ms: Add support for slot reservation

In contrast to the slots currently used by existing TBFs, the
reserved slots refer to the time slots that can be used for newly
allocated TBFs without causing conflicts (given that the first common
TS does not change). They correspond to the potential use of the
PDCHs and can be used to achieve a more uniform slot allocation.

This commit adds bit set based methods to GprsMs and gprs_rlcmac_trx
and a counter to gprs_rlcmac_pdch. The current TRX will also be
stored in the MS object.

Sponsored-by: On-Waves ehf

src/bts.cpp

@@ -1147,3 +1147,32 @@ void gprs_rlcmac_pdch::detach_tbf(gprs_rlcmac_tbf *tbf)
 	LOGP(DRLCMAC, LOGL_INFO, "PDCH(TS %d, TRX %d): Detaching %s, %d TBFs.\n",
 		ts_no, trx_no(), tbf->name(), m_num_tbfs[tbf->direction]);
 }
+
+void gprs_rlcmac_pdch::reserve(enum gprs_rlcmac_tbf_direction dir)
+{
+	m_num_reserved[dir] += 1;
+}
+
+void gprs_rlcmac_pdch::unreserve(enum gprs_rlcmac_tbf_direction dir)
+{
+	OSMO_ASSERT(m_num_reserved[dir] > 0);
+	m_num_reserved[dir] -= 1;
+}
+
+void gprs_rlcmac_trx::reserve_slots(enum gprs_rlcmac_tbf_direction dir,
+	uint8_t slots)
+{
+	unsigned i;
+	for (i = 0; i < ARRAY_SIZE(pdch); i += 1)
+		if (slots & (1 << i))
+			pdch[i].reserve(dir);
+}
+
+void gprs_rlcmac_trx::unreserve_slots(enum gprs_rlcmac_tbf_direction dir,
+	uint8_t slots)
+{
+	unsigned i;
+	for (i = 0; i < ARRAY_SIZE(pdch); i += 1)
+		if (slots & (1 << i))
+			pdch[i].unreserve(dir);
+}

src/bts.h

@@ -71,6 +71,10 @@ struct gprs_rlcmac_pdch {
 	void detach_tbf(gprs_rlcmac_tbf *tbf);
 
 	unsigned num_tbfs(enum gprs_rlcmac_tbf_direction dir) const;
+
+	void reserve(enum gprs_rlcmac_tbf_direction dir);
+	void unreserve(enum gprs_rlcmac_tbf_direction dir);
+	unsigned num_reserved(enum gprs_rlcmac_tbf_direction dir) const;
 #endif
 
 	uint8_t m_is_enabled; /* TS is enabled */
@@ -100,6 +104,7 @@ private:
 #endif
 
 	uint8_t m_num_tbfs[2];
+	uint8_t m_num_reserved[2];
 };
 
 struct gprs_rlcmac_trx {
@@ -112,6 +117,11 @@ struct gprs_rlcmac_trx {
 	/* back pointers */
 	struct BTS *bts;
 	uint8_t trx_no;
+
+#ifdef __cplusplus
+	void reserve_slots(enum gprs_rlcmac_tbf_direction dir, uint8_t slots);
+	void unreserve_slots(enum gprs_rlcmac_tbf_direction dir, uint8_t slots);
+#endif
 };
 
 /**
@@ -311,6 +321,12 @@ inline unsigned gprs_rlcmac_pdch::num_tbfs(enum gprs_rlcmac_tbf_direction dir) c
 	return m_num_tbfs[dir];
 }
 
+inline unsigned gprs_rlcmac_pdch::num_reserved(
+	enum gprs_rlcmac_tbf_direction dir) const
+{
+	return gprs_rlcmac_pdch::m_num_reserved[dir];
+}
+
 inline struct rate_ctr_group *BTS::rate_counters() const
 {
 	return m_ratectrs;

src/gprs_ms.cpp

@@ -91,7 +91,10 @@ GprsMs::GprsMs(BTS *bts, uint32_t tlli) :
 	m_ref(0),
 	m_list(this),
 	m_delay(0),
-	m_nack_rate_dl(0)
+	m_nack_rate_dl(0),
+	m_reserved_dl_slots(0),
+	m_reserved_ul_slots(0),
+	m_current_trx(NULL)
 {
 	LOGP(DRLCMAC, LOGL_INFO, "Creating MS object, TLLI = 0x%08x\n", tlli);
 
