RDMA/cxgb4: Force T5 connections to use TAHOE congestion control

This is required to work around a T5 HW issue.
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/cxgb4/cm.c

@@ -587,6 +587,10 @@ static int send_connect(struct c4iw_ep *ep)
 		opt2 |= SACK_EN(1);
 	if (wscale && enable_tcp_window_scaling)
 		opt2 |= WND_SCALE_EN(1);
+	if (is_t5(ep->com.dev->rdev.lldi.adapter_type)) {
+		opt2 |= T5_OPT_2_VALID;
+		opt2 |= V_CONG_CNTRL(CONG_ALG_TAHOE);
+	}
 	t4_set_arp_err_handler(skb, NULL, act_open_req_arp_failure);
 
 	if (is_t4(ep->com.dev->rdev.lldi.adapter_type)) {
@@ -2018,6 +2022,10 @@ static void accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
 		if (tcph->ece && tcph->cwr)
 			opt2 |= CCTRL_ECN(1);
 	}
+	if (is_t5(ep->com.dev->rdev.lldi.adapter_type)) {
+		opt2 |= T5_OPT_2_VALID;
+		opt2 |= V_CONG_CNTRL(CONG_ALG_TAHOE);
+	}
 
 	rpl = cplhdr(skb);
 	INIT_TP_WR(rpl, ep->hwtid);

drivers/infiniband/hw/cxgb4/t4fw_ri_api.h

@@ -836,4 +836,18 @@ struct ulptx_idata {
 #define V_RX_DACK_CHANGE(x) ((x) << S_RX_DACK_CHANGE)
 #define F_RX_DACK_CHANGE    V_RX_DACK_CHANGE(1U)
 
+enum {                     /* TCP congestion control algorithms */
+	CONG_ALG_RENO,
+	CONG_ALG_TAHOE,
+	CONG_ALG_NEWRENO,
+	CONG_ALG_HIGHSPEED
+};
+
+#define S_CONG_CNTRL    14
+#define M_CONG_CNTRL    0x3
+#define V_CONG_CNTRL(x) ((x) << S_CONG_CNTRL)
+#define G_CONG_CNTRL(x) (((x) >> S_CONG_CNTRL) & M_CONG_CNTRL)
+
+#define T5_OPT_2_VALID       (1 << 31)
+
 #endif /* _T4FW_RI_API_H_ */