Re: [PATCH net 2/5] e1000e: do not cache the hwtstamp config before it is applied

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 28/10/2026 09:04, Linkui Xiao wrote:
> From: Linkui Xiao <xiaolinkui@kylinos.cn>
> 
> 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: stable@vger.kernel.org
> Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
> ---
>   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;
>   }
>   

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>