[Intel-wired-lan] [PATCH iwl-next v3 0/5] ice: Improve miscellaneous interrupt code

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

This series improves the driver's use of the threaded IRQ and the
communication between ice_misc_intr() and the ice_misc_intr_thread_fn()
which was previously introduced by commit 1229b33973c7 ("ice: Add low
latency Tx timestamp read").

First, a new custom enumerated return value is used instead of a boolean for
ice_ptp_process_ts(). This significantly reduces the cognitive burden when
reviewing the logic for this function, as the expected action is clear from
the return value name.

Second, the unconditional loop in ice_misc_intr_thread_fn() is removed,
replacing it with a write to the Other Interrupt Cause register. This causes
the MAC to trigger the Tx timestamp interrupt again. This makes it possible
to safely use the ice_misc_intr_thread_fn() to handle other tasks beyond
just the Tx timestamps. It is also easier to reason about since the thread
function will exit cleanly if we do something like disable the interrupt and
call synchronize_irq().

Third, refactor the handling for external timestamp events to use the
miscellaneous thread function. This resolves an issue with the external
time stamps getting blocked while processing the periodic work function
task.

Fourth, a simplification of the ice_misc_intr() function to always return
IRQ_WAKE_THREAD, and schedule the ice service task in the
ice_misc_intr_thread_fn() instead.

Finally, the Other Interrupt Cause is kept disabled over the thread function
processing, rather than immediately re-enabled.

Special thanks to Michal Schmidt for the careful review of the series and
pointing out my misunderstandings of the kernel IRQ code. It has been
determined that the race outlined as being fixed in previous series was
actually introduced by this series itself, which I've since corrected.

Changes since v2:
* heavily re-ordered patches for clarity and a better flow of implementation
* used atomic bits when communicating between ice_misc_intr() and
  ice_misc_intr_thread_fn()
* re-wrote commit messages to improve clarity and remove mistakes about how
  threaded IRQs work.

Jacob Keller (3):
  ice: introduce ICE_TX_TSTAMP_WORK enumeration
  ice: trigger PFINT_OICR_TSYN_TX interrupt instead of polling
  ice: do not re-enable miscellaneous interrupt until thread_fn
    completes

Karol Kolacinski (2):
  ice: handle extts in the miscellaneous interrupt thread
  ice: always return IRQ_WAKE_THREAD in ice_misc_intr()

 drivers/net/ethernet/intel/ice/ice.h      |  7 +++
 drivers/net/ethernet/intel/ice/ice_main.c | 47 +++++++++++------
 drivers/net/ethernet/intel/ice/ice_ptp.c  | 62 ++++++++++++-----------
 drivers/net/ethernet/intel/ice/ice_ptp.h  | 16 ++++--
 4 files changed, 84 insertions(+), 48 deletions(-)


base-commit: f08ff053a47a51d4f391d407bdda6adb4e7ed499
-- 
2.40.0.471.gbd7f14d9353b

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