Ping
Fabián Antonio Inostroza Paredes
Ingeniero Civil Electrónico
Fono: +56962243036
On Wed, Sep 2, 2020 at 7:44 AM Stéphane Grosjean
<s.grosjean@xxxxxxxxxxxxxxx> wrote:
>
> Hi Marc,
>
> Any news about that patch?
>
> ---
> Stéphane Grosjean
> PEAK-System France
> 132, rue André Bisiaux
> F-54320 MAXEVILLE
> Tél : +(33) 9.72.54.51.97
>
>
> De : Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
> Envoyé : mardi 28 juillet 2020 11:07
> À : linux-can Mailing List <linux-can@xxxxxxxxxxxxxxx>
> Cc : Stéphane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
> Objet : [PATCH] can/peak_usb: fix timestamp wrapping
>
> 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.
>
> Signed-off-by: Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
> ---
> drivers/net/can/usb/peak_usb/pcan_usb_core.c | 51 ++++++++++++++++++--
> 1 file changed, 46 insertions(+), 5 deletions(-)
>
> 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 0b7766b715fd..267ddc18ed51 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);
> --
> 2.25.1
>
>
> --
> PEAK-System Technik GmbH
> Sitz der Gesellschaft Darmstadt - HRB 9183
> Geschaeftsfuehrung: Alexander Gach / Uwe Wilhelm
> Unsere Datenschutzerklaerung mit wichtigen Hinweisen
> zur Behandlung personenbezogener Daten finden Sie unter
> www.peak-system.com/Datenschutz.483.0.html
>
> --
> PEAK-System Technik GmbH
> Sitz der Gesellschaft Darmstadt - HRB 9183
> Geschaeftsfuehrung: Alexander Gach / Uwe Wilhelm
> Unsere Datenschutzerklaerung mit wichtigen Hinweisen
> zur Behandlung personenbezogener Daten finden Sie unter
> www.peak-system.com/Datenschutz.483.0.html
