nfp: opportunistically poll for reconfig result

If the reconfig was a quick update, we could have results available from
firmware within 200us.
Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -137,20 +137,37 @@ static bool nfp_net_reconfig_check_done(struct nfp_net *nn, bool last_check)
 	return false;
 }
 
-static int nfp_net_reconfig_wait(struct nfp_net *nn, unsigned long deadline)
+static bool __nfp_net_reconfig_wait(struct nfp_net *nn, unsigned long deadline)
 {
 	bool timed_out = false;
+	int i;
+
+	/* Poll update field, waiting for NFP to ack the config.
+	 * Do an opportunistic wait-busy loop, afterward sleep.
+	 */
+	for (i = 0; i < 50; i++) {
+		if (nfp_net_reconfig_check_done(nn, false))
+			return false;
+		udelay(4);
+	}
 
-	/* Poll update field, waiting for NFP to ack the config */
 	while (!nfp_net_reconfig_check_done(nn, timed_out)) {
-		msleep(1);
+		usleep_range(250, 500);
 		timed_out = time_is_before_eq_jiffies(deadline);
 	}
 
+	return timed_out;
+}
+
+static int nfp_net_reconfig_wait(struct nfp_net *nn, unsigned long deadline)
+{
+	if (__nfp_net_reconfig_wait(nn, deadline))
+		return -EIO;
+
 	if (nn_readl(nn, NFP_NET_CFG_UPDATE) & NFP_NET_CFG_UPDATE_ERR)
 		return -EIO;
 
-	return timed_out ? -EIO : 0;
+	return 0;
 }
 
 static void nfp_net_reconfig_timer(struct timer_list *t)