On Thu, 2018-06-21 at 18:03 -0700, Tarun Vyas wrote: > 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. > > Signed-off-by: Tarun Vyas <tarun.vyas@xxxxxxxxx> > --- > drivers/gpu/drm/i915/intel_sprite.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_sprite.c > b/drivers/gpu/drm/i915/intel_sprite.c > index 344c0e709b19..34754771d7a7 100644 > --- a/drivers/gpu/drm/i915/intel_sprite.c > +++ b/drivers/gpu/drm/i915/intel_sprite.c > @@ -107,14 +107,16 @@ void intel_pipe_update_start(const struct > intel_crtc_state *new_crtc_state) > VBLANK_EVASION > _TIME_US); > max = vblank_start - 1; > > - local_irq_disable(); > - > if (min <= 0 || max <= 0) > return; > > if (WARN_ON(drm_crtc_vblank_get(&crtc->base))) > return; > > + psr_wait_for_idle_lockless(dev_priv); Document the implicit requirement that we enable vblank interrupts before waiting for PSR idle. Looks good to me, I'll wait for others to chime in. The hope is https://bugs.freedesktop.org/show_bug.cgi?id=106678 gets fixed with this patch. > + > + local_irq_disable(); > + > crtc->debug.min_vbl = min; > crtc->debug.max_vbl = max; > trace_i915_pipe_update_start(crtc); _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
