In the case where head == 0 on the circular buffer, there should be one
DMA buffer, not two. The second zero-length buffer would break the
lpuart driver, transfer would never complete.
Signed-off-by: Aaron Brice <aaron.brice@datasoft.com> Acked-by: Stefan Agner <stefan@agner.ch> Tested-by: Stefan Agner <stefan@agner.ch> Tested-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>