cxgb4/cxgb4vf: Use new interfaces to calculate BAR2 SGE Queue Register addresses

Use BAR2 Going To Sleep (GTS) for T5 and later. Use new BAR2 User Doorbells for
T5 for both cxgb4 and cxgb4vf driver.

Based on original work by Casey Leedom <leedom@chelsio.com>
Signed-off-by: NHariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cxgb4.h

@@ -438,7 +438,8 @@ struct sge_fl {                     /* SGE free-buffer queue state */
 	struct rx_sw_desc *sdesc;   /* address of SW Rx descriptor ring */
 	__be64 *desc;               /* address of HW Rx descriptor ring */
 	dma_addr_t addr;            /* bus address of HW ring start */
-	u64 udb;                    /* BAR2 offset of User Doorbell area */
+	void __iomem *bar2_addr;    /* address of BAR2 Queue registers */
+	unsigned int bar2_qid;      /* Queue ID for BAR2 Queue registers */
 };
 
 /* A packet gather list */
@@ -468,7 +469,8 @@ struct sge_rspq {                   /* state for an SGE response queue */
 	u16 abs_id;                 /* absolute SGE id for the response q */
 	__be64 *desc;               /* address of HW response ring */
 	dma_addr_t phys_addr;       /* physical address of the ring */
-	u64 udb;                    /* BAR2 offset of User Doorbell area */
+	void __iomem *bar2_addr;    /* address of BAR2 Queue registers */
+	unsigned int bar2_qid;      /* Queue ID for BAR2 Queue registers */
 	unsigned int iqe_len;       /* entry size */
 	unsigned int size;          /* capacity of response queue */
 	struct adapter *adap;
@@ -526,7 +528,8 @@ struct sge_txq {
 	int db_disabled;
 	unsigned short db_pidx;
 	unsigned short db_pidx_inc;
-	u64 udb;                    /* BAR2 offset of User Doorbell area */
+	void __iomem *bar2_addr;    /* address of BAR2 Queue registers */
+	unsigned int bar2_qid;      /* Queue ID for BAR2 Queue registers */
 };
 
 struct sge_eth_txq {                /* state for an SGE Ethernet Tx queue */

drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c

@@ -3805,6 +3805,22 @@ u64 cxgb4_read_sge_timestamp(struct net_device *dev)
 }
 EXPORT_SYMBOL(cxgb4_read_sge_timestamp);
 
+int cxgb4_bar2_sge_qregs(struct net_device *dev,
+			 unsigned int qid,
+			 enum cxgb4_bar2_qtype qtype,
+			 u64 *pbar2_qoffset,
+			 unsigned int *pbar2_qid)
+{
+	return t4_bar2_sge_qregs(netdev2adap(dev),
+				 qid,
+				 (qtype == CXGB4_BAR2_QTYPE_EGRESS
+				  ? T4_BAR2_QTYPE_EGRESS
+				  : T4_BAR2_QTYPE_INGRESS),
+				 pbar2_qoffset,
+				 pbar2_qid);
+}
+EXPORT_SYMBOL(cxgb4_bar2_sge_qregs);
+
 static struct pci_driver cxgb4_driver;
 
 static void check_neigh_update(struct neighbour *neigh)
@@ -3987,31 +4003,18 @@ static void process_db_drop(struct work_struct *work)
 		u32 dropped_db = t4_read_reg(adap, 0x010ac);
 		u16 qid = (dropped_db >> 15) & 0x1ffff;
 		u16 pidx_inc = dropped_db & 0x1fff;
-		unsigned int s_qpp;
-		unsigned short udb_density;
-		unsigned long qpshift;
-		int page;
-		u32 udb;
-
-		dev_warn(adap->pdev_dev,
-			 "Dropped DB 0x%x qid %d bar2 %d coalesce %d pidx %d\n",
-			 dropped_db, qid,
-			 (dropped_db >> 14) & 1,
-			 (dropped_db >> 13) & 1,
-			 pidx_inc);
-
-		drain_db_fifo(adap, 1);
+		u64 bar2_qoffset;
+		unsigned int bar2_qid;
+		int ret;
 
