_power_off function ? I don't seem to be able to find this piece of code, all this driver does for me is suspend clock (kernel 4.1.15)

In probe function, there is:

if (!pm_power_off){

If the function pointer is not null than it will be set. The same principle you can find in the probe function of the gpio-poweroff module. I can at the moment open the source code, but if you struggle to find it, I can post later/

[stasgil]

Hmm i see... So is that in rtc-omap.c driver file ? I thought you meant rtc-snvs.c

[nexy_sm]

linux-fslc/rtc-snvs.c at 3.14-1.0.x-mx6 · Freescale/linux-fslc · GitHub 

line 310

[stasgil]

Huh, i see sorry. I'm on kernel 4.1.15, so i dont have the check for the pm_power_off in that driver.

As i said, i dont think i have any other suggestions, apart from changing init order of the built in modules.

But, you could also change the rtc-snvs driver in menuconfig to M option instead of *, that way you could modprobe this driver on startup in one of the rc scripts. I think that way, your gpio controller might initialize first. This is just an idea.

[joanxie]

for  how to change the source code and build it, pls refer to the yocto training,  tell you how to build your own source code

https://community.nxp.com/docs/DOC-94849