Re: [Intel-gfx] [PATCH] drm/i915: Disable AsyncFlip performance optimisations

[Imre Deak <imre.deak@intel.com>]

On Sun, 2013-01-20 at 16:11 +0000, Chris Wilson wrote:
> This is a required workarounds for all products, especially on gen6+
> where it causes the command streamer to fail to parse instructions
> following a WAIT_FOR_EVENT. We use WAIT_FOR_EVENT for synchronising
> between the GPU and the display engines, and so this bit being unset may
> cause hangs.
> 
> References: https://bugzilla.kernel.org/show_bug.cgi?id=52311
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: stable@vger.kernel.org

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/i915_reg.h         |    1 +
>  drivers/gpu/drm/i915/intel_ringbuffer.c |   19 +++++++++++++------
>  2 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 8b81052..db1c034 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -536,6 +536,7 @@
>  #define MI_MODE		0x0209c
>  # define VS_TIMER_DISPATCH				(1 << 6)
>  # define MI_FLUSH_ENABLE				(1 << 12)
> +# define ASYNC_FLIP_PERF_DISABLE			(1 << 14)
>  
>  #define GEN6_GT_MODE	0x20d0
>  #define   GEN6_GT_MODE_HI				(1 << 9)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index ef68037..af7adb0 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -503,13 +503,20 @@ static int init_render_ring(struct intel_ring_buffer *ring)
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	int ret = init_ring_common(ring);
>  
> -	if (INTEL_INFO(dev)->gen > 3) {
> +	if (INTEL_INFO(dev)->gen > 3)
>  		I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(VS_TIMER_DISPATCH));
> -		if (IS_GEN7(dev))
> -			I915_WRITE(GFX_MODE_GEN7,
> -				   _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
> -				   _MASKED_BIT_ENABLE(GFX_REPLAY_MODE));
> -	}
> +
> +	/* We need to disable the AsyncFlip performance optimisations in order
> +	 * to use MI_WAIT_FOR_EVENT within the CS. It should already be
> +	 * programmed to '1' on all products.
> +	 */
> +	if (INTEL_INFO(dev)->gen >= 6)
> +		I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(ASYNC_FLIP_PERF_DISABLE));
> +
> +	if (IS_GEN7(dev))
> +		I915_WRITE(GFX_MODE_GEN7,
> +			   _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
> +			   _MASKED_BIT_ENABLE(GFX_REPLAY_MODE));
>  
>  	if (INTEL_INFO(dev)->gen >= 5) {
>  		ret = init_pipe_control(ring);