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

[Jakub Kicinski]

From: Dirk van der Merwe <dirk.vanderme...@netronome.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.vanderme...@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.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