Re: [PATCH 2/2] drm/i915: i8xx also doesn't like multiple oustanding pageflips

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Wed,  4 Aug 2010 21:22:10 +0200
Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> My i855GM suffers from a 80k/s interrupt storm without this.
> So add 2nd gen to the list of things that don't like more than
> one outstanding pageflip request.
> 
> Furthermore I've changed the busy loop into a ringbuffer wait.
> Busy-loops that don't check whether the chip died are simply evil.
> And performance should actually improve, because there's usually
> a decent amount of rendering queued on the gpu, hopefully rendering
> that MI_WAIT into a noop by the time it's executed.
> 
> The current code holds dev->struct_mutex while executing this loop,
> hence stalling all other gem activity anyway.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: stabel@kernel.org
> ---
>  drivers/gpu/drm/i915/intel_display.c |   13 ++++++++-----
>  1 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 8135ee0..7b6035e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4916,14 +4916,17 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  	work->pending_flip_obj = obj;
>  
>  	if (intel_crtc->plane)
> -		flip_mask = I915_DISPLAY_PLANE_B_FLIP_PENDING_INTERRUPT;
> +		flip_mask = MI_WAIT_FOR_PLANE_B_FLIP;
>  	else
> -		flip_mask = I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT;
> +		flip_mask = MI_WAIT_FOR_PLANE_A_FLIP;
>  
>  	/* Wait for any previous flip to finish */
> -	if (IS_GEN3(dev))
> -		while (I915_READ(ISR) & flip_mask)
> -			;
> +	if (IS_GEN3(dev) || IS_GEN2(dev)) {
> +		BEGIN_LP_RING(2);
> +		OUT_RING(MI_WAIT_FOR_EVENT | flip_mask);
> +		OUT_RING(0);
> +		ADVANCE_LP_RING();
> +	}
>  
>  	BEGIN_LP_RING(4);
>  	if (IS_I965G(dev)) {

This looks nicer than what was there before.  Hope it still works on
9xx...

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center