ENGR00309055 net: fec_ptp: optimize 1588 convergent performance

1588 convergence process (setup time about 15s) is not ideal:
Applied a time jump on the reference master which causes both slaves
to apply a time jump as well and then synchronize back to the nanoseconds.

Optimize the 1588 adjust algorithm to get better convergent action.

Signed-off-by: Fugang Duan <B38611@freescale.com>
(cherry picked from commit 46a727f7ef469ae7c77c3458efd8a0de2396c360)

1 files changed, 18 insertions, 33 deletions

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 03e10de40e94..93e55bc441a6 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -473,8 +473,7 @@ static void fec_handle_ptpdrift(struct fec_enet_private *priv,
         struct ptp_set_comp *comp, struct ptp_time_correct *ptc)
 {
         u32 ndrift;
-        u32 i, adj_inc, adj_period;
-        u32 tmp_current, tmp_winner;
+        u32 i;
         u32 ptp_ts_clk, ptp_inc;
 
         ptp_ts_clk = clk_get_rate(priv->clk_ptp);
@@ -486,40 +485,26 @@ static void fec_handle_ptpdrift(struct fec_enet_private *priv,
                 ptc->corr_inc = 0;
                 ptc->corr_period = 0;
                 return;
-        } else if (ndrift >= ptp_ts_clk) {
-                ptc->corr_inc = (u32)(ndrift / ptp_ts_clk);
-                ptc->corr_period = 1;
-                return;
-        } else {
-                tmp_winner = 0xFFFFFFFF;
-                adj_inc = 1;
-
-                if (ndrift > (ptp_ts_clk / ptp_inc)) {
-                        adj_inc = ptp_inc / FEC_PTP_SPINNER_2;
-                } else if (ndrift > (ptp_ts_clk /
-                        (ptp_inc * FEC_PTP_SPINNER_4))) {
-                        adj_inc = ptp_inc / FEC_PTP_SPINNER_4;
-                        adj_period = FEC_PTP_SPINNER_2;
-                } else {
-                        adj_inc = FEC_PTP_SPINNER_4;
-                        adj_period = FEC_PTP_SPINNER_4;
-                }
+        }
 
-                for (i = 1; i < adj_inc; i++) {
-                        tmp_current = (ptp_ts_clk * i) % ndrift;
-                        if (tmp_current == 0) {
-                                ptc->corr_inc = i;
-                                ptc->corr_period = (u32)((ptp_ts_clk *
-                                                adj_period * i) / ndrift);
-                                break;
-                        } else if (tmp_current < tmp_winner) {
-                                ptc->corr_inc = i;
-                                ptc->corr_period = (u32)((ptp_ts_clk *
-                                                adj_period * i) / ndrift);
-                                tmp_winner = tmp_current;
-                        }
+        for (i = 1; i <= ptp_inc; i++) {
+                if (((i * FEC_T_PERIOD_ONE_SEC) / ndrift) > ptp_inc) {
+                        ptc->corr_inc = i;
+                        ptc->corr_period = ((i * FEC_T_PERIOD_ONE_SEC) /
+                                                (ptp_inc * ndrift));
+                        break;
                 }
         }
+
+        /* not found ? */
+        if (i > ptp_inc) {
+                /*
+                 * set it to high value - double speed
+                 * correct in every clock step.
+                 */
+                ptc->corr_inc = ptp_inc;
+                ptc->corr_period = 1;
+        }
 }
 
 static void fec_set_drift(struct fec_enet_private *priv,