-		s_qpp = QUEUESPERPAGEPF1 * adap->fn;
-		udb_density = 1 << QUEUESPERPAGEPF0_GET(t4_read_reg(adap,
-				SGE_EGRESS_QUEUES_PER_PAGE_PF) >> s_qpp);
-		qpshift = PAGE_SHIFT - ilog2(udb_density);
-		udb = qid << qpshift;
-		udb &= PAGE_MASK;
-		page = udb / PAGE_SIZE;
-		udb += (qid - (page * udb_density)) * 128;
-
-		writel(PIDX(pidx_inc),  adap->bar2 + udb + 8);
+		ret = t4_bar2_sge_qregs(adap, qid, T4_BAR2_QTYPE_EGRESS,
+					&bar2_qoffset, &bar2_qid);
+		if (ret)
+			dev_err(adap->pdev_dev, "doorbell drop recovery: "
+				"qid=%d, pidx_inc=%d\n", qid, pidx_inc);
+		else
+			writel(PIDX_T5(pidx_inc) | QID(bar2_qid),
+			       adap->bar2 + bar2_qoffset + SGE_UDB_KDOORBELL);
 
 		/* Re-enable BAR2 WC */
 		t4_set_reg_field(adap, 0x10b0, 1<<15, 1<<15);
@@ -4069,12 +4072,8 @@ static void uld_attach(struct adapter *adap, unsigned int uld)
 	lli.adapter_type = adap->params.chip;
 	lli.iscsi_iolen = MAXRXDATA_GET(t4_read_reg(adap, TP_PARA_REG2));
 	lli.cclk_ps = 1000000000 / adap->params.vpd.cclk;
-	lli.udb_density = 1 << QUEUESPERPAGEPF0_GET(
-			t4_read_reg(adap, SGE_EGRESS_QUEUES_PER_PAGE_PF) >>
-			(adap->fn * 4));
-	lli.ucq_density = 1 << QUEUESPERPAGEPF0_GET(
-			t4_read_reg(adap, SGE_INGRESS_QUEUES_PER_PAGE_PF) >>
-			(adap->fn * 4));
+	lli.udb_density = 1 << adap->params.sge.eq_qpp;
+	lli.ucq_density = 1 << adap->params.sge.iq_qpp;
 	lli.filt_mode = adap->params.tp.vlan_pri_map;
 	/* MODQ_REQ_MAP sets queues 0-3 to chan 0-3 */
 	for (i = 0; i < NCHAN; i++)
@@ -5926,6 +5925,7 @@ static int adap_init0(struct adapter *adap)
 		t4_load_mtus(adap, adap->params.mtus, adap->params.a_wnd,
 			     adap->params.b_wnd);
 	}
+	t4_init_sge_params(adap);
 	t4_init_tp_params(adap);
 	adap->flags |= FW_OK;
 	return 0;

drivers/net/ethernet/chelsio/cxgb4/cxgb4_uld.h

@@ -305,4 +305,11 @@ void cxgb4_enable_db_coalescing(struct net_device *dev);
 int cxgb4_read_tpte(struct net_device *dev, u32 stag, __be32 *tpte);
 u64 cxgb4_read_sge_timestamp(struct net_device *dev);
 
+enum cxgb4_bar2_qtype { CXGB4_BAR2_QTYPE_EGRESS, CXGB4_BAR2_QTYPE_INGRESS };
+int cxgb4_bar2_sge_qregs(struct net_device *dev,
+			 unsigned int qid,
+			 enum cxgb4_bar2_qtype qtype,
+			 u64 *pbar2_qoffset,
+			 unsigned int *pbar2_qid);
+
 #endif  /* !__CXGB4_OFLD_H */

drivers/net/ethernet/chelsio/cxgb4/sge.c

@@ -527,14 +527,16 @@ static inline void ring_fl_db(struct adapter *adap, struct sge_fl *q)
 		val |= DBPRIO(1);
 		wmb();
 
-		/* If we're on T4, use the old doorbell mechanism; otherwise
-		 * use the new BAR2 mechanism.
+		/* If we don't have access to the new User Doorbell (T5+), use
+		 * the old doorbell mechanism; otherwise use the new BAR2
+		 * mechanism.
 		 */
-		if (is_t4(adap->params.chip)) {
+		if (unlikely(q->bar2_addr == NULL)) {
 			t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL),
 				     val | QID(q->cntxt_id));
 		} else {
-			writel(val,  adap->bar2 + q->udb + SGE_UDB_KDOORBELL);
+			writel(val | QID(q->bar2_qid),
+			       q->bar2_addr + SGE_UDB_KDOORBELL);
 
