From: Chen, Jiqian <Jiqian.Chen@amd.com>
Sent: Wednesday, September 20, 2023 12:03 PM
If driver write 0 to reset device, can the SUSPEND bit be cleared?
It must as reset operation, resets everything else and so the suspend too.
(pci_pm_resume->virtio_pci_restore->virtio_device_restore-
virtio_reset_device)
If SUSPEND is cleared, then during the reset process in Qemu, I can't judge if
the reset request is from guest restore process or not, and then I can't change
the reset behavior.
Reset should not be influenced by suspend.
Suspend should do the work of suspend and reset to do the reset.
The problem to overcome in [1] is, resume operation needs to be synchronous as
it involves large part of context to resume back, and hence just asynchronously
setting DRIVER_OK is not enough.
The sw must verify back that device has resumed the operation and ready to
answer requests.
This is slightly different flow than setting the DRIVER_OK for the first time
device initialization sequence as it does not involve large restoration.
So, to merge two ideas, instead of doing DRIVER_OK to resume, the driver should
clear the SUSPEND bit and verify that it is out of SUSPEND.
Because driver is still in _OK_ driving the device flipping the SUSPEND bit.