[Intel-gfx] [PATCH 1/2] drm/i915: Detect page faults during hangcheck

[Daniel Vetter]

On Fri, Dec 05, 2014 at 02:15:21PM +0000, Chris Wilson wrote:
> On Sandybridge+, the GPU provides the ERROR register for detecting page
> faults. Hook this up to our hangcheck so that we can dump the error
> state soon after such an event occurs. This would be better inside an
> interrupt handler, but it serves a purpose here as it detects that our
> initial context setup is invalid...
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_irq.c     | 5 +++++
>  drivers/gpu/drm/i915/intel_uncore.c | 2 ++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 7913a72ce30a..eb2149b941e4 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -2969,6 +2969,11 @@ static void i915_hangcheck_elapsed(unsigned long data)
>  	if (!i915.enable_hangcheck)
>  		return;
>  
> +	if (INTEL_INFO(dev_priv)->gen >= 6 && I915_READ(ERROR_GEN6)) {
> +		i915_handle_error(dev, false, "GPU reported a page fault");

Is the full hangcheck state actually useful for debugging these
pagefaults? The gpu doesn't seem to fall over completely, so I guess ACTHD
and friends are somewhere in nirvana.

Enabling the interrupts would definitely be useful though. I think all the
handler code is written already (perhaps a few missing drm_debug lines),
it's just that we don't enable these interrupt sources by default.
-Daniel

> +		I915_WRITE(ERROR_GEN6, 0);
> +	}
> +
>  	for_each_ring(ring, dev_priv, i) {
>  		u64 acthd;
>  		u32 seqno;
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 0655b44651a7..67f2e24c5bc5 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -535,6 +535,8 @@ static void __intel_uncore_early_sanitize(struct drm_device *dev,
>  	if (IS_GEN6(dev) || IS_GEN7(dev))
>  		__raw_i915_write32(dev_priv, GTFIFODBG,
>  				   __raw_i915_read32(dev_priv, GTFIFODBG));
> +	if (INTEL_INFO(dev)->gen >= 6)
> +		__raw_i915_write32(dev_priv, ERROR_GEN6, 0);
>  
>  	intel_uncore_forcewake_reset(dev, restore_forcewake);
>  }
> -- 
> 2.1.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch