net: stmmac: retain PTP clock time during SIOCSHWTSTAMP ioctls
[ Upstream commit a6da2bbb ] 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. Fixes: 92ba6888 ("stmmac: add the support for PTP hw clock driver") Reported-by:Michael Olbrich <m.olbrich@pengutronix.de> Signed-off-by:
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