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

[Jacob Keller <jacob.e.keller@intel.com>]

On 10/28/2026 2:04 AM, 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.
> 

Any idea why this got marked as patch 2 out of 5? This doesn't appear on
either netdev or iwl with any other patches.

I'm going ahead and applying it to Intel Wired LAN regardless, since the
fix looks good.

Thanks,
Jake

> 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;
>  }
>