 			/* This Write memory Barrier will force the write to
 			 * the User Doorbell area to be flushed.
@@ -850,14 +852,13 @@ static void write_sgl(const struct sk_buff *skb, struct sge_txq *q,
 		*end = 0;
 }
 
-/* This function copies a tx_desc struct to memory mapped BAR2 space(user space
- * writes). For coalesced WR SGE, fetches data from the FIFO instead of from
- * Host.
+/* This function copies 64 byte coalesced work request to
+ * memory mapped BAR2 space. For coalesced WR SGE fetches
+ * data from the FIFO instead of from Host.
  */
-static void cxgb_pio_copy(u64 __iomem *dst, struct tx_desc *desc)
+static void cxgb_pio_copy(u64 __iomem *dst, u64 *src)
 {
-	int count = sizeof(*desc) / sizeof(u64);
-	u64 *src = (u64 *)desc;
+	int count = 8;
 
 	while (count) {
 		writeq(*src, dst);
@@ -879,7 +880,10 @@ static inline void ring_tx_db(struct adapter *adap, struct sge_txq *q, int n)
 {
 	wmb();            /* write descriptors before telling HW */
 
-	if (is_t4(adap->params.chip)) {
+	/* If we don't have access to the new User Doorbell (T5+), use the old
+	 * doorbell mechanism; otherwise use the new BAR2 mechanism.
+	 */
+	if (unlikely(q->bar2_addr == NULL)) {
 		u32 val = PIDX(n);
 		unsigned long flags;
 
@@ -905,21 +909,22 @@ static inline void ring_tx_db(struct adapter *adap, struct sge_txq *q, int n)
 		 */
 		WARN_ON(val & DBPRIO(1));
 
-		/* For T5 and later we use the Write-Combine mapped BAR2 User
-		 * Doorbell mechanism.  If we're only writing a single TX
-		 * Descriptor and TX Write Combining hasn't been disabled, we
-		 * can use the Write Combining Gather Buffer; otherwise we use
-		 * the simple doorbell.
+		/* If we're only writing a single TX Descriptor and we can use
+		 * Inferred QID registers, we can use the Write Combining
+		 * Gather Buffer; otherwise we use the simple doorbell.
 		 */
-		if (n == 1) {
+		if (n == 1 && q->bar2_qid == 0) {
 			int index = (q->pidx
 				     ? (q->pidx - 1)
 				     : (q->size - 1));
+			u64 *wr = (u64 *)&q->desc[index];
 
-			cxgb_pio_copy(adap->bar2 + q->udb + SGE_UDB_WCDOORBELL,
-				      q->desc + index);
+			cxgb_pio_copy((u64 __iomem *)
+				      (q->bar2_addr + SGE_UDB_WCDOORBELL),
+				      wr);
 		} else {
-			writel(val,  adap->bar2 + q->udb + SGE_UDB_KDOORBELL);
+			writel(val | QID(q->bar2_qid),
+			       q->bar2_addr + SGE_UDB_KDOORBELL);
 		}
 
 		/* This Write Memory Barrier will force the write to the User
@@ -1997,11 +2002,16 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 		params = QINTR_TIMER_IDX(7);
 
 	val = CIDXINC(work_done) | SEINTARM(params);
-	if (is_t4(q->adap->params.chip)) {
+
+	/* If we don't have access to the new User GTS (T5+), use the old
+	 * doorbell mechanism; otherwise use the new BAR2 mechanism.
+	 */
+	if (unlikely(q->bar2_addr == NULL)) {
 		t4_write_reg(q->adap, MYPF_REG(SGE_PF_GTS),
 			     val | INGRESSQID((u32)q->cntxt_id));
 	} else {
-		writel(val, q->adap->bar2 + q->udb + SGE_UDB_GTS);
+		writel(val | INGRESSQID(q->bar2_qid),
+		       q->bar2_addr + SGE_UDB_GTS);
 		wmb();
 	}
 	return work_done;
@@ -2047,11 +2057,16 @@ static unsigned int process_intrq(struct adapter *adap)
 	}
 
