xilinx_can: fixed HW timestamping (fuzzy overflow checking)

diff --git a/petalinux/components/modules/xilinx_can/xilinx_can.c b/petalinux/components/modules/xilinx_can/xilinx_can.c
index 041260ef60047b9ca7dd3241ba4d7d4a3aadb36a..7a084fde7a1e526530b3580a4e018205f169e47f 100644 (file)
--- a/petalinux/components/modules/xilinx_can/xilinx_can.c
+++ b/petalinux/components/modules/xilinx_can/xilinx_can.c
@@ -483,6 +483,11 @@ static int xcan_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                else
                        nrollovers = floor((now_ktime - ref_ktime)/rollover_ktime)
                        frame_ktime = ref_ktime + nrollovers * rollover_ktime + to_ns(tsdelta)
+                       // must do fuzzy compare - the synchronization is not exact and so the frame_time
+                          may actually be before now_time and still not be in the next period, just because
+                          the latency between actual_frame_time and now_time may be lower than when
+                          it was for the first frame, about which it was assumed the two times happened in the same moment
+                          So compare it against half the period to be safe.
                        if frame_ktime > now_ktime
                                frame_ktime -= rollover_ktime
                set reference point (ref_ktime, ref_ts) = (frame_ktime, frame_ts) ??? cummulative loss of precision ? meybe not
@@ -503,29 +508,31 @@ static ktime_t xcan_timestamp2ktime(struct xcan_priv *priv, u16 ts, struct net_d
                frame_ktime = now_ktime;
                *tmdiffns = 0;
        } else {
+               s32 diff_us;
                u16 tsdelta = (ts - ref->ts) & 0xFFFF;
 #define TS2NS(ts) div_u64((ts) * (u64)1000000000, freq)
-               // nrollovers = nowdelta / rollover_ns
-               // nrollovers = nowdelta / (65536 * 1000000000 / freq)
-               // nrollovers = nowdelta * freq / (65536 * 1000000000)
                s64 rollover_ns = TS2NS(65536);
                ktime_t nowdelta = ktime_sub(now_ktime, ref->ktime);
-               u32 nrollovers = ktime_divns(nowdelta, rollover_ns);
-               //u32 nrollovers = ktime_divns(ns_to_ktime(ktime_to_ns(nowdelta) * freq), 65536 * 1000000000ULL);
-               
+               s64 nrollovers = ktime_divns(nowdelta, rollover_ns);
+
                frame_ktime = ktime_add_ns(ref->ktime, nrollovers * rollover_ns + TS2NS(tsdelta));
-               //frame_ktime = ktime_add_ns(ref->ktime, div_u64(((u64)nrollovers * 65536 + tsdelta) * 1000000000, freq));
-               if (ktime_after(frame_ktime, now_ktime)) {
+
+               diff_us = ktime_to_us(ktime_sub(now_ktime, frame_ktime));
+               diff_us = diff_us < 0 ? -diff_us : diff_us;
+
+               /* If the (magnitude of) delay is greater than half */
+               /* the period, the frame arrived in previous period */
+               if (diff_us*1000*2 > rollover_ns) {
                        frame_ktime = ktime_sub_ns(frame_ktime, rollover_ns);
                }
-               /*netdev_warn(netdev, "TS: ftime = %llu, delay = %lld us%s; hwtime = %hu, nrollovers = %u, "
-                                       "tsdelta = %hu, freq = %u, ref->ktime = %llu, ref->ts = %hu, now_ktime = %llu",
+               /*
+               netdev_warn(netdev, "TS: ftime = %llu, delay = %lld us; hwtime = %hu, nrollovers = %llu, "
+                                       "now_ktime = %llu",
                                        ktime_to_ns(frame_ktime),
                                        ktime_to_us(ktime_sub(now_ktime, frame_ktime)),
-                                       corr ? ", corr" : "",
                                        ts,
-                                       nrollovers, tsdelta, freq, ref->ktime, ref->ts, now_ktime);*/
-               
+                                       nrollovers, ktime_to_ns(now_ktime));
+               */
                *tmdiffns = ktime_to_ns(ktime_sub(now_ktime, frame_ktime)) & 0xFFFFFFFF;
 #undef TS2NS
        }
@@ -598,8 +605,11 @@ static int xcan_rx(struct net_device *ndev)
        /* DW1/DW2 must always be read to remove message from RXFIFO */
        data[0] = priv->read_reg(priv, XCAN_RXFIFO_DW1_OFFSET);
        data[1] = priv->read_reg(priv, XCAN_RXFIFO_DW2_OFFSET);
-       //data[1] = tmdiffns; // DBG
-
+       /*
+       data[0] = (data[0] & 0xFFFF0000) | (u16)((s16)(rawts - priv->ref_timepoint.ts)); // DBG
+       data[1] = tmdiffns; // DBG
+       cf->can_dlc = 8; // DBG
+       */
        if (!(cf->can_id & CAN_RTR_FLAG)) {
                /* Change Xilinx CAN data format to socketCAN data format */
                if (cf->can_dlc > 0)