drivers: ieee802154: nrf: limit number of serialized calls

For serialized nRF IEEE 802.15.4 Driver host, avoid using
`nrf_802154_csl_writer_anchor_time_set` too often by caching the CSL
RX time and period and using them to detect any shift on the periodic
pattern.

This improves power consumption by limiting the number of serialized calls.

Signed-off-by: Eduardo Montoya <[email protected]>

Author: edmont

drivers/ieee802154/ieee802154_nrf5.c

@@ -65,6 +65,8 @@ static struct nrf5_802154_data nrf5_data;
 
 #define DRX_SLOT_RX 0 /* Delayed reception window ID */
 
+#define NSEC_PER_TEN_SYMBOLS (10 * IEEE802154_PHY_OQPSK_780_TO_2450MHZ_SYMBOL_PERIOD_NS)
+
 #if defined(CONFIG_IEEE802154_NRF5_UICR_EUI64_ENABLE)
 #if defined(CONFIG_SOC_NRF5340_CPUAPP)
 #if defined(CONFIG_TRUSTED_EXECUTION_NONSECURE)
@@ -925,8 +927,20 @@ static int nrf5_configure(const struct device *dev,
 
 #if defined(CONFIG_IEEE802154_CSL_ENDPOINT)
 	case IEEE802154_CONFIG_EXPECTED_RX_TIME: {
-		nrf_802154_csl_writer_anchor_time_set(nrf_802154_timestamp_phr_to_mhr_convert(
-			config->expected_rx_time / NSEC_PER_USEC));
+
+#if defined(CONFIG_NRF_802154_SER_HOST)
+		net_time_t period_ns = nrf5_data.csl_period * NSEC_PER_TEN_SYMBOLS;
+		bool changed = (config->csl_rx_time - nrf5_data.csl_rx_time) % period_ns;
+
+		nrf5_data.csl_rx_time = config->csl_rx_time;
+
+		if (changed)
+#endif /* CONFIG_NRF_802154_SER_HOST */
+		{
+			nrf_802154_csl_writer_anchor_time_set(
+				nrf_802154_timestamp_phr_to_mhr_convert(config->expected_rx_time /
+									NSEC_PER_USEC));
+		}
 	} break;
 
 	case IEEE802154_CONFIG_RX_SLOT: {
@@ -942,9 +956,12 @@ static int nrf5_configure(const struct device *dev,
 				      config->rx_slot.channel, DRX_SLOT_RX);
 	} break;
 
-	case IEEE802154_CONFIG_CSL_PERIOD:
+	case IEEE802154_CONFIG_CSL_PERIOD: {
 		nrf_802154_csl_writer_period_set(config->csl_period);
-		break;
+#if defined(CONFIG_NRF_802154_SER_HOST)
+		nrf5_data.csl_period = config->csl_period;
+#endif
+	} break;
 #endif /* CONFIG_IEEE802154_CSL_ENDPOINT */
 
 #if defined(CONFIG_IEEE802154_NRF5_MULTIPLE_CCA)

drivers/ieee802154/ieee802154_nrf5.h

@@ -92,6 +92,14 @@ struct nrf5_802154_data {
 	/* The maximum number of extra CCA attempts to be performed before transmission. */
 	uint8_t max_extra_cca_attempts;
 #endif
+
+#if defined(CONFIG_NRF_802154_SER_HOST) && defined(CONFIG_IEEE802154_CSL_ENDPOINT)
+	/* The last configured value of CSL period in units of 10 symbols. */
+	uint32_t csl_period;
+
+	/* The last configured value of CSL phase time in nanoseconds. */
+	net_time_t csl_rx_time;
+#endif /* CONFIG_NRF_802154_SER_HOST && CONFIG_IEEE802154_CSL_ENDPOINT */
 };
 
 #endif /* ZEPHYR_DRIVERS_IEEE802154_IEEE802154_NRF5_H_ */