Permission denied when accessing STM2 SoC Level Time Source

[kawin]

Hi all,

I'm getting the following errors when trying to use the STM2 driver as shown in Chapter 14: SoC Level Time Source in the Linux BSP 30.0 user manual. 

Init driver

root@s32g274ardb2:~# echo 1 > /sys/devices/platform/40124000.stm/init
-sh: /sys/devices/platform/40124000.stm/init: Permission denied

Reading Timer Value 

root@s32g274ardb2:~# cat /sys/devices/platform/40124000.stm/value
cat: /sys/devices/platform/40124000.stm/value: No such file or directory

The kernel has been patched successfully and bitbake virtual/kernel generated Image and dtb without any errors. This is confirmed by looking at the runtime kernel config:

root@s32g274ardb2:~# zcat /proc/config.gz | grep GLOBAL
CONFIG_FSL_GLOBAL_TIME_STM=m

Kernel Config

In fsl-s32-gen1.dtsi (tmp/work/s32g274ardb2-fsl-linux/linux-s32/5.10.41-r0/git/arch/arm64/boot/dts/freescale/fsl-s32-gen1.dtsi), I changed the status of the STM2 device node to "okay":

stm2: stm@40124000{
	compatible = "fsl,s32gen1-stm-global";
	reg = <0x0 0x40124000 0x0 0x3000>;
	clocks = <&clks S32GEN1_SCMI_CLK_STM_MODULE>;
	clock-names = "stm";
	status = "okay";
};

In s32gen1_defconfig (tmp/work/s32g274ardb2-fsl-linux/linux-s32/5.10.41-r0/git/arch/arm64/configs/s32gen1_defconfig) CONFIG_FSL_GLOBAL_TIME_STM=m was appended to the end like so:

...
# CONFIG_RUNTIME_TESTING_MENU is not set
CONFIG_FSL_GLOBAL_TIME_STM=m

I then created a patch and copied it to sources/meta-alb/recipes-kernel/linux/linux-s32, which get append to the end of linux-s32_5.10.bb file like so:

...
SRC_URI += " file://0001-Enable-Global-Time-Source-and-STM2-device-tree.patch"

After this, kernel is cleaned and build with the following commands:

bitbake -c cleansstate virtual/kernel
bitbake virtual/kernel

 The output Image and DTS file is transferred to SD card FAT partition and everything booted up successfully.

[andrei_skok · Accepted solution]

Hi Kawin

Sorry, I misunderstood your question before.

There is nothing wrong with your operation. Did you forget to load the '*stm.ko' module ?

In addition, you can run the 'git status' command in the linux kernel directory to check whether the patch has been applied.

[andrei_skok]

Hi Kawin

In s32gen1_defconfig (tmp/work/s32g274ardb2-fsl-linux/linux-s32/5.10.41-r0/git/arch/arm64/configs/s32gen1_defconfig) CONFIG_FSL_GLOBAL_TIME_STM=m

That is not going to work. You should enable the global stm timer from menuconfig menu with 'bitbake -c menuconfig virtual/kernel'.

Device Drivers ->Clock Source drivers->

save and re-compile the kernel.

Below is the test procedure

step1. Boot to reach the Linux console.

step2. Insert the 'fsl_global_time.ko' kernel module with "insmod /lib/modules/5.10.41-rt42+g98b692708f63/kernel/drivers/clocksource/fsl_global_time.ko"

step3. 

This should be a document description error.

[kawin]

Hi Andrei,

Could you give me some explanation on why patching defconfig directly wouldn't work? Is there a mistake in the documentation? In any case, should general procedure of patch -> clean -> build work? Since a patch should get applied before the compilation.

Thank you,

Kawin