This allows DMA engine to go into runtime-suspended mode whenever there is
no data to receive, instead of keeping DMA active all the time while TTY
is opened (i.e. permanently active in practice, like in the case of UART
Bluetooth).
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200112180919.5194-2-digetx@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>