Re: [PATCH] drm/i915: Check engine->default_state mapping on module load

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 14/09/2018 10:21, Chris Wilson wrote:
> Check we can indeed acquire a WB mapping of the context image on module
> load. Later this will give us the opportunity to validate that we can
> switch from WC to WB as required.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index be9d012d851b..37353afec66e 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -5424,6 +5424,7 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
>   
>   	for_each_engine(engine, i915, id) {
>   		struct i915_vma *state;
> +		void *vaddr;
>   
>   		state = to_intel_context(ctx, engine)->state;
>   		if (!state)
> @@ -5446,6 +5447,16 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
>   			goto err_active;
>   
>   		engine->default_state = i915_gem_object_get(state->obj);
> +
> +		/* Check we can acquire the image of the context state */
> +		vaddr = i915_gem_object_pin_map(engine->default_state,
> +						I915_MAP_WB);
> +		if (IS_ERR(vaddr)) {
> +			err = PTR_ERR(vaddr);
> +			goto err_active;
> +		}
> +
> +		i915_gem_object_unpin_map(engine->default_state);

Ah this perhaps strengthens the argument to have 
__intel_engines_pin_default_state? (And the unpin pair.)

And I guess you made this patch come before the switch to WC since it is 
not FORCE_WB here?

Regards,

Tvrtko

>   	}
>   
>   	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)) {
> 
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