Re: [Intel-gfx] [PATCH] drm/i915: Check for driver readyness before handling an underrun interrupt

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 26 Feb 2015, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> When we takeover from the BIOS and install our interrupt handler, the
> BIOS may have left us a few surprises in the form of spontaneous
> interrupts. (This is especially likely on hardware like 965gm where
> display fifo underruns are continuous and the GMCH cannot filter that
> interrupt souce.) As we enable our IRQ early so that we can use it
> during hardware probing, our interrupt handler must be prepared to
> handle a few sources prior to being fully configured. As such, we need
> to add a simple is-ready check prior to dereferencing our KMS state for
> reporting underruns.
>
> Reported-by: Rob Clark <rclark@redhat.com>
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1193972

"You are not authorized to access bug #1193972. To see this bug, you
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Meh.

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: stable@vger.kernel.org
> ---
>  drivers/gpu/drm/i915/intel_fifo_underrun.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_fifo_underrun.c b/drivers/gpu/drm/i915/intel_fifo_underrun.c
> index 04e248dd2259..f2fd992e3cd8 100644
> --- a/drivers/gpu/drm/i915/intel_fifo_underrun.c
> +++ b/drivers/gpu/drm/i915/intel_fifo_underrun.c
> @@ -282,16 +282,6 @@ bool intel_set_cpu_fifo_underrun_reporting(struct drm_i915_private *dev_priv,
>  	return ret;
>  }
>  
> -static bool
> -__cpu_fifo_underrun_reporting_enabled(struct drm_i915_private *dev_priv,
> -				      enum pipe pipe)
> -{
> -	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> -	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> -
> -	return !intel_crtc->cpu_fifo_underrun_disabled;
> -}
> -
>  /**
>   * intel_set_pch_fifo_underrun_reporting - set PCH fifo underrun reporting state
>   * @dev_priv: i915 device instance
> @@ -352,9 +342,15 @@ bool intel_set_pch_fifo_underrun_reporting(struct drm_i915_private *dev_priv,
>  void intel_cpu_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
>  					 enum pipe pipe)
>  {
> +	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> +
> +	/* We may be called too early in init, thanks BIOS! */
> +	if (crtc == NULL)
> +		return;
> +
>  	/* GMCH can't disable fifo underruns, filter them. */
>  	if (HAS_GMCH_DISPLAY(dev_priv->dev) &&
> -	    !__cpu_fifo_underrun_reporting_enabled(dev_priv, pipe))
> +	    !to_intel_crtc(crtc)->cpu_fifo_underrun_disabled)
>  		return;
>  
>  	if (intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false))
> -- 
> 2.1.4
>
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-- 
Jani Nikula, Intel Open Source Technology Center