The SPI module can operate in all sleep modes by setting the run_in_standby option in the spi_config struct. The operation in slave and master mode is shown in the table below.
run_in_standby
Slave
Master
false
Disabled, all reception is dropped
GCLK is disabled when master is idle, wake on transmit complete
true
Wake on reception
GCLK is enabled while in sleep modes, wake on all interrupts