@@ -115,6 +118,8 @@ GprsMs::~GprsMs()
 {
 	LOGP(DRLCMAC, LOGL_INFO, "Destroying MS object, TLLI = 0x%08x\n", tlli());
 
+	set_reserved_slots(NULL, 0, 0);
+
 	if (osmo_timer_pending(&m_timer))
 		osmo_timer_del(&m_timer);
 
@@ -240,8 +245,12 @@ void GprsMs::detach_tbf(gprs_rlcmac_tbf *tbf)
 	if (tbf->ms() == this)
 		tbf->set_ms(NULL);
 
-	if (!m_dl_tbf && !m_ul_tbf && tlli() != 0)
-		start_timer();
+	if (!m_dl_tbf && !m_ul_tbf) {
+		set_reserved_slots(NULL, 0, 0);
+
+		if (tlli() != 0)
+			start_timer();
+	}
 
 	update_status();
 }
@@ -529,6 +538,28 @@ int GprsMs::first_common_ts() const
 	return -1;
 }
 
+void GprsMs::set_reserved_slots(gprs_rlcmac_trx *trx,
+	uint8_t ul_slots, uint8_t dl_slots)
+{
+	if (m_current_trx) {
+		m_current_trx->unreserve_slots(GPRS_RLCMAC_DL_TBF,
+			m_reserved_dl_slots);
+		m_current_trx->unreserve_slots(GPRS_RLCMAC_UL_TBF,
+			m_reserved_ul_slots);
+		m_reserved_dl_slots = 0;
+		m_reserved_ul_slots = 0;
+	}
+	m_current_trx = trx;
+	if (trx) {
+		m_reserved_dl_slots = dl_slots;
+		m_reserved_ul_slots = ul_slots;
+		m_current_trx->reserve_slots(GPRS_RLCMAC_DL_TBF,
+			m_reserved_dl_slots);
+		m_current_trx->reserve_slots(GPRS_RLCMAC_UL_TBF,
+			m_reserved_ul_slots);
+	}
+}
+
 gprs_rlcmac_tbf *GprsMs::tbf(enum gprs_rlcmac_tbf_direction dir) const
 {
 	switch (dir) {

src/gprs_ms.h

@@ -37,6 +37,7 @@ extern "C" {
 #include <stddef.h>
 
 struct BTS;
+struct gprs_rlcmac_trx;
 
 class GprsMs {
 public:
@@ -79,6 +80,11 @@ public:
 	uint8_t current_cs_dl() const;
 
 	int first_common_ts() const;
+	uint8_t reserved_dl_slots() const;
+	uint8_t reserved_ul_slots() const;
+	gprs_rlcmac_trx *current_trx() const;
+	void set_reserved_slots(gprs_rlcmac_trx *trx,
+		uint8_t ul_slots, uint8_t dl_slots);
 
 	gprs_llc_queue *llc_queue();
 	const gprs_llc_queue *llc_queue() const;
@@ -144,6 +150,9 @@ private:
 
 	pcu_l1_meas m_l1_meas;
 	unsigned m_nack_rate_dl;
+	uint8_t m_reserved_dl_slots;
+	uint8_t m_reserved_ul_slots;
+	gprs_rlcmac_trx *m_current_trx;
 };
 
 inline uint32_t GprsMs::tlli() const
@@ -199,3 +208,17 @@ inline unsigned GprsMs::nack_rate_dl() const
 	return m_nack_rate_dl;
 }
 
+inline uint8_t GprsMs::reserved_dl_slots() const
+{
+	return m_reserved_dl_slots;
+}
+
+inline uint8_t GprsMs::reserved_ul_slots() const
+{
+	return m_reserved_ul_slots;
+}
+
+inline gprs_rlcmac_trx *GprsMs::current_trx() const
+{
+	return m_current_trx;
+}