 	val =  CIDXINC(credits) | SEINTARM(q->intr_params);
-	if (is_t4(adap->params.chip)) {
+
+	/* If we don't have access to the new User GTS (T5+), use the old
+	 * doorbell mechanism; otherwise use the new BAR2 mechanism.
+	 */
+	if (unlikely(q->bar2_addr == NULL)) {
 		t4_write_reg(adap, MYPF_REG(SGE_PF_GTS),
 			     val | INGRESSQID(q->cntxt_id));
 	} else {
-		writel(val, adap->bar2 + q->udb + SGE_UDB_GTS);
+		writel(val | INGRESSQID(q->bar2_qid),
+		       q->bar2_addr + SGE_UDB_GTS);
 		wmb();
 	}
 	spin_unlock(&adap->sge.intrq_lock);
@@ -2235,48 +2250,32 @@ static void sge_tx_timer_cb(unsigned long data)
 }
 
 /**
- *      udb_address - return the BAR2 User Doorbell address for a Queue
- *      @adap: the adapter
- *      @cntxt_id: the Queue Context ID
- *      @qpp: Queues Per Page (for all PFs)
+ *	bar2_address - return the BAR2 address for an SGE Queue's Registers
+ *	@adapter: the adapter
+ *	@qid: the SGE Queue ID
+ *	@qtype: the SGE Queue Type (Egress or Ingress)
+ *	@pbar2_qid: BAR2 Queue ID or 0 for Queue ID inferred SGE Queues
  *
- *      Returns the BAR2 address of the user Doorbell associated with the
- *      indicated Queue Context ID.  Note that this is only applicable
- *      for T5 and later.
- */
-static u64 udb_address(struct adapter *adap, unsigned int cntxt_id,
-		       unsigned int qpp)
-{
-	u64 udb;
-	unsigned int s_qpp;
-	unsigned short udb_density;
-	unsigned long qpshift;
-	int page;
-
-	BUG_ON(is_t4(adap->params.chip));
-
-	s_qpp = (QUEUESPERPAGEPF0 +
-		(QUEUESPERPAGEPF1 - QUEUESPERPAGEPF0) * adap->fn);
-	udb_density = 1 << ((qpp >> s_qpp) & QUEUESPERPAGEPF0_MASK);
-	qpshift = PAGE_SHIFT - ilog2(udb_density);
-	udb = (u64)cntxt_id << qpshift;
-	udb &= PAGE_MASK;
-	page = udb / PAGE_SIZE;
-	udb += (cntxt_id - (page * udb_density)) * SGE_UDB_SIZE;
-
-	return udb;
-}
+ *	Returns the BAR2 address for the SGE Queue Registers associated with
+ *	@qid.  If BAR2 SGE Registers aren't available, returns NULL.  Also
+ *	returns the BAR2 Queue ID to be used with writes to the BAR2 SGE
+ *	Queue Registers.  If the BAR2 Queue ID is 0, then "Inferred Queue ID"
+ *	Registers are supported (e.g. the Write Combining Doorbell Buffer).
+ */
+static void __iomem *bar2_address(struct adapter *adapter,
+				  unsigned int qid,
+				  enum t4_bar2_qtype qtype,
+				  unsigned int *pbar2_qid)
+{
+	u64 bar2_qoffset;
+	int ret;
 
-static u64 udb_address_eq(struct adapter *adap, unsigned int cntxt_id)
-{
-	return udb_address(adap, cntxt_id,
-			   t4_read_reg(adap, SGE_EGRESS_QUEUES_PER_PAGE_PF));
-}
+	ret = t4_bar2_sge_qregs(adapter, qid, qtype,
+				&bar2_qoffset, pbar2_qid);
+	if (ret)
+		return NULL;
 
