topic Re: LS1046A DMA Memory Access Issue in Layerscape

LS1046A DMA Memory Access Issue

JSKIM — Mon, 23 Nov 2020 13:49:27 GMT

I use LSDK2004, and dma api functions.

i use dma_alloc_coherent to alloc dma memory, and i check physical address of /proc/iomap which is 32bit address.

when i access to dma physical address at user space, there is access limit of dma memory.

But in case of kernel access such as ioctl, there is no problem.

May i have the reason?

yipingwang — Tue, 01 Dec 2020 08:38:24 GMT

How are you using this physical address when you see this limitation ?

Does this limitation also happen while accessing mmap'ed memory ?

JSKIM — Wed, 02 Dec 2020 01:08:02 GMT

I solved the issue.

In case of LSDK2004, there is access limit from user space to kernel memory when arch is ppc, x86, arm64.

So I changed the Kconfig of kernel.

JSKIM — Wed, 09 Dec 2020 00:59:48 GMT

I usually use devmem tool. and

i found there was access limit when i use mmap memory on kernel