Re: [PATCH 2/3 v3] drm/i915: catch gtfifo errors on forcewake_put

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Feb 07, 2012 at 04:21:49PM +0100, Ben Widawsky wrote:
> This is similar to a patch I wrote several months ago. It's been updated
> for the new FORCEWAKE_MT, and it also no longer clears the debug
> register as it may be helpful to get that for the error state.  Also
> recommended by Chris Wilson, use WARN() instead of DRM_ERROR, so we can
> get a backtrace.
> 
> v2: Replace POSTING_READ with I915_READ_NOTRACE(GTFIFODBG). Recommended
> by Chris Wilson
> 
> v3: Pull the fifo check out into a helper function to reduce code
> duplication
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_drv.c |   15 +++++++++++++--
>  1 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 1658cfd..a7858a1 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -379,16 +379,27 @@ void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
>  		dev_priv->display.force_wake_get(dev_priv);
>  }
>  
> +static void gen6_gt_check_fifodbg(struct drm_i915_private *dev_priv)
> +{
> +	u32 gtfifodbg;
> +	gtfifodbg = I915_READ_NOTRACE(GTFIFODBG);
> +	WARN(gtfifodbg & GT_FIFO_CPU_ERROR_MASK,
> +	     "MMIO read or write has been dropped %x\n", gtfifodbg);
> +	I915_WRITE_NOTRACE(GTFIFODBG, GT_FIFO_CPU_ERROR_MASK);

I think we should move the write out of line and only do it when we're
actually catching an error.
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48