-static u64 udb_address_iq(struct adapter *adap, unsigned int cntxt_id)
-{
-	return udb_address(adap, cntxt_id,
-			   t4_read_reg(adap, SGE_INGRESS_QUEUES_PER_PAGE_PF));
+	return adapter->bar2 + bar2_qoffset;
 }
 
 int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
@@ -2344,8 +2343,10 @@ int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
 	iq->next_intr_params = iq->intr_params;
 	iq->cntxt_id = ntohs(c.iqid);
 	iq->abs_id = ntohs(c.physiqid);
-	if (!is_t4(adap->params.chip))
-		iq->udb = udb_address_iq(adap, iq->cntxt_id);
+	iq->bar2_addr = bar2_address(adap,
+				     iq->cntxt_id,
+				     T4_BAR2_QTYPE_INGRESS,
+				     &iq->bar2_qid);
 	iq->size--;                           /* subtract status entry */
 	iq->netdev = dev;
 	iq->handler = hnd;
@@ -2362,11 +2363,13 @@ int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
 		fl->alloc_failed = fl->large_alloc_failed = fl->starving = 0;
 		adap->sge.egr_map[fl->cntxt_id - adap->sge.egr_start] = fl;
 
-		/* Note, we must initialize the Free List User Doorbell
-		 * address before refilling the Free List!
+		/* Note, we must initialize the BAR2 Free List User Doorbell
+		 * information before refilling the Free List!
 		 */
-		if (!is_t4(adap->params.chip))
-			fl->udb = udb_address_eq(adap, fl->cntxt_id);
+		fl->bar2_addr = bar2_address(adap,
+					     fl->cntxt_id,
+					     T4_BAR2_QTYPE_EGRESS,
+					     &fl->bar2_qid);
 		refill_fl(adap, fl, fl_cap(fl), GFP_KERNEL);
 	}
 	return 0;
@@ -2392,9 +2395,10 @@ int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
 static void init_txq(struct adapter *adap, struct sge_txq *q, unsigned int id)
 {
 	q->cntxt_id = id;
-	if (!is_t4(adap->params.chip))
-		q->udb = udb_address_eq(adap, q->cntxt_id);
-
+	q->bar2_addr = bar2_address(adap,
+				    q->cntxt_id,
+				    T4_BAR2_QTYPE_EGRESS,
+				    &q->bar2_qid);
 	q->in_use = 0;
 	q->cidx = q->pidx = 0;
 	q->stops = q->restarts = 0;

drivers/net/ethernet/chelsio/cxgb4vf/adapter.h

@@ -138,6 +138,8 @@ struct sge_fl {
 	struct rx_sw_desc *sdesc;	/* address of SW RX descriptor ring */
 	__be64 *desc;			/* address of HW RX descriptor ring */
 	dma_addr_t addr;		/* PCI bus address of hardware ring */
+	void __iomem *bar2_addr;	/* address of BAR2 Queue registers */
+	unsigned int bar2_qid;		/* Queue ID for BAR2 Queue registers */
 };
 
 /*
@@ -178,6 +180,8 @@ struct sge_rspq {
 	u16 abs_id;			/* SGE abs QID for the response Q */
 	__be64 *desc;			/* address of hardware response ring */
 	dma_addr_t phys_addr;		/* PCI bus address of ring */
+	void __iomem *bar2_addr;	/* address of BAR2 Queue registers */
+	unsigned int bar2_qid;		/* Queue ID for BAR2 Queue registers */
 	unsigned int iqe_len;		/* entry size */
 	unsigned int size;		/* capcity of response Q */
 	struct adapter *adapter;	/* our adapter */
@@ -240,6 +244,8 @@ struct sge_txq {
 	struct tx_sw_desc *sdesc;	/* address of SW TX descriptor ring */
 	struct sge_qstat *stat;		/* queue status entry */
 	dma_addr_t phys_addr;		/* PCI bus address of hardware ring */
+	void __iomem *bar2_addr;	/* address of BAR2 Queue registers */
+	unsigned int bar2_qid;		/* Queue ID for BAR2 Queue registers */
 };
 
 /*
@@ -345,6 +351,7 @@ struct sge {
 struct adapter {
 	/* PCI resources */
 	void __iomem *regs;
+	void __iomem *bar2;
 	struct pci_dev *pdev;
 	struct device *pdev_dev;
 

drivers/net/ethernet/chelsio/cxgb4vf/cxgb4vf_main.c

@@ -2095,7 +2095,6 @@ static int adap_init0(struct adapter *adapter)
 	unsigned int ethqsets;
 	int err;
 	u32 param, val = 0;
-	unsigned int chipid;
 
