Preserve port configuration registers in DL_Down status.
ShawnLess opened this issue · 2 comments
In PCIe Spec 6.0, Chapter 2.9.1,
"For a Downstream Port, DL_Down status is handled by:
• Initializing back to their default state any buffers or internal states associated with outstanding requests transmitted Downstream
Port configuration registers must not be affected, except as required to update status associated with the transition to DL_Down."
Most of the implementation will "Initializing back to their default state" during DL_Down status, but ignores the "Port configuration registers must not be affected".
This leads to serious problem in hot-plug scenario, where the link related registers (max payload size, link width/size information) are lost after removing the device, and won't be able to recover after the devices is plugged back.
Wondering shall we specifically adding this rule.
Losing the port configurations is clearly violating the PCIe specification. However if you have observed this is violated some implementations then it makes sense to add a rule about this.