[PATCH 0/7] drm/i915/display: Enable CONFIG_PREEMPT_RT

[Maarten Lankhorst <dev@lankhorst.se>]

There is a critical section between intel_pipe_update_start() and
intel_pipe_update_end() where we only program hardware registers,
should not take any lock and complete as fast as possible.

The previous approach used to remove the local_irq_enable/disable()
in this critical, but that increases the probability that the time
sensitive section does not complete in 100 µs, potentially causing
the hardware to hang.

I went through all the lockdep splats that occured in CI, and fixed
them 1 by 1 until there were none left. This additionally improves
latency by not removing any locks in the fastpath.

On Xe the implicit DMC wakelock was added, ideally we can get rid
of it, but for now we can simply use the same _fw variants as are
needed on i915.

I believe this series is enough to make xe RT safe.

Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Maarten Lankhorst (6):
  drm/i915/display: Make get_vblank_counter use intel_de_read_fw()
  drm/i915/display: Use intel_de_write_fw in intel_pipe_fastset
  drm/i915/display: Move vblank put until after critical section
  drm/i915/display: Remove locking from intel_vblank_evade critical
    section
  drm/i915/display: Make icl_dsi_frame_update use _fw too
  drm/i915/display: Enable interrupts earlier on PREEMPT_RT

Mike Galbraith (1):
  drm/i915: Use preempt_disable/enable_rt() where recommended

 drivers/gpu/drm/i915/display/icl_dsi.c        |  4 +-
 drivers/gpu/drm/i915/display/intel_crtc.c     | 10 +++
 drivers/gpu/drm/i915/display/intel_cursor.c   |  8 +-
 drivers/gpu/drm/i915/display/intel_de.h       |  6 ++
 drivers/gpu/drm/i915/display/intel_display.c  | 36 ++++-----
 drivers/gpu/drm/i915/display/intel_vblank.c   | 80 ++++++++++++-------
 drivers/gpu/drm/i915/display/intel_vrr.c      | 16 ++--
 .../drm/xe/compat-i915-headers/intel_uncore.h |  2 +
 8 files changed, 103 insertions(+), 59 deletions(-)

-- 
2.51.0