Re: [PATCH] drm/i915: Park the GPU on module load

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

On 14/09/2018 09:34, Chris Wilson wrote:
> Once we have flushed the first request through the system to both load a
> context and record the default state; tell the GPU to park and idle
> itself, putting itself immediately (hopefully at least) into a
> powersaving state, and allowing ourselves to start from known state
> after setting up all our bookkeeping.

Otherwise this would happen after a second or so, when the idle work 
handler does it. Crucial thing to mention is I think the park/unpark 
cycle which sets up the pinned default state.

Alternative to patch could be to extract 
__intel_engine_pin_default_state to be called from here and from 
intel_engines_unpark.

But I guess there is some value in going powersave as soon as possible 
so okay.

> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 89834ce19acd..be9d012d851b 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -5414,6 +5414,14 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
>   
>   	assert_kernel_context_is_current(i915);
>   
> +	/*
> +	 * Immediately park the GPU so that we enable powersaving and
> +	 * treat it as idle. The next time we issue a request, we will
> +	 * unpark and start using the engine->pinned_default_state, otherwise
> +	 * it is in limbo and an early reset may fail.
> +	 */
> +	__i915_gem_park(i915);

Why not after we have grabbed the default state?

I was worried this might access a sleeping device but apparently at 
least vma unbind takes the rpm ref. Still, just this I think makes it 
more logical to park after we have grabbed the default state, instead o 
putting the device to sleep and then immediately waking up below.

> +
>   	for_each_engine(engine, i915, id) {
>   		struct i915_vma *state;
>   
> 

Regards,

Tvrtko
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