topic Re: How do you disable caching and the interrupt controller on a i.MX6? in i.MX Processors

How do you disable caching and the interrupt controller on a i.MX6?

briannorman — Mon, 03 Feb 2014 21:52:12 GMT

I am having difficulties passing execution from on kernel to another. I'm using Green Hills Integrity and their documentation states that i need to disable all cache and disable interrupt controller before i can run the newly loaded kernel. Unfortunately, I'm having a hard time finding any documentation on how to do this in the cortex A9. Any body have any ideas on how to do this or where i can find some documentation?

Re: How do you disable caching and the interrupt controller on a i.MX6?

EricNelson — Mon, 03 Feb 2014 22:15:29 GMT

Hi Brian,

Are you using U-Boot to load the image? If so, main-line U-Boot contains a command "dcache off" that you can use to disable the cache before launching Integrity.

Re: How do you disable caching and the interrupt controller on a i.MX6?

briannorman — Mon, 03 Feb 2014 22:43:50 GMT

yes and no. There is a lot of setup i haven't been able to figure out in Integrity yet so i initially boot with U-boot. With U-boot i am able to bootm my kernels just fine. The problem that i have is i need a more intelligent boot program that can do more that u-boot so I'm trying to use an Integrity bootloader. I can load and start if from u-boot just fine. Then, using the Integrity bootloader, i want to load and run my application. According to the console output, my application is decompressing correctly and i get a message that the new kernel is booting, but then it hangs. According to Green Hills documentation, i need to disable cache and interrupts before i jump to the new kernel, using a BSP function that i need to write. I have wrote the function and i see that it is called, but i don't know how it is supposed to disable cache and interrupts.

Maybe i need to dive into u-boot code again and see what "dcache off" does. Is there a U-boot command to disable the interrupt handler?

BTW, thanks for your response. Any way you can help would be greatly appreciated, I've been beating my head against this for a couple weeks now.

Re: How do you disable caching and the interrupt controller on a i.MX6?

EricNelson — Tue, 04 Feb 2014 00:46:12 GMT

Hi Brian,

The basic cache maintenance code in U-Boot is here:

https://github.com/boundarydevices/u-boot-imx6/blob/production/arch/arm/cpu/armv7/cache_v7.c

Also see cache*.c in arch/arm/lib:

https://github.com/boundarydevices/u-boot-imx6/tree/production/arch/arm/lib