[Intel-wired-lan] [PATCH iwl-net 3/3] ice: restore timestamp configuration after device reset

[Pucha, HimasekharX Reddy]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces at osuosl.org> On Behalf Of Jacob Keller
> Sent: Saturday, November 4, 2023 5:17 AM
> To: Nguyen, Anthony L <anthony.l.nguyen at intel.com>
> Cc: Keller, Jacob E <jacob.e.keller at intel.com>; netdev at vger.kernel.org; Intel Wired LAN <intel-wired-lan at lists.osuosl.org>; Brandeburg, Jesse <jesse.brandeburg at intel.com>
> Subject: [Intel-wired-lan] [PATCH iwl-net 3/3] ice: restore timestamp configuration after device reset
>
> The driver calls ice_ptp_cfg_timestamp() during ice_ptp_prepare_for_reset()
> to disable timestamping while the device is resetting. This operation
> destroys the user requested configuration. While the driver does call
> ice_ptp_cfg_timestamp in ice_rebuild() to restore some hardware settings
> after a reset, it unconditionally passes true or false, resulting in
> failure to restore previous user space configuration.
>
> This results in a device reset forcibly disabling timestamp configuration
> regardless of current user settings.
>
> This was not detected previously due to a quirk of the LinuxPTP ptp4l
> application. If ptp4l detects a missing timestamp, it enters a fault state
> and performs recovery logic which includes executing SIOCSHWTSTAMP again,
> restoring the now accidentally cleared configuration.
>
> Not every application does this, and for these applications, timestamps
> will mysteriously stop after a PF reset, without being restored until an
> application restart.
>
> Fix this by replacing ice_ptp_cfg_timestamp() with two new functions:
>
> 1) ice_ptp_disable_timestamp_mode() which unconditionally disables the
>    timestamping logic in ice_ptp_prepare_for_reset() and ice_ptp_release()
> 
> 2) ice_ptp_restore_timestamp_mode() which calls
>    ice_ptp_restore_tx_interrupt() to restore Tx timestamping configuration,
>    calls ice_set_rx_tstamp() to restore Rx timestamping configuration, and
>    issues an immediate TSYN_TX interrupt to ensure that timestamps which
>    may have occurred during the device reset get processed.
>
> Modify the ice_ptp_set_timestamp_mode to directly save the user
> configuration and then call ice_ptp_restore_timestamp_mode. This way, reset
> no longer destroys the saved user configuration.
>
> This obsoletes the ice_set_tx_tstamp() function which can now be safely
> removed.
>
> With this change, all devices should now restore Tx and Rx timestamping
> functionality correctly after a PF reset without application intervention.
>
> Fixes: 77a781155a65 ("ice: enable receive hardware timestamping")
> Fixes: ea9b847cda64 ("ice: enable transmit timestamps for E810 devices")
> Signed-off-by: Jacob Keller <jacob.e.keller at intel.com>
> Reviewed-by: Jesse Brandeburg <jesse.brandeburg at intel.com>
>  ---
>  drivers/net/ethernet/intel/ice/ice_main.c | 12 +---
>  drivers/net/ethernet/intel/ice/ice_ptp.c  | 76 ++++++++++++++---------
>  drivers/net/ethernet/intel/ice/ice_ptp.h  |  5 +-
>  3 files changed, 52 insertions(+), 41 deletions(-)
>

Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha at intel.com> (A Contingent worker at Intel)