From: Mike Galbraith umgwanakikbuti@gmail.com
Commit 8d7849db3eab7 ("drm/i915: Make sprite updates atomic")
started disabling interrupts across atomic updates. This breaks on PREEMPT_RT because within this section the code attempt to acquire spinlock_t locks which are sleeping locks on PREEMPT_RT.
According to the comment the interrupts are disabled to avoid random delays and not required for protection or synchronisation. If this needs to happen with disabled interrupts on PREEMPT_RT, and the whole section is restricted to register access then all sleeping locks need to be acquired before interrupts are disabled and some function maybe moved after enabling interrupts again. This includes: - prepare_to_wait() + finish_wait() due its wake queue. - drm_crtc_vblank_put() -> vblank_disable_fn() drm_device::vbl_lock. - skl_pfit_enable(), intel_update_plane(), vlv_atomic_update_fifo() and maybe others due to intel_uncore::lock - drm_crtc_arm_vblank_event() due to drm_device::event_lock and drm_device::vblank_time_lock.
Don't disable interrupts on PREEMPT_RT during atomic updates.
[bigeasy: drop local locks, commit message]
Signed-off-by: Mike Galbraith umgwanakikbuti@gmail.com Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- drivers/gpu/drm/i915/display/intel_crtc.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c index 254e67141a776..7a39029b083f4 100644 --- a/drivers/gpu/drm/i915/display/intel_crtc.c +++ b/drivers/gpu/drm/i915/display/intel_crtc.c @@ -425,7 +425,8 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) */ intel_psr_wait_for_idle(new_crtc_state);
- local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable();
crtc->debug.min_vbl = min; crtc->debug.max_vbl = max; @@ -450,11 +451,13 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) break; }
- local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable();
timeout = schedule_timeout(timeout);
- local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); }
finish_wait(wq, &wait); @@ -487,7 +490,8 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) return;
irq_disable: - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); }
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_VBLANK_EVADE) @@ -566,7 +570,8 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state) new_crtc_state->uapi.event = NULL; }
- local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable();
/* Send VRR Push to terminate Vblank */ intel_vrr_send_push(new_crtc_state);