Re: [PATCH 1/3] drm/i915: Suppress spurious CPU FIFO underruns on ILK-IVB

Chris Wilson
2015-11-21T10:51:53Z

On Fri, Nov 20, 2015 at 10:09:18PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We still get spurious pipe underruns on ILK/SNB/IVB under two
> circumstances when dealing with PCH ports:
> * When the pipe has been disabled, but FDI RX/TX is still enabled
> * During FDI link training
>
> Both cases seem to happen at least when we do VGA+HDMI cloning
> from the same pipe. I don't think I've seen them when not cloning,
> but can't be 100% sure.
>
> Disable underrun reporting around those places to eliminate the
> dmesg errors.
>
> Testcase: igt/kms_setmode/basic-clone-single-crtc
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>

I wondered if logging the suppressed errors would be of any use? Does
the check_cpu_fifo work if the reporting is disabled? Could we do a
manual check and DRM_DEBUG_KMS() if the enable did generate a failure.
If the check_cpu_fifo does work, won't we still get the error from the
added check in atomic_commit()?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre