[nrf fromlist] Bluetooth: Mesh: correction lpn rx delay

If extended advertiser is used, then advertiser sends callback
quite close to the real tx end time. No necessity to consider
advertisement time in lpn rx delay. It allows lpn to spend
less time in active scanning and save more power. Unfortunately,
legacy advertiser shows very slow precision. It is mandatory to
consider adv time for it. Additionally, unnecessary considering of
the advertisement duration has been removed for receive window in lpn.
It makes scanner window longer for a couple of milliseconds.
This is the responsibility of friend node to configure window that
it can manage.

Upstream PR: zephyrproject-rtos/zephyr#54679

Signed-off-by: Aleksandr Khromykh <[email protected]>

Author: alxelax

subsys/bluetooth/mesh/lpn.c

@@ -38,6 +38,12 @@ LOG_MODULE_REGISTER(bt_mesh_lpn);
 	 CONFIG_LOG_MODE_DEFERRED Kconfig option when Low Power node feature is enabled.
 #endif
 
+#if defined(CONFIG_BT_MESH_ADV_LEGACY)
+#define RX_DELAY_CORRECTION(lpn) ((lpn)->adv_duration)
+#else
+#define RX_DELAY_CORRECTION(lpn) 0
+#endif
+
 #if defined(CONFIG_BT_MESH_LPN_AUTO)
 #define LPN_AUTO_TIMEOUT (CONFIG_BT_MESH_LPN_AUTO_TIMEOUT * MSEC_PER_SEC)
 #else
@@ -414,8 +420,7 @@ static void req_send_end(int err, void *user_data)
 		 * response data due to HCI and other latencies.
 		 */
 		k_work_reschedule(&lpn->timer,
-				  K_MSEC(LPN_RECV_DELAY - SCAN_LATENCY -
-					 (int32_t)lpn->adv_duration));
+				  K_MSEC(LPN_RECV_DELAY - SCAN_LATENCY - RX_DELAY_CORRECTION(lpn)));
 	} else {
 		lpn_set_state(BT_MESH_LPN_WAIT_UPDATE);
 		k_work_reschedule(&lpn->timer, K_MSEC(LPN_RECV_DELAY + lpn->recv_win));
@@ -912,7 +917,7 @@ static void lpn_timeout(struct k_work *work)
 		break;
 	case BT_MESH_LPN_RECV_DELAY:
 		k_work_reschedule(&lpn->timer,
-				  K_MSEC(lpn->adv_duration + SCAN_LATENCY + lpn->recv_win));
+				  K_MSEC(SCAN_LATENCY + lpn->recv_win + RX_DELAY_CORRECTION(lpn)));
 		bt_mesh_scan_enable();
 		lpn_set_state(BT_MESH_LPN_WAIT_UPDATE);
 		break;