[U-Boot] Address Space in Uboot MPC85xx

[Kumar Gala]

On Nov 18, 2008, at 6:14 AM, Vignesh Kumar B wrote:

>
> Hi,
>
> I am going through the u-boot code for MPC85xx while I see some code  
> as
> follows.
> So what is this AS (Address Space) required and what does it do?  
> What is
> happening when we switch from AS=1 to AS=0.
>
> Can someone explain me what is going on?
>
> /* create a temp mapping in AS=1 to the boot window */
> 	lis     r6,FSL_BOOKE_MAS0(1, 15, 0)@h
> 	ori     r6,r6,FSL_BOOKE_MAS0(1, 15, 0)@l
> 	.
> 	.
> 	.
> 	.
>
> /* create a temp mapping in AS=1 to the stack */
> 	lis     r6,FSL_BOOKE_MAS0(1, 14, 0)@h
> 	ori     r6,r6,FSL_BOOKE_MAS0(1, 14, 0)@l
> 	.
> 	.
> 	.
> 	.
> /* switch back to AS = 0 */
> 	lis	r3,(MSR_CE|MSR_ME|MSR_DE)@h
> 	ori	r3,r3,(MSR_CE|MSR_ME|MSR_DE)@l

we switch address spaces to ensure that the TLBs we are going to use  
temporarily will not conflict.

- k