STM32MP157a, DSI PLL and DSI-PHY clock configurations in Device tree

[Khaled-ELGHA]

We are doing a custom board bring-up and currently trying to display video on our display device. We use CubeMx to generate the device tree for our project and some user code there. we can see DSI data lanes signals but not DSI clk signal. We did some comparison with stm32mp157f dk2 board and we fond the follwoing when we apply this command to check the clocks in the kernel:

Note: the image version is:

openstlinux-5.15-yocto-kirkstone-mp1-v24.07.17

with a BSP layer on top from somlabs:
https://github.com/SoMLabs/meta-somlabs

cat /sys/kernel/debug/clk/clk_summary | grep -i dsi

The results from the dk2 board:

The result form our custom board:

I have two questions:

1- How can I enable the dsi and the dsi_px? (as the enable count is zero here)
2- How to enable the ck_dsi_phy in my kernel to be used? (like what is shown with the dk2)

Thanks in advance!

[PatrickF]

Hi @Khaled-ELGHA 

any error messages ?

have you looked at https://wiki.st.com/stm32mpu/wiki/DSI_internal_peripheral and  https://wiki.st.com/stm32mpu/wiki/DSI_device_tree_configuration

Maybe also compare the Device Tree of STM32MP157F-DK2 with the one you have.

Start from this https://github.com/STMicroelectronics/linux/blob/v6.1-stm32mp/arch/arm/boot/dts/stm32mp157f-dk2.dts, but look also at the includes.

Regards

[Khaled-ELGHA]

Hi @PatrickF,

Thank you so much for your reply and your support

I checked the same file in the other branch v5.15-stm32mp-r2.2 which is the corresponding file for my build which using kernel v5.15 :

openstlinux-5.15-yocto-kirkstone-mp1-v24.07.17

https://github.com/STMicroelectronics/linux/tree/v5.15-stm32mp-r2.2/arch/arm/boot/dts

I didn't find a specific difference related to my issue as I am including all the same files already and the .dts file is the one that I am editing for my custom board.

Kindly find attached the .dts file, and let me know if there is something that can help me, please

Thanks in advance!

[Khaled-ELGHA]

Hi @PatrickF,

I saw this commit:

drm/stm: dsi: expose DSI PHY internal clock

https://github.com/STMicroelectronics/linux/commit/efb5ffec359c61e9384c11227cc752afdae13365

It is applied only on Kernel v6.1 not to v5.15, I think this is the main issue. Now I was able to see the clock but I don't know why it is disabled. Do you have some idea or hints how to enable it or where to search to do that?

Thanks a lot