This is a note to let you know that I've just added the patch titled can: peak_usb: peak_usb_get_ts_time(): fix timestamp wrapping to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: can-peak_usb-peak_usb_get_ts_time-fix-timestamp-wrap.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 0da98b96d8b2cf72fe72e7602749b85ff4e8d817 Author: Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx> Date: Wed Oct 14 10:56:31 2020 +0200 can: peak_usb: peak_usb_get_ts_time(): fix timestamp wrapping [ Upstream commit ecc7b4187dd388549544195fb13a11b4ea8e6a84 ] Fabian Inostroza <fabianinostrozap@xxxxxxxxx> has discovered a potential problem in the hardware timestamp reporting from the PCAN-USB USB CAN interface (only), related to the fact that a timestamp of an event may precede the timestamp used for synchronization when both records are part of the same USB packet. However, this case was used to detect the wrapping of the time counter. This patch details and fixes the two identified cases where this problem can occur. Reported-by: Fabian Inostroza <fabianinostrozap@xxxxxxxxx> Signed-off-by: Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20201014085631.15128-1-s.grosjean@xxxxxxxxxxxxxxx Fixes: bb4785551f64 ("can: usb: PEAK-System Technik USB adapters driver core") Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_core.c b/drivers/net/can/usb/peak_usb/pcan_usb_core.c index 0b7766b715fd2..c844c6abe5fcd 100644 --- a/drivers/net/can/usb/peak_usb/pcan_usb_core.c +++ b/drivers/net/can/usb/peak_usb/pcan_usb_core.c @@ -130,14 +130,55 @@ void peak_usb_get_ts_time(struct peak_time_ref *time_ref, u32 ts, ktime_t *time) /* protect from getting time before setting now */ if (ktime_to_ns(time_ref->tv_host)) { u64 delta_us; + s64 delta_ts = 0; + + /* General case: dev_ts_1 < dev_ts_2 < ts, with: + * + * - dev_ts_1 = previous sync timestamp + * - dev_ts_2 = last sync timestamp + * - ts = event timestamp + * - ts_period = known sync period (theoretical) + * ~ dev_ts2 - dev_ts1 + * *but*: + * + * - time counters wrap (see adapter->ts_used_bits) + * - sometimes, dev_ts_1 < ts < dev_ts2 + * + * "normal" case (sync time counters increase): + * must take into account case when ts wraps (tsw) + * + * < ts_period > < > + * | | | + * ---+--------+----+-------0-+--+--> + * ts_dev_1 | ts_dev_2 | + * ts tsw + */ + if (time_ref->ts_dev_1 < time_ref->ts_dev_2) { + /* case when event time (tsw) wraps */ + if (ts < time_ref->ts_dev_1) + delta_ts = 1 << time_ref->adapter->ts_used_bits; + + /* Otherwise, sync time counter (ts_dev_2) has wrapped: + * handle case when event time (tsn) hasn't. + * + * < ts_period > < > + * | | | + * ---+--------+--0-+---------+--+--> + * ts_dev_1 | ts_dev_2 | + * tsn ts + */ + } else if (time_ref->ts_dev_1 < ts) { + delta_ts = -(1 << time_ref->adapter->ts_used_bits); + } - delta_us = ts - time_ref->ts_dev_2; - if (ts < time_ref->ts_dev_2) - delta_us &= (1 << time_ref->adapter->ts_used_bits) - 1; + /* add delay between last sync and event timestamps */ + delta_ts += (signed int)(ts - time_ref->ts_dev_2); - delta_us += time_ref->ts_total; + /* add time from beginning to last sync */ + delta_ts += time_ref->ts_total; - delta_us *= time_ref->adapter->us_per_ts_scale; + /* convert ticks number into microseconds */ + delta_us = delta_ts * time_ref->adapter->us_per_ts_scale; delta_us >>= time_ref->adapter->us_per_ts_shift; *time = ktime_add_us(time_ref->tv_host_0, delta_us);