> -----Original Message-----
> From: Linkui Xiao <[email protected]>
> Sent: Wednesday, October 28, 2026 10:05 AM
> To: Nguyen, Anthony L <[email protected]>; Kitszel, Przemyslaw
> <[email protected]>; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]
> Cc: [email protected]; [email protected]; linux-
> [email protected]; Linkui Xiao <[email protected]>;
> [email protected]
> Subject: [PATCH net 2/5] e1000e: do not cache the hwtstamp config before
> it is applied
>
> From: Linkui Xiao <[email protected]>
>
> e1000e_config_hwtstamp() stores the requested configuration in
> adapter->hwtstamp_config right after the rx filter has been
> translated, but the two register writes that follow are verified by
> reading the registers back and each of them can fail with -EAGAIN.
>
> When one of them does, the driver is left holding a configuration the
> hardware never accepted:
>
> - e1000e_hwtstamp_get() hands it back to user space, so an
> application that reads the configuration back is told that
> hardware time stamping is in effect while it is not;
>
> - e1000e_systim_reset() re-applies it after every reset, including
> the ones the watchdog triggers, and keeps failing;
>
> - e1000_watchdog() starts polling TSYNCRXCTL_VALID for the cached rx
> filter, and e1000_xmit_frame() still parks skbs that ask for a Tx
> time stamp because it only looks at FLAG_HAS_HW_TIMESTAMP, so they
> are eventually dropped by e1000e_tx_hwtstamp_work() with a
> "clearing Tx timestamp hang" warning.
>
> Cache the configuration only once both registers have been verified, so
> that adapter->hwtstamp_config always describes what the hardware is
> programmed with.
>
> Fixes: 62d7e3a2d006 ("e1000e: Validate hwtstamp_config completely before
> applying it")
> Cc: [email protected]
> Signed-off-by: Linkui Xiao <[email protected]>
> ---
> drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
> b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 35f5590228eb..7ae33273734f 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -3715,8 +3715,6 @@ static int e1000e_config_hwtstamp(struct
> e1000_adapter *adapter,
> return -ERANGE;
> }
>
> - adapter->hwtstamp_config = *config;
> -
> /* enable/disable Tx h/w time stamping */
> regval = er32(TSYNCTXCTL);
> regval &= ~E1000_TSYNCTXCTL_ENABLED;
> @@ -3763,6 +3761,8 @@ static int e1000e_config_hwtstamp(struct
> e1000_adapter *adapter,
> er32(RXSTMPH);
> er32(TXSTMPH);
>
> + adapter->hwtstamp_config = *config;
> +
> return 0;
> }
>
> --
> 2.25.1
Reviewed-by: Aleksandr Loktionov <[email protected]>
