MontaVista 4 GPIO

Shijia Guo

Hi all,

I'm using MontaVista 4 for my DM6446 development. I defined the GPIO base in my code:

include/asm-arm/arch-davinci/hardware.h: #define DAVINCI_GPIO_BASE (0x01C67000)

However, for whatever reason, when I built the kernel, loaded it to my board and ran the kernel, the GPIO base showed as 0xe1067000. The way I checked this GPIO is by:

$ cat /proc/gio/registers

All other GPIO address are with the correct offset. I'm curious why the BASE address is shifted. Appreciate any help!

over 12 years ago

0 Diego Santa Cruz over 12 years ago

Intellectual 360 points

Hi,

The Linux kernel uses virtual addresses for most things and not physical addresses. The DM6446 kernel basically maps all of the device IO space at a virtual address.

I would strongly suggest that you get a copy of the Linux Device Drivers book to understand the kernel for writing device drivers. It is a bit outdated, but it actually matches the MV Pro 4 kernel version, which BTW is very old and no longer maintained as far as I know.

Best,

Diego

0 Shijia Guo over 12 years ago in reply to Diego Santa Cruz

Prodigy 180 points

Thank you very much! It is valuable information.

Processors

Processors forum

MontaVista 4 GPIO