PROCESSOR-SDK-DRA7X: Want to understand some concepts of CMA

AllenHsu

Part Number: PROCESSOR-SDK-DRA7X

Our command line is "mem=1024M cma=64M", and the command line transfer from uboot to kernel.

Is this cma=64M included in mem=1024M ?

If not, where is the starting position of the CMA region?

0 Yordan Kamenov over 5 years ago

Hi,

please check if the following documents can help you:

<Kernel_dir>/Documentation/kernel-parameters.txt

<Kernel_dir>/Documentation/cma/debugfs.txt

<Kernel_dir>/drivers/base/dma-contiguous.c

<Kernel_dir>/include/linux/dma-contiguous.h

Regards,

Yordan

0 AllenHsu over 5 years ago in reply to Yordan Kamenov

Thank you for your information.

According to my tracking of dma-contiguous.c code,
The size of the cma (cma=64M) is obtained from Linux kernel,

So I infer that the space used by CMA is also from the memory of the kerenl (mem=1024M).

Is my inference above correct?

0 Yordan Kamenov over 5 years ago in reply to AllenHsu

Hi Allen,

your understanding is correct, it is part of mem=1024M.

Regards,

Yordan

Processors forum