at86rf230: add recommended csma backoffs settings

This patch adds support for a new random csma backoffs settings when
going into sleep state. This is recommended according at86rf2xx
datasheets.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
index b839bbd4ff69..7e30a45718c9 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -945,10 +945,21 @@ static void
 at86rf230_stop(struct ieee802154_hw *hw)
 {
         struct at86rf230_local *lp = hw->priv;
+        u8 csma_seed[2];
 
         at86rf230_sync_state_change(hw->priv, STATE_FORCE_TRX_OFF);
 
         disable_irq(lp->spi->irq);
+
+        /* It's recommended to set random new csma_seeds before sleep state.
+         * Makes only sense in the stop callback, not doing this inside of
+         * at86rf230_sleep, this is also used when we don't transmit afterwards
+         * when calling start callback again.
+         */
+        get_random_bytes(csma_seed, ARRAY_SIZE(csma_seed));
+        at86rf230_write_subreg(lp, SR_CSMA_SEED_0, csma_seed[0]);
+        at86rf230_write_subreg(lp, SR_CSMA_SEED_1, csma_seed[1]);
+
         at86rf230_sleep(lp);
 }