Messages in this thread | | | From | Vladimir Oltean <> | Subject | Re: [PATCH net] net: stmmac: retain PTP clock time during SIOCSHWTSTAMP ioctls | Date | Sun, 21 Nov 2021 17:46:36 +0000 |
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On Fri, Nov 19, 2021 at 07:58:51PM -0800, Jakub Kicinski wrote: > On Sat, 20 Nov 2021 01:05:42 +0200 Vladimir Oltean wrote: > > Currently, when user space emits SIOCSHWTSTAMP ioctl calls such as > > enabling/disabling timestamping or changing filter settings, the driver > > reads the current CLOCK_REALTIME value and programming this into the > > NIC's hardware clock. This might be necessary during system > > initialization, but at runtime, when the PTP clock has already been > > synchronized to a grandmaster, a reset of the timestamp settings might > > result in a clock jump. Furthermore, if the clock is also controlled by > > phc2sys in automatic mode (where the UTC offset is queried from ptp4l), > > that UTC-to-TAI offset (currently 37 seconds in 2021) would be > > temporarily reset to 0, and it would take a long time for phc2sys to > > readjust so that CLOCK_REALTIME and the PHC are apart by 37 seconds > > again. > > > > To address the issue, we introduce a new function called > > stmmac_init_tstamp_counter(), which gets called during ndo_open(). > > It contains the code snippet moved from stmmac_hwtstamp_set() that > > manages the time synchronization. Besides, the sub second increment > > configuration is also moved here since the related values are hardware > > dependent and runtime invariant. > > > > Furthermore, the hardware clock must be kept running even when no time > > stamping mode is selected in order to retain the synchronized time base. > > That way, timestamping can be enabled again at any time only with the > > need to compensate the clock's natural drifting. > > > > As a side effect, this patch fixes the issue that ptp_clock_info::enable > > can be called before SIOCSHWTSTAMP and the driver (which looks at > > priv->systime_flags) was not prepared to handle that ordering. > > Makes build fail: > > ERROR: modpost: "stmmac_init_tstamp_counter" [drivers/net/ethernet/stmicro/stmmac/stmmac-platform.ko] undefined!
You're right, I'm missing an EXPORT_SYMBOL, thanks.
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