 	/*
 	 * Wait for the device to become ready before proceeding ...
@@ -2123,17 +2122,6 @@ static int adap_init0(struct adapter *adapter)
 		return err;
 	}
 
-	adapter->params.chip = 0;
-	switch (adapter->pdev->device >> 12) {
-	case CHELSIO_T4:
-		adapter->params.chip = CHELSIO_CHIP_CODE(CHELSIO_T4, 0);
-		break;
-	case CHELSIO_T5:
-		chipid = G_REV(t4_read_reg(adapter, A_PL_VF_REV));
-		adapter->params.chip |= CHELSIO_CHIP_CODE(CHELSIO_T5, chipid);
-		break;
-	}
-
 	/*
 	 * Grab basic operational parameters.  These will predominantly have
 	 * been set up by the Physical Function Driver or will be hard coded

drivers/net/ethernet/chelsio/cxgb4vf/sge.c

@@ -525,19 +525,40 @@ static inline void ring_fl_db(struct adapter *adapter, struct sge_fl *fl)
 {
 	u32 val;
 
-	/*
-	 * The SGE keeps track of its Producer and Consumer Indices in terms
+	/* The SGE keeps track of its Producer and Consumer Indices in terms
 	 * of Egress Queue Units so we can only tell it about integral numbers
 	 * of multiples of Free List Entries per Egress Queue Units ...
 	 */
 	if (fl->pend_cred >= FL_PER_EQ_UNIT) {
-		val = PIDX(fl->pend_cred / FL_PER_EQ_UNIT);
-		if (!is_t4(adapter->params.chip))
-			val |= DBTYPE(1);
+		if (is_t4(adapter->params.chip))
+			val = PIDX(fl->pend_cred / FL_PER_EQ_UNIT);
+		else
+			val = PIDX_T5(fl->pend_cred / FL_PER_EQ_UNIT) |
+			      DBTYPE(1);
+		val |= DBPRIO(1);
+
+		/* Make sure all memory writes to the Free List queue are
+		 * committed before we tell the hardware about them.
+		 */
 		wmb();
-		t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
-			     DBPRIO(1) |
-			     QID(fl->cntxt_id) | val);
+
+		/* If we don't have access to the new User Doorbell (T5+), use
+		 * the old doorbell mechanism; otherwise use the new BAR2
+		 * mechanism.
+		 */
+		if (unlikely(fl->bar2_addr == NULL)) {
+			t4_write_reg(adapter,
+				     T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
+				     QID(fl->cntxt_id) | val);
+		} else {
+			writel(val | QID(fl->bar2_qid),
+			       fl->bar2_addr + SGE_UDB_KDOORBELL);
+
+			/* This Write memory Barrier will force the write to
+			 * the User Doorbell area to be flushed.
+			 */
+			wmb();
+		}
 		fl->pend_cred %= FL_PER_EQ_UNIT;
 	}
 }
@@ -949,14 +970,74 @@ static void write_sgl(const struct sk_buff *skb, struct sge_txq *tq,
 static inline void ring_tx_db(struct adapter *adapter, struct sge_txq *tq,
 			      int n)
 {
-	/*
-	 * Warn if we write doorbells with the wrong priority and write
-	 * descriptors before telling HW.
+	/* Make sure that all writes to the TX Descriptors are committed
+	 * before we tell the hardware about them.
 	 */
-	WARN_ON((QID(tq->cntxt_id) | PIDX(n)) & DBPRIO(1));
 	wmb();
-	t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
-		     QID(tq->cntxt_id) | PIDX(n));
+
+	/* If we don't have access to the new User Doorbell (T5+), use the old
+	 * doorbell mechanism; otherwise use the new BAR2 mechanism.
+	 */
+	if (unlikely(tq->bar2_addr == NULL)) {
+		u32 val = PIDX(n);
+
+		t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
+			     QID(tq->cntxt_id) | val);
+	} else {
+		u32 val = PIDX_T5(n);
+
+		/* T4 and later chips share the same PIDX field offset within
+		 * the doorbell, but T5 and later shrank the field in order to
+		 * gain a bit for Doorbell Priority.  The field was absurdly
+		 * large in the first place (14 bits) so we just use the T5
+		 * and later limits and warn if a Queue ID is too large.
+		 */
+		WARN_ON(val & DBPRIO(1));
+
+		/* If we're only writing a single Egress Unit and the BAR2
+		 * Queue ID is 0, we can use the Write Combining Doorbell
+		 * Gather Buffer; otherwise we use the simple doorbell.
+		 */
+		if (n == 1 && tq->bar2_qid == 0) {
+			unsigned int index = (tq->pidx
+					      ? (tq->pidx - 1)
+					      : (tq->size - 1));
+			__be64 *src = (__be64 *)&tq->desc[index];
+			__be64 __iomem *dst = (__be64 *)(tq->bar2_addr +
+							 SGE_UDB_WCDOORBELL);
+			unsigned int count = EQ_UNIT / sizeof(__be64);
+
+			/* Copy the TX Descriptor in a tight loop in order to
+			 * try to get it to the adapter in a single Write
+			 * Combined transfer on the PCI-E Bus.  If the Write
+			 * Combine fails (say because of an interrupt, etc.)
+			 * the hardware will simply take the last write as a
+			 * simple doorbell write with a PIDX Increment of 1
+			 * and will fetch the TX Descriptor from memory via
+			 * DMA.
+			 */
+			while (count) {
+				writeq(*src, dst);
+				src++;
+				dst++;
+				count--;
+			}
+		} else
+			writel(val | QID(tq->bar2_qid),
+			       tq->bar2_addr + SGE_UDB_KDOORBELL);
+
+		/* This Write Memory Barrier will force the write to the User
+		 * Doorbell area to be flushed.  This is needed to prevent
+		 * writes on different CPUs for the same queue from hitting
+		 * the adapter out of order.  This is required when some Work
+		 * Requests take the Write Combine Gather Buffer path (user
+		 * doorbell area offset [SGE_UDB_WCDOORBELL..+63]) and some
+		 * take the traditional path where we simply increment the
+		 * PIDX (User Doorbell area SGE_UDB_KDOORBELL) and have the
+		 * hardware DMA read the actual Work Request.
+		 */
+		wmb();
+	}
 }
 
