Re: Flexcan - timestamp from message buffer to userspace

[Martin Kozusky <mkozusky@kkmicro.cz>]

Dne 21.10.2013 10:11, Wolfgang Grandegger napsal(a):
> My previous mail went out to early, sorry... completing it now...
>
>
>
> On Mon, 21 Oct 2013 10:00:28 +0200, Wolfgang Grandegger
>
> <wg@grandegger.com> wrote:
>
>> On Mon, 21 Oct 2013 08:54:30 +0200, Martin Kozusky <mkozusky@kkmicro.cz>
>
>> wrote:
>
>>> Dne 18.10.2013 16:42, Oliver Hartkopp napsal(a):
>
>>>> On 18.10.2013 12:55, Martin Kozusky wrote:
>
>>>>>
>
>>>>> Dne 18.10.2013 11:56, Martin Kozusky napsal(a):
>
>>>>>> Hello,
>
>>>>>> is there any official way how to read timestamp from flexcans
>
> message
>
>>>>>> buffer?
>
>>>>>> I see there is a macro defined FLEXCAN_MB_CNT_TIMESTAMP in
>
> flexcan.c,
>
>>>>>> but not used.
>
>>>>>> I would modify function flecan_read_fifo like
>
>>>>>>
>
>>>>>> + u32 timestamp = FLEXCAN_MB_CNT_TIMESTAMP(reg_ctrl);
>
>>>>>
>
>>>>> sorry, u32 should be just u16
>
>>>>>
>
>>>>>> but what to do with timestamp variable next and how to read it in
>
>>>>>> userspace? :) I could change structure can_frame and add  u32
>
>> timestamp
>
>>>>> also u16, not u32
>
>>>>>
>
>>>>>> into it, but it wouldn't be very nice hack I think.
>
>>>>>>
>
>>>>>> BTW: is timestamp read with SO_TIMESTAMP  actualy taken when CAN
>
>>>>>> message
>
>>>>>> arrives?
>
>>>>>>
>
>>>>
>
>>>> Hello Martin,
>
>>>>
>
>>>> with SO_TIMESTAMP you get the system timestamp in nanosec resolution.
>
>>>>
>
>>>> It is set at the time when the CAN frame is pushed to the network
>
> layer
>
>>>> by
>
>>>> the CAN drivers interrupt routine.
>
>>>>
>
>>>> See net_timestamp_check() in netif_rx():
>
>>>>
>
>>>>
>
>>
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/core/dev.c#n3228
>
>>> Hello Oliver,
>
>>> I'm already using SO_TIMESTAMP with recvmmsg so may be I should switch
>
>>> to SO_TIMESTAMPNS for better times, right?
>
>>>
>
>>>> You may get this timestamp via ioctl() or recvmsg().
>
>>>>
>
>>>> To pass hardware timestamps there's some infrastructure for ethernet
>
>>>> devices in the
>
>>>> mainlaine kernel, which is configured with "ethtool":
>
>>>>
>
>>>>      ethtool -T|--show-time-stamping DEVNAME    Show time stamping
>
>>>>      capabilities
>
>>>>
>
>>>> See details at
>
>>>>
>
>>>>
>
>>
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/timestamping.txt
>
>>>>
>
>>>> And some example source code at
>
>>>>
>
>>>>
>
>>
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/timestamping/timestamping.c
>
>>>>
>
>>>> There needs to be added some infrastructure to the network devices to
>
>>>> query
>
>>>> and configure the timestamping possibilities.
>
>>>>
>
>>>> This is currently missing for CAN devices ...
>
>>>>
>
>>>> Even if I moved a wrongly assigned hardware timestamp to another place
>
>>>> here:
>
>>>>
>
>>>>
>
>>
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/net/can/usb/peak_usb?id=c9faaa09e2a1335678f09c70a0d0eda095564bab
>
>>>>
>
>>>> the rest of the hardware timestamping (& configuration) is still
>
>> missing.
>
>
>
> Supporting SIOCSHWTSTAMP seem the right way to go.
>
>
>
>>>
>
>>> So I could just do
>
>>>
>
>>>    struct skb_shared_hwtstamps *hwts;
>
>>>    hwts = skb_hwtstamps(skb);
>
>
>
> Most drivers do as well:
>
>
>
>   memset(hwts, 0, sizeof(*hwts));
>
>
>
>>>    hwts->hwtstamp = FLEXCAN_MB_CNT_TIMESTAMP(reg_ctrl);
>
>
>
> This should assign a proper ktime. [nm]s_to_ktime() may help.

But value read from registers is just 16bit value having nothing to do 
with real time. But now when I see the ns_to_ktime function, it will 
just assign my 16bit value to .tv64 union member, ok I will use it.

But I see another problem here:
  flexcan registers are read in function flexcan_read_fifo but I need to 
know the timestamp in function flexcan_read_frame, how do I transfer it 
from there?

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/net/can/flexcan.c#n519

Should I just create some global variable in flexcan.c and store the 
16bit value into it and then use it?


>
>>> in  flecan_read_fifo ?
>
>>>
>
>>> And then how to read it?
>
>>
>
>> See:
>
>>
>
>>
>
> http://lxr.free-electrons.com/source/Documentation/networking/timestamping/
>
>
>
> This also shows how to do read the timestamp.
>


So you mean this setup:


   memset(&hwtstamp, 0, sizeof(hwtstamp));
   strncpy(hwtstamp.ifr_name, interface, sizeof(hwtstamp.ifr_name));
   hwtstamp.ifr_data = (void *)&hwconfig;
   memset(&hwconfig, 0, sizeof(hwconfig));
   hwconfig.tx_type = HWTSTAMP_TX_OFF;
   hwconfig.rx_filter = HWTSTAMP_FILTER_ALL;
   hwconfig_requested = hwconfig;
   if (ioctl(sock, SIOCSHWTSTAMP, &hwtstamp) < 0) {
      if ((errno == EINVAL || errno == ENOTSUP) &&
          hwconfig_requested.tx_type == HWTSTAMP_TX_OFF &&
          hwconfig_requested.rx_filter == HWTSTAMP_FILTER_NONE)
        printf("SIOCSHWTSTAMP: disabling hardware time stamping not 
possible\n");
      else
        bail("SIOCSHWTSTAMP");
   }
  printf("SIOCSHWTSTAMP: tx_type %d requested, got %d; rx_filter %d 
requested, got %d\n",
  hwconfig_requested.tx_type, hwconfig.tx_type,
  hwconfig_requested.rx_filter, hwconfig.rx_filter);


and read from this cmsg_type:

case SO_TIMESTAMPING: {
   struct scm_timestamping *stamp =
   (struct scm_timestamping *)CMSG_DATA(cmsg);
     printf("SO_TIMESTAMPING ");
     printf("HW raw %ld.%09ld",
      (long)stamp->hwtimeraw->tv_sec,
      (long)stamp->hwtimeraw->tv_nsec);
  break;
}


or did I forget something?

Thank you,
Martin

>
>>>
>
>>> Or will it be easier for me just to change can_frame structure? :)
>
>>
>
>> No.
>
>
>
> Please use the forseen interface.
>
>
>
> Wolfgang
> --
> To unsubscribe from this list: send the line "unsubscribe linux-can" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>