net: openthread: Add support for HW CSMA CA

Forward CSMA CA capability to OpenThread and use CSMA CA enabled
transfer if supported.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

subsys/net/lib/openthread/platform/radio.c

@@ -189,9 +189,18 @@ void platformRadioProcess(otInstance *aInstance)
 		radio_api->set_txpower(radio_dev, tx_power);
 
 		if (sTransmitFrame.mInfo.mTxInfo.mCsmaCaEnabled) {
-			if (radio_api->cca(radio_dev) ||
-			    radio_api->tx(radio_dev, IEEE802154_TX_MODE_DIRECT,
-					  tx_pkt, tx_payload)) {
+			if (radio_api->get_capabilities(radio_dev) &
+			    IEEE802154_HW_CSMA) {
+				if (radio_api->tx(radio_dev,
+						  IEEE802154_TX_MODE_CSMA_CA,
+						  tx_pkt, tx_payload) != 0) {
+					result =
+					    OT_ERROR_CHANNEL_ACCESS_FAILURE;
+				}
+			} else if (radio_api->cca(radio_dev) != 0 ||
+				   radio_api->tx(radio_dev,
+						 IEEE802154_TX_MODE_DIRECT,
+						 tx_pkt, tx_payload) != 0) {
 				result = OT_ERROR_CHANNEL_ACCESS_FAILURE;
 			}
 		} else {
@@ -422,6 +431,11 @@ otRadioCaps otPlatRadioGetCaps(otInstance *aInstance)
 		caps |= OT_RADIO_CAPS_ENERGY_SCAN;
 	}
 
+	if (radio_caps & IEEE802154_HW_CSMA) {
+		caps |= OT_RADIO_CAPS_CSMA_BACKOFF |
+			OT_RADIO_CAPS_TRANSMIT_RETRIES;
+	}
+
 	return caps;
 }