tbf_dl: Clarify requirements for DL ACK/NACK

Method is renamed since it clearly relates to getting DL ACK/NACK, no
CTRL ACK.

use same methods in both scheduler and internal use since they are
expectd to be run in the same code path by the scheduler. This way we
make sure the same conditions apply and it's clearer when looking at
the code.

Change-Id: Ib0e9b9547f5292b95064bab2dc182fdf659f0518

src/gprs_rlcmac_sched.cpp

@@ -239,7 +239,7 @@ static inline enum tbf_dl_prio tbf_compute_priority(const struct gprs_rlcmac_bts
 	int age_thresh1 = msecs_to_frames(200);
 	int age_thresh2 = msecs_to_frames(OSMO_MIN(msecs_t3190/2, dl_tbf_idle_msec));
 
-	if (tbf->is_control_ts(ts) && tbf->need_control_ts())
+	if (tbf->is_control_ts(ts) && tbf->need_poll_for_dl_ack_nack())
 		return DL_PRIO_CONTROL;
 
 	if (tbf->is_control_ts(ts) && age > age_thresh2 && age_thresh2 > 0)

src/tbf_dl.cpp

@@ -779,7 +779,6 @@ struct msgb *gprs_rlcmac_dl_tbf::create_dl_acked_block(
 	uint8_t *msg_data;
 	struct msgb *dl_msg;
 	unsigned msg_len;
-	bool need_poll;
 	/* TODO: support MCS-7 - MCS-9, where data_block_idx can be 1 */
 	uint8_t data_block_idx = 0;
 	unsigned int rrbp;
@@ -940,23 +939,20 @@ struct msgb *gprs_rlcmac_dl_tbf::create_dl_acked_block(
 	if (m_last_dl_poll_fn < 0)
 		m_last_dl_poll_fn = fn;
 
-	need_poll = state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK);
-
-	/* poll after POLL_ACK_AFTER_FRAMES frames, or when final block is tx.
-	 */
-	if (m_tx_counter >= POLL_ACK_AFTER_FRAMES || m_dl_ack_requested ||
-			need_poll) {
+	/* poll after POLL_ACK_AFTER_FRAMES frames, or when final block is tx or
+	 * when last polled DL ACK/NACK was lost. */
+	if (need_poll_for_dl_ack_nack()) {
 		if (m_dl_ack_requested) {
 			LOGPTBFDL(this, LOGL_DEBUG,
 				  "Scheduling Ack/Nack polling, because it was requested explicitly "
 				  "(e.g. first final block sent).\n");
-		} else if (need_poll) {
+		} else if (state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK)) {
 			LOGPTBFDL(this, LOGL_DEBUG,
 				  "Scheduling Ack/Nack polling, because polling timed out.\n");
 		} else {
 			LOGPTBFDL(this, LOGL_DEBUG,
 				  "Scheduling Ack/Nack polling, because %d blocks sent.\n",
-				POLL_ACK_AFTER_FRAMES);
+				  POLL_ACK_AFTER_FRAMES);
 		}
 
 		rc = check_polling(fn, ts, &new_poll_fn, &rrbp);
@@ -1211,8 +1207,11 @@ void gprs_rlcmac_dl_tbf::request_dl_ack()
 	m_dl_ack_requested = true;
 }
 
-bool gprs_rlcmac_dl_tbf::need_control_ts() const
+/* Does this DL TBF require to poll the MS for DL ACK/NACK? */
+bool gprs_rlcmac_dl_tbf::need_poll_for_dl_ack_nack() const
 {
+	/* poll after POLL_ACK_AFTER_FRAMES frames, or when final block is tx or
+	 * when last polled DL ACK/NACK was lost. */
 	return state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK) ||
 		m_tx_counter >= POLL_ACK_AFTER_FRAMES ||
 		m_dl_ack_requested;

src/tbf_dl.h

@@ -53,7 +53,7 @@ struct gprs_rlcmac_dl_tbf : public gprs_rlcmac_tbf {
 	void trigger_ass(struct gprs_rlcmac_tbf *old_tbf);
 
 	void request_dl_ack();
-	bool need_control_ts() const;
+	bool need_poll_for_dl_ack_nack() const;
 	bool have_data() const;
 	int frames_since_last_poll(unsigned fn) const;
 	int frames_since_last_drain(unsigned fn) const;