 /**
@@ -1782,6 +1863,7 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	unsigned int intr_params;
 	struct sge_rspq *rspq = container_of(napi, struct sge_rspq, napi);
 	int work_done = process_responses(rspq, budget);
+	u32 val;
 
 	if (likely(work_done < budget)) {
 		napi_complete(napi);
@@ -1793,11 +1875,16 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	if (unlikely(work_done == 0))
 		rspq->unhandled_irqs++;
 
-	t4_write_reg(rspq->adapter,
-		     T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
-		     CIDXINC(work_done) |
-		     INGRESSQID((u32)rspq->cntxt_id) |
-		     SEINTARM(intr_params));
+	val = CIDXINC(work_done) | SEINTARM(intr_params);
+	if (is_t4(rspq->adapter->params.chip)) {
+		t4_write_reg(rspq->adapter,
+			     T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
+			     val | INGRESSQID((u32)rspq->cntxt_id));
+	} else {
+		writel(val | INGRESSQID(rspq->bar2_qid),
+		       rspq->bar2_addr + SGE_UDB_GTS);
+		wmb();
+	}
 	return work_done;
 }
 
@@ -1822,6 +1909,7 @@ static unsigned int process_intrq(struct adapter *adapter)
 	struct sge *s = &adapter->sge;
 	struct sge_rspq *intrq = &s->intrq;
 	unsigned int work_done;
+	u32 val;
 
 	spin_lock(&adapter->sge.intrq_lock);
 	for (work_done = 0; ; work_done++) {
@@ -1887,10 +1975,15 @@ static unsigned int process_intrq(struct adapter *adapter)
 		rspq_next(intrq);
 	}
 
