[PATCH v2 0/9] drm/i915: PREEMPT_RT related fixups.

[Sebastian Andrzej Siewior]

the following patches are from the PREEMPT_RT queue. It is mostly about
disabling interrupts/preemption which leads to problems. Patches 1-4 are
independent of PREEMPT_RT.

Unfortunately DRM_I915_LOW_LEVEL_TRACEPOINTS had to be disabled because
it acquires locks from within trace points. It has been pointed out in
the previous post that this makes any kind of debugging impossible.
Making the uncore.lock a raw_spinlock_t doubles the latencies in my
limited testing [0]. I don't know the difference on other hardware. Also
it worries me a little that wait_for_atomic() has 50ms as the upper
spin/wait limit if the condition does not become true.

I tested it on a SandyBridge with built-in i915 by using X, OpenGL and
playing videos without noticing any warnings. However, some code paths
were not entered.

[0] https://lore.kernel.org/all/20211006164628.s2mtsdd2jdbfyf7g@linutronix.de/

Sebastian