skiboot 5.9.4 was released on Wednesday November 29th, 2017. It replaces skiboot-5.9.3 as the current stable release in the 5.9.x series.
Over skiboot-5.9.3, we have one NPU2/NVLink2 fix that works around a potential glitch (the one skiboot-5.9.3 would hard crash on rather than let a system continue to run until it mysteriously crashed later on).
That fix is in two parts:
npu2: hw-procedures: Change phy_rx_clock_sel values to recover from a potential glitch.
npu2: hw-procedures: Manipulate IOVALID during training
Ensure that the IOVALID bit for this brick is raised at the start of link training, in the reset_ntl procedure.
Then, to protect us from a glitch when the PHY clock turns off or gets chopped, lower IOVALID for the duration of the phy_reset and phy_rx_dccal procedures.