[Intel-gfx] [PATCH 12/21] drm/i915/slpc: Send shutdown event

[Chris Wilson]

On Wed, Apr 27, 2016 at 06:10:56PM -0700, tom.orourke at intel.com wrote:
> From: Tom O'Rourke <Tom.O'Rourke at intel.com>
> 
> Send SLPC shutdown event during disable, suspend, and reset
> operations.  Sending shutdown event while already shutdown
> is OK.
> 
> v2: return void instead of ignored error code (Paulo)
> 
> Signed-off-by: Tom O'Rourke <Tom.O'Rourke at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_slpc.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_slpc.c b/drivers/gpu/drm/i915/intel_slpc.c
> index 3fd46ac..076d07b 100644
> --- a/drivers/gpu/drm/i915/intel_slpc.c
> +++ b/drivers/gpu/drm/i915/intel_slpc.c
> @@ -56,6 +56,23 @@ static void host2guc_slpc_reset(struct drm_device *dev)
>  	host2guc_slpc(dev_priv, data, 4);
>  }
>  
> +static void host2guc_slpc_shutdown(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_i915_gem_object *obj = dev_priv->guc.slpc.shared_data_obj;
> +	u32 data[4];
> +	u64 shared_data_gtt_offset = i915_gem_obj_ggtt_offset(obj);
> +
> +	data[0] = HOST2GUC_ACTION_SLPC_REQUEST;
> +	data[1] = SLPC_EVENT(SLPC_EVENT_SHUTDOWN, 2);
> +	data[2] = lower_32_bits(shared_data_gtt_offset);
> +	data[3] = upper_32_bits(shared_data_gtt_offset);
> +
> +	WARN_ON(0 != data[3]);

Why WARN here? Why not WARN during setup and clamp the GGTT to what the
GuC supports? Shutting the stable door after the horse has bolted...

What happens to the guc if this WARN fires? Is it even sensible to be
programming the hardware to a value you know is bogus? These are the
questions you raise by having an unhandled WARN.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre