From: Tarun Vyas Date: Wed, 27 Jun 2018 13:02:50 -0700 Subject: drm/i915: Wait for PSR exit before checking for vblank evasion Git-commit: a608987970b929e250957e4e3fb891f1f10eff6f Patch-mainline: v4.19-rc1 References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166 The PIPEDSL freezes on PSR entry and if PSR hasn't fully exited, then the pipe_update_start call schedules itself out to check back later. On ChromeOS-4.4 kernel, which is fairly up-to-date w.r.t drm/i915 but lags w.r.t core kernel code, hot plugging an external display triggers tons of "potential atomic update errors" in the dmesg, on *pipe A*. A closer analysis reveals that we try to read the scanline 3 times and eventually timeout, b/c PSR hasn't exited fully leading to a PIPEDSL stuck @ 1599. This issue is not seen on upstream kernels, b/c for *some* reason we loop inside intel_pipe_update start for ~2+ msec which in this case is more than enough to exit PSR fully, hence an *unstuck* PIPEDSL counter, hence no error. On the other hand, the ChromeOS kernel spends ~1.1 msec looping inside intel_pipe_update_start and hence errors out b/c the source is still in PSR. Regardless, we should wait for PSR exit (if PSR is disabled, we incur a ~1-2 usec penalty) before reading the PIPEDSL, b/c if we haven't fully exited PSR, then checking for vblank evasion isn't actually applicable. v4: Comment explaining psr_wait after enabling VBL interrupts (DK) v5: CAN_PSR() to handle platforms that don't support PSR. v6: Handle local_irq_disable on early return (Chris) Acked-by: Daniel Vetter Reviewed-by: Dhinakaran Pandiyan Signed-off-by: Tarun Vyas Signed-off-by: Dhinakaran Pandiyan Link: https://patchwork.freedesktop.org/patch/msgid/20180627200250.1515-2-tarun.vyas@intel.com Acked-by: Petr Tesarik --- drivers/gpu/drm/i915/intel_sprite.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) --- a/drivers/gpu/drm/i915/intel_sprite.c +++ b/drivers/gpu/drm/i915/intel_sprite.c @@ -107,13 +107,21 @@ void intel_pipe_update_start(const struc VBLANK_EVASION_TIME_US); max = vblank_start - 1; - local_irq_disable(); - if (min <= 0 || max <= 0) - return; + goto irq_disable; if (WARN_ON(drm_crtc_vblank_get(&crtc->base))) - return; + goto irq_disable; + + /* + * Wait for psr to idle out after enabling the VBL interrupts + * VBL interrupts will start the PSR exit and prevent a PSR + * re-entry as well. + */ + if (CAN_PSR(dev_priv) && intel_psr_wait_for_idle(dev_priv)) + DRM_ERROR("PSR idle timed out, atomic update may fail\n"); + + local_irq_disable(); crtc->debug.min_vbl = min; crtc->debug.max_vbl = max; @@ -171,6 +179,10 @@ void intel_pipe_update_start(const struc crtc->debug.start_vbl_count = intel_crtc_get_vblank_counter(crtc); trace_i915_pipe_update_vblank_evaded(crtc); + return; + +irq_disable: + local_irq_disable(); } /**