OMAP L138 Writes to reserved memory writes on DDR address

Hi,

The OMAP L138 have the DDR mapped from 0xC000 0000 to 0xDFFF FFFF and next to it has a reserved zone, from 0xE000 0xFFFF FFFF.

Using devmem2 [1] it appears that any write to the reserved zone is mapped on ddr space.

For example,

root@arago:~# devmem2 0xE0000FF0
/dev/mem opened.
Memory mapped at address 0xb6f82000.
Read at address  0xE0000FF0 (0xb6f82ff0): 0xE3A0000B
root@arago:~# devmem2 0xC0000FF0
/dev/mem opened.
Memory mapped at address 0xb6fa1000.
Read at address  0xC0000FF0 (0xb6fa1ff0): 0xE3A0000B
root@arago:~# devmem2 0xC0000FF0 w 0x123
/dev/mem opened.
Memory mapped at address 0xb6f87000.
Read at address  0xC0000FF0 (0xb6f87ff0): 0xE3A0000B
Write at address 0xC0000FF0 (0xb6f87ff0): 0x00000123, readback 0x00000123
root@arago:~# devmem2 0xE0000FF0
/dev/mem opened.
Memory mapped at address 0xb6f08000.
Read at address  0xE0000FF0 (0xb6f08ff0): 0x00000123

The Memory Protection Unit don't offer any protection against this behavior, don't allow address so high but the write still goes to ddr, making memory corruption.

Any idea why we can block this behavior ?

Thanks.

Regards,
Aníbal