NIOS V/g - peripherals under 2GB Peripheral Region

Hi dim1​ 

KDB recommends to have non-cacheable peripheral regions above the 2GB address

This statement is incorrect. (However, we agree that the KDB needs better clarity, and it will be improved soon.)
The KDB is referring to the remaining Size available. Not the Base Address.

Excluding 2GB, Nios V/g processor still offers from 64KB to 1GB, or None.

In short, the issue is affecting Peripheral Regions that is configured with 2GB Size, regardless of the Base Address.
Take 4 designs as examples,

• Design 1
• 0x0 to 0xFFFF in 64KB Peripheral Region A will bypass cache.
• 0x4000_0000 to 0x7FFF_FFFF in 1GB Peripheral Region B will bypass cache.

• Design 2
• 0x0 to 0x7FFF_FFFF in 2GB Peripheral Region A will NOT bypass cache. 2GB Size is bugged.
• 0x8000_0000 to 0xBFFF_FFFF in 1GB Peripheral Region B will bypass cache.

• Design 3
• 0x4000_0000 to 0x7FFF_FFFF in 1GB Peripheral Region B will bypass cache.
• 0x8000_0000 to 0xFFFF_FFFF in 2GB Peripheral Region B will NOT bypass cache. 2GB Size is bugged.

• Design 4
• 0x0 to 0x7FFF_FFFF in 2GB Peripheral Region A will NOT bypass cache. 2GB Size is bugged.
• 0x8000_0000 to 0xFFFF_FFFF in 2GB Peripheral Region B will NOT bypass cache. 2GB Size is bugged.

Regards,
Liang Yu