i.MX6SX UART clock during uboot

[torus1000]

Hi,

I tested UART of i.MX6SX then I found UART clock switched from OSC to PLL3 during boot up of linux.

It caused error/unexpected data feeding on UART which assigned to Cortex-M4 in our case.

Why UART clock changed from OSC @uboot to PLL3 @linux?

Is there any way to supply PLL3 clock to UART from the beginning?

Can anyone help me?

[Carlos_Musich · Accepted solution]

Hi torus,

when Linux starts it takes all the hardware configurations from the device tree, so if the device tree has a different configurations from uboot it will change. Of you want to keep the same configuration you must edit the device tree. Here you will find UART node and you can set the clock here. As this is a quite extensive topic I can provide you with some useful links.

Definitive GPIO guide - Studio Kousagi Wiki 

Device Tree Tutorial (ARM) | Linux Kernel For Newbies 

Device Tree Made Easy 

https://events.linuxfoundation.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf 

Regards,
Carlos

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[torus1000]

Dear Carlos, @Carlos_Musich

Just in case, I would like to confirm about my guess that there is no particular reason to choose PLL3.

Is it correct?

BR