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PNP: Do not disable devices on suspend when they cannot be re-enabled on resume
On an Advantech MICA-071 tablet, with a builtin barcode scanner connected
to ttyS0, the following message is shown on suspend:
serial 00:02: disabled
And after suspend/resume trying to use the barcode scanner / ttyS0 shows:
serial 00:02: LSR safety check engaged!
Indicating that the UARTs io-ports are no longer reachable.
This is caused by __pnp_bus_suspend() calling pnp_stop_dev() on the "00:02"
pnp device on suspend (this outputs the disabled message).
The problem is that pnp_can_write() returns false for the "00:02" pnp
device, so after disabling it (disabling its decoding of IO addresses)
during suspend, it cannot be re-enabled.
Add a pnp_can_write() check to the suspend path and only disable devices
which can actually be re-enabled on resume.
This fixes the Advantech MICA-071's ttyS0 no longer working after
a suspend/resume.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>