netdev - [PATCH net-next 1/4] nfp: opportunistically poll for reconfig result

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Date:   Thu, 11 Apr 2019 20:27:04 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        alexei.starovoitov@...il.com,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net-next 1/4] nfp: opportunistically poll for reconfig result

From: Dirk van der Merwe <dirk.vandermerwe@...ronome.com>

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@...ronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 .../ethernet/netronome/nfp/nfp_net_common.c   | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index bde9695b9f8a..60f2da438990 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/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)
-- 
2.21.0