-	t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
-		     CIDXINC(work_done) |
-		     INGRESSQID(intrq->cntxt_id) |
-		     SEINTARM(intrq->intr_params));
+	val = CIDXINC(work_done) | SEINTARM(intrq->intr_params);
+	if (is_t4(adapter->params.chip))
+		t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
+			     val | INGRESSQID(intrq->cntxt_id));
+	else {
+		writel(val | INGRESSQID(intrq->bar2_qid),
+		       intrq->bar2_addr + SGE_UDB_GTS);
+		wmb();
+	}
 
 	spin_unlock(&adapter->sge.intrq_lock);
 
@@ -2035,6 +2128,35 @@ static void sge_tx_timer_cb(unsigned long data)
 	mod_timer(&s->tx_timer, jiffies + (budget ? TX_QCHECK_PERIOD : 2));
 }
 
+/**
+ *	bar2_address - return the BAR2 address for an SGE Queue's Registers
+ *	@adapter: the adapter
+ *	@qid: the SGE Queue ID
+ *	@qtype: the SGE Queue Type (Egress or Ingress)
+ *	@pbar2_qid: BAR2 Queue ID or 0 for Queue ID inferred SGE Queues
+ *
+ *	Returns the BAR2 address for the SGE Queue Registers associated with
+ *	@qid.  If BAR2 SGE Registers aren't available, returns NULL.  Also
+ *	returns the BAR2 Queue ID to be used with writes to the BAR2 SGE
+ *	Queue Registers.  If the BAR2 Queue ID is 0, then "Inferred Queue ID"
+ *	Registers are supported (e.g. the Write Combining Doorbell Buffer).
+ */
+static void __iomem *bar2_address(struct adapter *adapter,
+				  unsigned int qid,
+				  enum t4_bar2_qtype qtype,
+				  unsigned int *pbar2_qid)
+{
+	u64 bar2_qoffset;
+	int ret;
+
+	ret = t4_bar2_sge_qregs(adapter, qid, qtype,
+				&bar2_qoffset, pbar2_qid);
+	if (ret)
+		return NULL;
+
+	return adapter->bar2 + bar2_qoffset;
+}
+
 /**
  *	t4vf_sge_alloc_rxq - allocate an SGE RX Queue
  *	@adapter: the adapter
@@ -2166,6 +2288,10 @@ int t4vf_sge_alloc_rxq(struct adapter *adapter, struct sge_rspq *rspq,
 	rspq->gen = 1;
 	rspq->next_intr_params = rspq->intr_params;
 	rspq->cntxt_id = be16_to_cpu(rpl.iqid);
+	rspq->bar2_addr = bar2_address(adapter,
+				       rspq->cntxt_id,
+				       T4_BAR2_QTYPE_INGRESS,
+				       &rspq->bar2_qid);
 	rspq->abs_id = be16_to_cpu(rpl.physiqid);
 	rspq->size--;			/* subtract status entry */
 	rspq->adapter = adapter;
@@ -2184,6 +2310,15 @@ int t4vf_sge_alloc_rxq(struct adapter *adapter, struct sge_rspq *rspq,
 		fl->alloc_failed = 0;
 		fl->large_alloc_failed = 0;
 		fl->starving = 0;
+
+		/* Note, we must initialize the BAR2 Free List User Doorbell
+		 * information before refilling the Free List!
+		 */
+		fl->bar2_addr = bar2_address(adapter,
+					     fl->cntxt_id,
+					     T4_BAR2_QTYPE_EGRESS,
+					     &fl->bar2_qid);
+
 		refill_fl(adapter, fl, fl_cap(fl), GFP_KERNEL);
 	}
 
@@ -2296,6 +2431,10 @@ int t4vf_sge_alloc_eth_txq(struct adapter *adapter, struct sge_eth_txq *txq,
 	txq->q.pidx = 0;
 	txq->q.stat = (void *)&txq->q.desc[txq->q.size];
 	txq->q.cntxt_id = FW_EQ_ETH_CMD_EQID_G(be32_to_cpu(rpl.eqid_pkd));
+	txq->q.bar2_addr = bar2_address(adapter,
+					txq->q.cntxt_id,
+					T4_BAR2_QTYPE_EGRESS,
+					&txq->q.bar2_qid);
 	txq->q.abs_id =
 		FW_EQ_ETH_CMD_PHYSEQID_G(be32_to_cpu(rpl.physeqid_pkd));
 	txq->txq = devq;