[QUESTION] TC 830 MSE bit functionnality

[f4bjh]

Hi,

I'm facing a TC failed on my platform : TC 830 Check Cmd Reg memory space enable on Root Port.

Could you, please, point the specification where it is stated that MSE bit of Root Port should disable access to MMIO space of a downstream device ?

Thanks in advance for your help

Regards,
Fabrice DECROP LONGET

[Sujana-M]

Hi @f4bjh

The PCIe specs states the below for MSE bit:

Memory Space Enable: Controls a Function's response to Memory Space accesses. When this bit is Clear, all received Memory Space accesses are caused to be handled as Unsupported Requests. When this bit is Set, the Function is enabled to decode the address and further process Memory Space accesses.

The memory accesses to a downstream port go through the Root port. Hence, any memory access to a downstream port of a RP, whose MSE bit is disabled will be handled as a UR response.

Thanks,
ACS Team