nvme: fix PCIe subsystem reset controller state transition

The commit d2fe192 (“nvme: only allow entering LIVE from CONNECTING
state”) disallows controller state transitions directly from RESETTING
to LIVE. However, the NVMe PCIe subsystem reset path relies on this
transition to recover the controller on PowerPC (PPC) systems.

On PPC systems, issuing a subsystem reset causes a temporary loss of
communication with the NVMe adapter. A subsequent PCIe MMIO read then
triggers EEH recovery, which restores the PCIe link and brings the
controller back online. For EEH recovery to proceed correctly, the
controller must transition back to the LIVE state.

Due to the changes introduced by commit d2fe192 (“nvme: only allow
entering LIVE from CONNECTING state”), the controller can no longer
transition directly from RESETTING to LIVE. As a result, EEH recovery
exits prematurely, leaving the controller stuck in the RESETTING state.

Fix this by explicitly transitioning the controller state from RESETTING
to CONNECTING and then to LIVE. This satisfies the updated state
transition rules and allows the controller to be successfully recovered
on PPC systems following a PCIe subsystem reset.

Cc: stable@vger.kernel.org
Fixes: d2fe192 ("nvme: only allow entering LIVE from CONNECTING state")
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: shroffni

drivers/nvme/host/pci.c

@@ -1532,7 +1532,10 @@ static int nvme_pci_subsystem_reset(struct nvme_ctrl *ctrl)
 	}
 
 	writel(NVME_SUBSYS_RESET, dev->bar + NVME_REG_NSSR);
-	nvme_change_ctrl_state(ctrl, NVME_CTRL_LIVE);
+
+	if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_CONNECTING) ||
+	    !nvme_change_ctrl_state(ctrl, NVME_CTRL_LIVE))
+		goto unlock;
 
 	/*
 	 * Read controller status to flush the previous write and trigger a