Re: [PATCH 06/10] drm/i915: Enable vblank_disable_immediate on gen2

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 14, 2015 at 06:23:45PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Since
> commit 4dfd648 ("drm: Use vblank timestamps to guesstimate how many vblanks were missed")
> the vblank code can cook up a frame counter value based on
> the vblank timestamps (as long as they're accurate), so there's
> no longer any need to keep vblank interrupts enabled on gen2
> when no one is interested in them. So let's opt into the
> immediate disable scheme on gen2 as well.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Yeah makes sense. Userspace that cares can simply ask for a vblank event
in 1000 frames or so, to keep the vblank interrupt enabled.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/i915/i915_irq.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 37ec8427359a..111edda1e73d 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -4437,14 +4437,7 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
>  		dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
>  	}
>  
> -	/*
> -	 * Opt out of the vblank disable timer on everything except gen2.
> -	 * Gen2 doesn't have a hardware frame counter and so depends on
> -	 * vblank interrupts to produce sane vblank seuquence numbers.
> -	 */
> -	if (!IS_GEN2(dev_priv))
> -		dev->vblank_disable_immediate = true;
> -
> +	dev->vblank_disable_immediate = true;
>  	dev->driver->get_vblank_timestamp = i915_get_vblank_timestamp;
>  	dev->driver->get_scanout_position = i915_get_crtc_scanoutpos;
>  
> -- 
> 2.4.10
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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