Quoting Dhinakaran Pandiyan (2018-02-16 04:33:22)
> With fbdev, screen freezes after a few continuous PSR exit->enter cycles.
> Printing out the PSR status register clearly showed this freeze coincided
> with exiting when the hardware is in a transitory state. So wait for a max
> of 100 ms (~6 frames) for PSR to become active and then exit.
>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_psr.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index 2a31c7cbdb41..d6669f5f890f 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -738,6 +738,17 @@ static void intel_psr_exit(struct drm_i915_private *dev_priv)
> WARN_ON(!(val & EDP_PSR2_ENABLE));
> I915_WRITE(EDP_PSR2_CTL, val & ~EDP_PSR2_ENABLE);
> } else {
> + /* Wait for about 6 frames in case we just enabled PSR,
> + * this prevents the screen from freezing as the HW does
> + * not seem to be able to back off cleanly it is already
> + * trying to enter PSR.
> + */
> + intel_wait_for_register(dev_priv,
> + EDP_PSR_STATUS,
> + EDP_PSR_STATUS_STATE_MASK,
> + EDP_PSR_STATUS_STATE_SRDENT,
> + 100);
I'm going to suggest that you want a DRM_DEBUG_KMS() (_DRIVER? Not sure
what works best for PSR/frontbuffer-tracking) at least for spotting
trouble when it times out. I would start with a DRM_ERROR for a few CI
passes just to see what's happening on our machines before toning it
down for production.
-Chris
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