[U-Boot-Users] Zilog Z85230 serial communication controller

["Häpe, Sebastian, HRD/AB"]

Hi again!

Currently I try to integrate a Zilog Z85230 serial communication controller
on a 603e-based board to work with U-Boot.
For testing reasons I wrote a little inline assembler program looking like
that:


#include <common.h>

#ifdef CFG_Z85230

#if CONFIG_CONS_INDEX == 1
#else
#error no valid console defined
#endif

int serial_init (void)
{

	/* First we load the _physical_ address of the chip's cntrol
register to R3 */
	__asm__ __volatile__ ("addis 3, 0, 0x0000");
	__asm__ __volatile__ ("addis 3,0,0xF500");
	__asm__ __volatile__ ("ori 3,3,0x00D0");
	
	/* Load the address of the chip's data rgister to R2 */
	  __asm__ __volatile__ ("addis 2, 0, 0x0000");
        __asm__ __volatile__ ("addis 2,0,0xF500");
        __asm__ __volatile__ ("ori 2,2,0x00D8");

	
      /* Here some configuration for the serial controller is done, use R4
*/
	__asm__ __volatile__ ("li 4, 0x04");
	__asm__ __volatile__ ("stb 4, 0(3)");
	__asm__ __volatile__ ("li 4, 0x44");
	__asm__ __volatile__ ("stb 4, 0(3)");

	.
	.
	.
	.

	/* Write one character ('I') */
	__asm__ __volatile__ ("addis 4, 0, 0x0000");
	__asm__ __volatile__ ("li 4, 0x49");
	__asm__ __volatile__ ("stb 4, 0(2)");

	return(0);
}
.
.
.

When I compile this, load it into RAM and execute it, everything is fine,
MiniCom shows an 'I'.
Now I put this litte function into the file serial.c from U-Boot and compile
it.
Then I load U-Boot to Flash and run it. I'm tested before, wheather the
function is always called and it is.

When I run it, I get an error, caused by the MMU, because it cannot
translate the demanded address (it's a physical one).
Now I tried to disable the data-address-translation on the beginning of the
function and re-enable it at the end, always surrounded by an
'isync'-command. It this case, the program runs, but without any output via
the serial port.

Is it legal to disable the MMU in this context and how should I configure
U-Boot for my memory map? 

I have the following memory map on my board:

0x00000000 - 0x007FEFFF SRAM

0xF5000000 - Serial Interface #1 Channel B Control
0xF5000008 - Serial Interface #1 Channel B Data
.
.
.
0xF50000D0 - Serial Interface #3 Channel A Control
0xF50000D8 - Serial Interface #3 Channel A Data

0xFF800000 - 0xFFFFFFFF Flash

Thanks for ideas or advices why this doesn't work? 

Sebastian Häpe