System hangs

When using the SB in combination with the FCPB, there's several cases that yield an unresponsive system which requires a SB reset:

1. addressing any peripheral slot which has no working Aurora c2c link (either card missing or c2c unresponsive)
2. after having a working SB <> FCPB link, reflashing the FCPB gateware followed by a c2c reset using c2c_service. I tried both with RST_N asserted and deasserted before reflashing with no avail.

The above cases are not related I think, and since they are not that exotic use cases a solution would be needed.

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Adding another case, slightly related:

3. after reflashing the FCPB, normally the led_0 comes up immediately i.e. Aurora channel_up. None of the resets seems to affect if, though it might be too short to see with the naked eye. Sometimes however the channel_up doesn't come up and when it doesn't, impossible to bring up the link with any reset combination, even after rebooting the SB. Only a full crate power cycle resolves this issue.. This might help the debugging: during that case, the c2c reset doesn't detect the PB in slot 3 (even after toggling BP RST_N). From my custom gateware, I can see though that the BP RST_n does work and propagate as expected.