# Early UART setup on 2.6 kernel for mpc85xx

- From: mike zheng \<hidden\>
- Date: 2007-08-11 01:43:43 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2007/08/9424938
- Thread: https://ratatoskr.run/linuxppc-dev/2007/08/9424938/t.md

```text
Hi All,

In order to debug the kernel 2.6, I want setup serial port with UART on
mpc85xx as early as possible. I add the register access code at the
beginning of  platform_init(). For example, I try to write THR
register(0xe0004500). However the system just hanging there with this line.
If I comment out this line, everything works fine.

Here is the code my mpc85xx_cds_common.c:

void __init
platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
                   unsigned long r6, unsigned long r7)
{

....
}
```