We need to ensure the hardware is powered when we transmit a packet.
But if it's not, we can't block to wait for it. So asynchronously
request power in ipa_start_xmit(), and only proceed if the return
value indicates the power state is active.
If the hardware is not active, a runtime resume request will have
been initiated. In that case, stop the network stack from further
transmit attempts until the resume completes. Return NETDEV_TX_BUSY,
to retry sending the packet once the queue is restarted.
If the power request returns an error (other than -EINPROGRESS,
which just means a resume requested elsewhere isn't complete), just
drop the packet.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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