UBUNTU: SAUCE: bnxt_en_bpo: Fix TX timeout during netpoll

BugLink: http://bugs.launchpad.net/bugs/1814095

The current netpoll implementation in the bnxt_en driver
 has problems that may miss TX completion events.  bnxt_poll_work() in effect
 is only handling at most 1 TX packet before exiting.  In addition, there may
 be in flight TX completions that ->poll() may miss even after we fix
 bnxt_poll_work() to handle all visible TX completions. netpoll may not call
 ->poll() again and HW may not generate IRQ because the driver does not ARM
 the IRQ when the budget (0 for netpoll) is reached.

We fix it by handling all TX completions and to always ARM the IRQ
when we exit ->poll() with 0 budget.

Also, the logic to ACK the completion ring in case it is almost filled
with TX completions need to be adjusted to take care of the 0 budget
case, as discussed with Eric Dumazet <edumazet@google.com>
Reported-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(backported from commit 73f21c65)
[niv: Patch is for ubuntu/bnxt driver, adjusted file paths accordingly.]
Signed-off-by: Nivedita Singhvi <nivedita.singhvi@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

ubuntu/bnxt/bnxt.c

@@ -2006,8 +2006,11 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
 		if (TX_CMP_TYPE(txcmp) == CMP_TYPE_TX_L2_CMP) {
 			tx_pkts++;
 			/* return full budget so NAPI will complete. */
-			if (unlikely(tx_pkts > bp->tx_wake_thresh))
+			if (unlikely(tx_pkts > bp->tx_wake_thresh)) {
 				rx_pkts = budget;
+				raw_cons = NEXT_RAW_CMP(raw_cons);
+				break;
+			}
 		} else if ((TX_CMP_TYPE(txcmp) & 0x30) == 0x10) {
 			if (likely(budget))
 				rc = bnxt_rx_pkt(bp, bnapi, &raw_cons, &event);
@@ -2028,7 +2031,7 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
 		}
 		raw_cons = NEXT_RAW_CMP(raw_cons);
 
-		if (rx_pkts == budget)
+		if (rx_pkts && rx_pkts == budget)
 			break;
 	}
 
@@ -2156,8 +2159,12 @@ static int bnxt_poll(struct napi_struct *napi, int budget)
 	while (1) {
 		work_done += bnxt_poll_work(bp, bnapi, budget - work_done);
 
-		if (work_done >= budget)
+		if (work_done >= budget) {
+			if (!budget)
+				BNXT_CP_DB_REARM(cpr->cp_doorbell,
+						 cpr->cp_raw_cons);
 			break;
+		}
 
 		if (!bnxt_has_work(bp, cpr)) {
 #ifdef HAVE_NEW_NAPI_COMPLETE_DONE