Re: [PATCH net] ixgbe: fix timestamp configuration code

[Simon Horman <horms@kernel.org>]

On Wed, Aug 23, 2023 at 11:15:37PM +0100, Vadim Fedorenko wrote:
> The commit in fixes introduced flags to control the status of hardware
> configuration while processing packets. At the same time another structure
> is used to provide configuration of timestamper to user-space applications.
> The way it was coded makes this structures go out of sync easily. The
> repro is easy for 82599 chips:
> 
> [root@hostname ~]# hwstamp_ctl -i eth0 -r 12 -t 1
> current settings:
> tx_type 0
> rx_filter 0
> new settings:
> tx_type 1
> rx_filter 12
> 
> The eth0 device is properly configured to timestamp any PTPv2 events.
> 
> [root@hostname ~]# hwstamp_ctl -i eth0 -r 1 -t 1
> current settings:
> tx_type 1
> rx_filter 12
> SIOCSHWTSTAMP failed: Numerical result out of range
> The requested time stamping mode is not supported by the hardware.
> 
> The error is properly returned because HW doesn't support all packets
> timestamping. But the adapter->flags is cleared of timestamp flags
> even though no HW configuration was done. From that point no RX timestamps
> are received by user-space application. But configuration shows good
> values:
> 
> [root@hostname ~]# hwstamp_ctl -i eth0
> current settings:
> tx_type 1
> rx_filter 12
> 
> Fix the issue by applying new flags only when the HW was actually
> configured.
> 
> Fixes: a9763f3cb54c ("ixgbe: Update PTP to support X550EM_x devices")
> Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>

Reviewed-by: Simon Horman <horms@kernel.org>