cxgb4: Use BAR2 Going To Sleep (GTS) for T5 and later.

Use BAR2 GTS for T5. If we are on T4 use the old doorbell mechanism;
otherwise ue the new BAR2 mechanism. Use BAR2 doorbells for refilling FL's.

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

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

@@ -431,6 +431,7 @@ 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 */
 };
 
 /* A packet gather list */
@@ -459,6 +460,7 @@ 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 */
 	unsigned int iqe_len;       /* entry size */
 	unsigned int size;          /* capacity of response queue */
 	struct adapter *adap;
@@ -516,7 +518,7 @@ struct sge_txq {
 	int db_disabled;
 	unsigned short db_pidx;
 	unsigned short db_pidx_inc;
-	u64 udb;
+	u64 udb;                    /* BAR2 offset of User Doorbell area */
 };
 
 struct sge_eth_txq {                /* state for an SGE Ethernet Tx queue */

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

@@ -521,9 +521,23 @@ static inline void ring_fl_db(struct adapter *adap, struct sge_fl *q)
 		val = PIDX(q->pend_cred / 8);
 		if (!is_t4(adap->params.chip))
 			val |= DBTYPE(1);
+		val |= DBPRIO(1);
 		wmb();
-		t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL), DBPRIO(1) |
-			     QID(q->cntxt_id) | val);
+
+		/* If we're on T4, use the old doorbell mechanism; otherwise
+		 * use the new BAR2 mechanism.
+		 */
+		if (is_t4(adap->params.chip)) {
+			t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL),
+				     val | QID(q->cntxt_id));
+		} else {
+			writel(val,  adap->bar2 + q->udb + SGE_UDB_KDOORBELL);
+
+			/* This Write memory Barrier will force the write to
+			 * the User Doorbell area to be flushed.
+			 */
+			wmb();
+		}
 		q->pend_cred &= 7;
 	}
 }
@@ -859,30 +873,66 @@ static void cxgb_pio_copy(u64 __iomem *dst, u64 *src)
  */
 static inline void ring_tx_db(struct adapter *adap, struct sge_txq *q, int n)
 {
-	unsigned int *wr, index;
+	wmb();            /* write descriptors before telling HW */
+
+	if (is_t4(adap->params.chip)) {
+		u32 val = PIDX(n);
 		unsigned long flags;
 
-	wmb();            /* write descriptors before telling HW */
+		/* For T4 we need to participate in the Doorbell Recovery
+		 * mechanism.
+		 */
 		spin_lock_irqsave(&q->db_lock, flags);
-	if (!q->db_disabled) {
-		if (is_t4(adap->params.chip)) {
+		if (!q->db_disabled)
 			t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL),
-				     QID(q->cntxt_id) | PIDX(n));
+				     QID(q->cntxt_id) | val);
+		else
+			q->db_pidx_inc += n;
+		q->db_pidx = q->pidx;
+		spin_unlock_irqrestore(&q->db_lock, flags);
 	} 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));
+
+		/* 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 (n == 1) {
-				index = q->pidx ? (q->pidx - 1) : (q->size - 1);
-				wr = (unsigned int *)&q->desc[index];
+			int index = (q->pidx
+				     ? (q->pidx - 1)
+				     : (q->size - 1));
+			unsigned int *wr = (unsigned int *)&q->desc[index];
+
 			cxgb_pio_copy((u64 __iomem *)
-					      (adap->bar2 + q->udb + 64),
+				      (adap->bar2 + q->udb +
+				       SGE_UDB_WCDOORBELL),
 				      (u64 *)wr);
-			} else
-				writel(n,  adap->bar2 + q->udb + 8);
+		} else {
+			writel(val,  adap->bar2 + q->udb + 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();
 	}
-	} else
-		q->db_pidx_inc += n;
-	q->db_pidx = q->pidx;
-	spin_unlock_irqrestore(&q->db_lock, flags);
 }
 
 /**
@@ -1916,6 +1966,7 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	unsigned int params;
 	struct sge_rspq *q = container_of(napi, struct sge_rspq, napi);
 	int work_done = process_responses(q, budget);
+	u32 val;
 
 	if (likely(work_done < budget)) {
 		napi_complete(napi);
@@ -1924,8 +1975,14 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	} else
 		params = QINTR_TIMER_IDX(7);
 
-	t4_write_reg(q->adap, MYPF_REG(SGE_PF_GTS), CIDXINC(work_done) |
-		     INGRESSQID((u32)q->cntxt_id) | SEINTARM(params));
+	val = CIDXINC(work_done) | SEINTARM(params);
+	if (is_t4(q->adap->params.chip)) {
+		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);
+		wmb();
+	}
 	return work_done;
 }
 
