[U-Boot] problem with mpc837x start.S

[Scott Wood <scottwood@freescale.com>]

On 08/04/2011 06:37 AM, shawn Bai wrote:
> When enlarging Nor Flash to 4GiB, the AM in OR0 is 0x0000_0, where the number of zero is 17. 
> 
> According to what is said in datasheet, if the bit value of some bit in address mask is 0, 
> then the corresponding bit in address will be masked.
> 
> So, the higher 17 bits in address will be masked, is it right ?
> 
> If so, the range accessed in flash is just 32KBytes from the BA in BR0. 
> Is that right ? But Not the same with what you mean.

The address mask applies only to matching a chip select.  Once it's been
matched, the full address goes to the device -- minus the bits that the
device does not implement.  An bit whose address mask is zero is treated
the same as the least-significant 15 bits.

> And from what you replied before in this question, may I say the 32KBytes will repeat through 4GiB address space ? not 8MBytes ?

No.

> then, what is the effect of CONFIG_SYS_MONITOR_BASE in this ABSOLUTE branch as uboot comment indicates ?

The effect is that the program counter contains "CONFIG_SYS_MONITOR_BASE
+ in_flash", so that when the code later shrinks the chipselect it will
still be executing from flash.

-Scott