AW: ATH9k_HTC mactime vs. system timestamp (timeval)

Steger, Marco Marco.Steger at v2c2.at
Thu Mar 19 04:54:32 PDT 2015


Hi,

thank you for your help. This is very interesting and I will take this into account.

 On additional question: I used the ath9k_htc_rx_status struct to get the receive time (I found in a header file that rx_status->mactime ts contains the time when the beginning of the data frame is received). The ath9k_htc_tx_ctl struct seems to be the equivalent on the sender side. I will try to use this to get the time when a frame is sent out. 
Can one of you give me a hint how to do that?!

Best regards,
Marco

>-----Ursprüngliche Nachricht-----
>Von: adrian.chadd at gmail.com [mailto:adrian.chadd at gmail.com] Im Auftrag von
>Adrian Chadd
>Gesendet: Mittwoch, 18. März 2015 17:05
>An: Steger, Marco
>Cc: ath9k_htc_fw at lists.infradead.org
>Betreff: Re: ATH9k_HTC mactime vs. system timestamp (timeval)
>
>Hi,
>
>They're different because the MAC timestamp is based on whatever clock the
>MAC is synched to.
>
>In hostap mode it'll be itself, and no, there's no requirement for it to be synched
>against the system timestamp.
>
>In station mode it'll sync the MAC timestamp against the hostap timestamp.
>
>The 802.11 timestamps are not supposed to be synched against the system
>timestamp - they're designed for timekeeping inside a BSS to synchronise things
>like power save, etc.
>
>
>
>-a
>
>
>On 18 March 2015 at 01:27, Steger, Marco <Marco.Steger at v2c2.at> wrote:
>> Hi all,
>>
>> I have a small question about the mactime timestamp. I want to get an
>accurate timestamp for the point in time when the packet is received (driver/hw).
>>
>> Therefore, I took a look on the ath9k_rx_prepare.c file. In the function
>ath9k_rx_prepare the mactime is set:
>> rx_status->mactime = be64_to_cpu(rxstatus->rs_tstamp);
>>
>> When I print this timestamp and compare it with the Debian/linux system
>timestamp (timeval) I recognized that:
>> * both are (should be) 64bit values
>> * but they are different:
>>  [ 2141.033905] TS: timeval-ts [1426665454085102] mactime-ts
>> [688414257]  [ 2141.034290] TS: timeval-ts [1426665454085613]
>> mactime-ts [688414675]  [ 2141.034697] TS: timeval-ts
>> [1426665454086024] mactime-ts [688415074]  [ 2141.035071] TS:
>> timeval-ts [1426665454086420] mactime-ts [688415456]  [ 2141.035442]
>> TS: timeval-ts [1426665454086797] mactime-ts [688415827]  [
>> 2141.035817] TS: timeval-ts [1426665454087170] mactime-ts [688416203]
>> [ 2141.036173] TS: timeval-ts [1426665454087544] mactime-ts
>> [688416569]  [ 2141.036566] TS: timeval-ts [1426665454087915]
>> mactime-ts [688416953]  [ 2141.036943] TS: timeval-ts
>> [1426665454088301] mactime-ts [688417342]  [ 2141.037345] TS:
>> timeval-ts [1426665454088682] mactime-ts [688417745]
>>
>> So I think there must/should be an easy way to get a system ts out of the
>mactime ts but I don't know how at the moment.
>>
>> Would be great if you can help me here!
>>
>> Best regards,
>> Marco
>>
>>
>> Dipl.-Ing. Marco Steger
>> Junior Researcher
>> Area Electrics/Electronics & Software (Area E)
>>
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