Linux/PROCESSOR-SDK-AM335X: Disable RTC

Ugnius Subacius

Expert 1180 points

Part Number: PROCESSOR-SDK-AM335X

Tool/software: Linux

I am trying to disable RTC on the linux 4.4.41 kernel.

* I changed the RTC status to disabled in .dts file.

* Removed the RTC entries in the config file.

*tried removing am33xx_l4_wkup__rtc from array am33xx_hwmod_ocp_ifs from kernel source code, as described here:

https://e2e.ti.com/support/arm/sitara_arm/f/791/t/485319?tisearch=e2e-quicksearch&keymatch=remove%20rtc

The board boots up fine without the crystal.

However, some errors can be seen on the kernel boot log:

[ 14.231638] pm33xx: Unknown symbol rtc_write_scratch (err 0)
[ 14.231666] pm33xx: Unknown symbol rtc_class_open (err 0)
[ 14.231709] pm33xx: Unknown symbol rtc_read_scratch (err 0)

[ 14.455049] pm33xx: Unknown symbol rtc_write_scratch (err 0)
[ 14.455079] pm33xx: Unknown symbol rtc_class_open (err 0)
[ 14.455122] pm33xx: Unknown symbol rtc_read_scratch (err 0)

Does anyone know why that is?

Kind regards,

Ugnius

over 8 years ago

0 Yordan Kovachev over 8 years ago

TI__Guru**** 161600 points

Hi Ugnius,

Which dts files did you modify? Have in mind that you have the rtc defined in am33xx.dtsi file as well.

Best Regards,
Yordan

0 Yordan Kovachev over 8 years ago in reply to Yordan Kovachev

TI__Guru**** 161600 points

Also check if your u-boot enables the RTC.

Best Regards,
Yordan

0 Ugnius Subacius over 8 years ago in reply to Yordan Kovachev

Expert 1180 points

Hi Yordan,

I did not realize the am33xx.dtsi file was used, I thought am335x-evmsk.dts was the only file needed to be modified in the dts folder.

I tried adding status = "disabled"; in the .dtsi file RTC section, but the same errors can be seen in boot log.

The u-boot config does not have RTC mentioned. Printing the u-boot environment, the RTC is not mentioned either.

So I assume the u-boot does not try to start the RTC.

Kind regards,

Ugnius

0 Ugnius Subacius over 8 years ago

Expert 1180 points

Hi,

It looks like I was not rebuilding the file system.

From the root of the SDK I tried running make linux_install in addition to make linux.
This printed message that file system was updated.

After a target re-boot there are no RTC prints on the boot log.

Kind regards,
Ugnius

0 Yordan Kovachev over 8 years ago in reply to Ugnius Subacius

TI__Guru**** 161600 points

Thanks for updating the thread.

Best Regards,
Yordan

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Linux/PROCESSOR-SDK-AM335X: Disable RTC