@@ -1949,6 +2006,7 @@ static unsigned int process_intrq(struct adapter *adap)
 	unsigned int credits;
 	const struct rsp_ctrl *rc;
 	struct sge_rspq *q = &adap->sge.intrq;
+	u32 val;
 
 	spin_lock(&adap->sge.intrq_lock);
 	for (credits = 0; ; credits++) {
@@ -1967,8 +2025,14 @@ static unsigned int process_intrq(struct adapter *adap)
 		rspq_next(q);
 	}
 
-	t4_write_reg(adap, MYPF_REG(SGE_PF_GTS), CIDXINC(credits) |
-		     INGRESSQID(q->cntxt_id) | SEINTARM(q->intr_params));
+	val =  CIDXINC(credits) | SEINTARM(q->intr_params);
+	if (is_t4(adap->params.chip)) {
+		t4_write_reg(adap, MYPF_REG(SGE_PF_GTS),
+			     val | INGRESSQID(q->cntxt_id));
+	} else {
+		writel(val, adap->bar2 + q->udb + SGE_UDB_GTS);
+		wmb();
+	}
 	spin_unlock(&adap->sge.intrq_lock);
 	return credits;
 }
@@ -2149,6 +2213,51 @@ static void sge_tx_timer_cb(unsigned long data)
 	mod_timer(&s->tx_timer, jiffies + (budget ? TX_QCHECK_PERIOD : 2));
 }
 
+/**
+ *      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)
+ *
+ *      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 = cntxt_id << qpshift;
+	udb &= PAGE_MASK;
+	page = udb / PAGE_SIZE;
+	udb += (cntxt_id - (page * udb_density)) * SGE_UDB_SIZE;
+
+	return udb;
+}
+
+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));
+}
+
+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));
+}
+
 int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
 		     struct net_device *dev, int intr_idx,
 		     struct sge_fl *fl, rspq_handler_t hnd)
@@ -2214,6 +2323,8 @@ 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->size--;                           /* subtract status entry */
 	iq->netdev = dev;
 	iq->handler = hnd;
@@ -2229,6 +2340,12 @@ int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
 		fl->pidx = fl->cidx = 0;
 		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!
+		 */
+		if (!is_t4(adap->params.chip))
+			fl->udb = udb_address_eq(adap, fl->cntxt_id);
 		refill_fl(adap, fl, fl_cap(fl), GFP_KERNEL);
 	}
 	return 0;
@@ -2254,21 +2371,8 @@ 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)) {
-		unsigned int s_qpp;
-		unsigned short udb_density;
-		unsigned long qpshift;
-		int page;
-
-		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);
-		q->udb = q->cntxt_id << qpshift;
-		q->udb &= PAGE_MASK;
-		page = q->udb / PAGE_SIZE;
-		q->udb += (q->cntxt_id - (page * udb_density)) * 128;
-	}
+	if (!is_t4(adap->params.chip))
+		q->udb = udb_address_eq(adap, q->cntxt_id);
 
 	q->in_use = 0;
 	q->cidx = q->pidx = 0;

drivers/net/ethernet/chelsio/cxgb4/t4_regs.h

@@ -157,8 +157,27 @@
 #define  QUEUESPERPAGEPF0_MASK   0x0000000fU
 #define  QUEUESPERPAGEPF0_GET(x) ((x) & QUEUESPERPAGEPF0_MASK)
 
+#define QUEUESPERPAGEPF0    0
 #define QUEUESPERPAGEPF1    4
 
+/* T5 and later support a new BAR2-based doorbell mechanism for Egress Queues.
+ * The User Doorbells are each 128 bytes in length with a Simple Doorbell at
+ * offsets 8x and a Write Combining single 64-byte Egress Queue Unit
+ * (X_IDXSIZE_UNIT) Gather Buffer interface at offset 64.  For Ingress Queues,
+ * we have a Going To Sleep register at offsets 8x+4.
+ *
+ * As noted above, we have many instances of the Simple Doorbell and Going To
+ * Sleep registers at offsets 8x and 8x+4, respectively.  We want to use a
+ * non-64-byte aligned offset for the Simple Doorbell in order to attempt to
+ * avoid buffering of the writes to the Simple Doorbell and we want to use a
+ * non-contiguous offset for the Going To Sleep writes in order to avoid
+ * possible combining between them.
+ */
+#define SGE_UDB_SIZE            128
+#define SGE_UDB_KDOORBELL       8
+#define SGE_UDB_GTS             20
+#define SGE_UDB_WCDOORBELL      64
+
 #define SGE_INT_CAUSE1 0x1024
 #define SGE_INT_CAUSE2 0x1030
 #define SGE_INT_CAUSE3 0x103c