Re: [PATCH 1/2] drm/i915/bdw: Use scratch page table for GEN8 PPGTT

[Ben Widawsky <ben@bwidawsk.net>]

On Sat, Mar 08, 2014 at 11:58:16AM -0800, Ben Widawsky wrote:
> I'm not clear if the hardware is still subject to the same prefetching
> issues that made us use a scratch page in the first place. In either
> case, we're using garbage with the current code (we will end up using
> offset 0).
> 
> This may be the cause of our current gem_cpu_reloc regression with
> PPGTT. I cannot test it at the moment.
> 

Wait NVM... that wasn't gen8. I can't associate this one with a bug.

> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 5427d6d..0f39090 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -1169,7 +1169,6 @@ static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>  	ppgtt->base.clear_range = gen6_ppgtt_clear_range;
>  	ppgtt->base.insert_entries = gen6_ppgtt_insert_entries;
>  	ppgtt->base.cleanup = gen6_ppgtt_cleanup;
> -	ppgtt->base.scratch = dev_priv->gtt.base.scratch;
>  	ppgtt->base.start = 0;
>  	ppgtt->base.total = GEN6_PPGTT_PD_ENTRIES * I915_PPGTT_PT_ENTRIES * PAGE_SIZE;
>  	ppgtt->debug_dump = gen6_dump_ppgtt;
> @@ -1192,6 +1191,7 @@ int i915_gem_init_ppgtt(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt)
>  	int ret = 0;
>  
>  	ppgtt->base.dev = dev;
> +	ppgtt->base.scratch = dev_priv->gtt.base.scratch;
>  
>  	if (INTEL_INFO(dev)->gen < 8)
>  		ret = gen6_ppgtt_init(ppgtt);
> -- 
> 1.9.0
> 

-- 
Ben Widawsky, Intel Open Source Technology Center