From: Tarun <tarun.v...@intel.com>
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 supported and active
on the current pipe) before reading the PIPEDSL, b/c if we haven't
fully exited PSR, then checking for vblank evasion isn't actually
applicable.
This scenario applies to a configuration with an additional pipe,
as of now.
---
drivers/gpu/drm/i915/intel_sprite.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_sprite.c
b/drivers/gpu/drm/i915/intel_sprite.c
index aa1dfaa692b9..135b41568503 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -107,14 +107,17 @@ 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;
+ if(new_crtc_state->has_psr && dev_priv->psr.active)
+ intel_wait_for_register(dev_priv, EDP_PSR_STATUS,
EDP_PSR_STATUS_STATE_MASK, EDP_PSR_STATUS_STATE_IDLE, 5);
+
+ local_irq_disable();
+
crtc->debug.min_vbl = min;
crtc->debug.max_vbl = max;
trace_i915_pipe_update_start(crtc);
--
2.13.5
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