[PATCH net v3] net: stmmac: propagate PTP addend and system time programming errors

[Anirudh Srinivasan]

Hi Lorenzo,

On Mon, Oct 5, 2026 at 4:53 PM Lorenzo Bianconi
<lorenzo.bianconi at oss.qualcomm.com> wrote:
>
> > On Tue, Sep 29, 2026 at 03:10:11PM +0200, Lorenzo Bianconi wrote:
> > > stmmac_update_subsecond_increment() ignores the error returned by
> > > stmmac_config_addend(), and stmmac_init_tstamp_counter() discards the
> > > addend and system time programming errors, always returning success. A
> > > failure to program the addend (PTP_TCR_TSADDREG) or to initialize the
> > > system time counter (PTP_TCR_TSINIT) is therefore silently swallowed,
> > > leaving the hardware timestamp counter in a non-running or partially
> > > configured state while the driver keeps operating as if timestamping
> > > were up. This matters for TAPRIO/EST offloading, which derives the gate
> > > base time from the hardware timestamp counter.
> > >
> > > The same hooks are also called from the PHC callbacks: settime64 and
> > > adjfine drop the error and report success to clock_settime() and
> > > clock_adjtime(), so a dead PTP reference clock goes unnoticed by
> > > ptp4l/phc2sys.
> > >
> > > Return error codes from stmmac_update_subsecond_increment(),
> > > stmmac_init_tstamp_counter(), stmmac_dl_ts_coarse_set() and the
> > > settime64/adjfine callbacks instead of silently returning success. On
> > > failure, roll back the partially applied configuration so the hardware
> > > and the driver bookkeeping stay consistent, and report the reason
> > > through the devlink extack. Also guard against a zero sub-second
> > > increment, which would otherwise divide by zero when computing the
> > > addend.
> > >
> > > Reset the persistent timestamping state (hwts_tx_en, hwts_rx_en,
> > > tstamp_config, systime_flags and tsfupdt_coarse) when (re)initializing
> > > timestamping, so a failed init does not leave TX/RX timestamping
> > > enabled on a counter that never started.
> > >
> > > Fixes: cc4c9001ce31 ("net: stmmac: Switch stmmac_hwtimestamp to generic HW Interface Helpers")
> > > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi at oss.qualcomm.com>
> > > ---
> > > Changes in v3:
> > > - Do not run stmmac_config_addend() in
> > >   stmmac_update_subsecond_increment() error path.
> > > - Return error from stmmac_adjust_freq() and stmmac_set_time().
> > > - Reset hw ts configuration in stmmac_init_timestamping().
> > > - Link to v2: https://lore.kernel.org/r/20260924-stmmac-ptp-added-systime-error-v2-1-beb2a6b5f866@oss.qualcomm.com
> > >
> > > Changes in v2:
> > > - Initialize sec_inc to 0 in stmmac_restore_subsecond_increment()
> > >   routine.
> > > - Link to v1: https://lore.kernel.org/r/20260920-stmmac-ptp-added-systime-error-v1-1-8ac9e7a3fce2@oss.qualcomm.com
> > > ---
> > >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 106 ++++++++++++++++------
> > >  drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c  |  10 +-
> > >  2 files changed, 84 insertions(+), 32 deletions(-)
> >
> > Hello, I'm noticing that after this patch was merged into linux-next,
> > boot seems to hang when ip=dhcp is used because ethernet isn't working
> > on the TH1520 Lichee Pi 4a. These lines get printed in a loop over and
> > over
> >
> > IP-Config: end0 hardware address 72:ca:a8:eb:27:[   24.872982] thead-dwmac ffe7070000.ethernet end0: Register MEM_TYPE_PAGE_POOL RxQ-0
> > f2 mtu 1500 DHCP
> > [   24.900412] thead-dwmac ffe7070000.ethernet end0: PHY [stmmac-0:01] driver [RTL8211F Gigabit Ethernet] (irq=POLL)
> > [   24.912780] dwmac1000: Master AXI performs any burst length
> > [   24.912801] thead-dwmac ffe7070000.ethernet end0: No Safety Features support found
> > [   25.010229] thead-dwmac ffe7070000.ethernet end0: PTP init failed
> > SIOCSIFFLAGS: Connection timed out
>
> Hi Anirudh,
>
> based on the reported error, stmmac_init_tstamp_counter() fails with
> -ETIMEDOUT. In particular this can occurs if:
>
> stmmac_init_tstamp_counter()
>  -> stmmac_update_subsecond_increment() -> stmmac_config_addend() -> -ETIMEDOUT
>  -> stmmac_init_systime() -> -ETIMEDOUT
>
> I guess we should understand which one is failing and why it is failing.

It seems like both are timing out, both config_addend
(PTP_TCR_TSADDREG) and init_systime (PTP_TCR_TSINIT).

Regards
Anirudh Srinivasan