On Tue, 5 Aug 2014 12:55:33 -0400 TR Reardon thomas_reardon@hotmail.com wrote:
I tried looking for an answer to this but a quick one didn't surface: when flash regions are protected, is this implemented by the flash chip itself or by the SPI logic (ie ichspi for Intel programmer)?
Both, and more. There are 3 common cases:
1) was used at least in the last 20 years or so: a GPIO line from the chipset is connected to the write protection pin (most flash chips have that). This is usually mainboard-specific and is handled by flashrom in board_enable.c
2) Some flash chips offer software locking mechanisms where some commands need to be sent to the flash chip to lock and unlock respective address ranges. Those settings can then also be hardward-locked via 1)
3) are programmer-based protections such those seen on Intel chipsets where the chipset hardware implements a kind of firewall for the SPI stream.