Re: [PATCH 1/2] drm/i915/bdw: Add WT caching ability

From: Ben Widawsky <ben@bwidawsk.net>
To: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Intel GFX <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 1/2] drm/i915/bdw: Add WT caching ability
Date: Sat, 29 Mar 2014 15:58:11 -0700	[thread overview]
Message-ID: <20140329225810.GA15455@bwidawsk.net> (raw)
In-Reply-To: <1396133802-15385-1-git-send-email-benjamin.widawsky@intel.com>

On Sat, Mar 29, 2014 at 03:56:41PM -0700, Ben Widawsky wrote:
> I don't have any insight on what parts can do what. The docs do seem to
> suggest WT caching works in at least the same manner as it doesn't on
> Haswell.
> 

That's a freudian slip... s/doesn't/does/

> The addr = 0  is to shut up GCC:
> drivers/gpu/drm/i915/i915_gem_gtt.c:80:7: warning: 'addr' may be used
> uninitialized in this function [-Wmaybe-uninitialized]
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_drv.h     | 11 ++++++-----
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 17 +++++++++++++----
>  2 files changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index e23bb73..896fe8e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1822,11 +1822,12 @@ struct drm_i915_cmd_table {
>  #define BSD_RING		(1<<VCS)
>  #define BLT_RING		(1<<BCS)
>  #define VEBOX_RING		(1<<VECS)
> -#define HAS_BSD(dev)            (INTEL_INFO(dev)->ring_mask & BSD_RING)
> -#define HAS_BLT(dev)            (INTEL_INFO(dev)->ring_mask & BLT_RING)
> -#define HAS_VEBOX(dev)            (INTEL_INFO(dev)->ring_mask & VEBOX_RING)
> -#define HAS_LLC(dev)            (INTEL_INFO(dev)->has_llc)
> -#define HAS_WT(dev)            (IS_HASWELL(dev) && to_i915(dev)->ellc_size)
> +#define HAS_BSD(dev)		(INTEL_INFO(dev)->ring_mask & BSD_RING)
> +#define HAS_BLT(dev)		(INTEL_INFO(dev)->ring_mask & BLT_RING)
> +#define HAS_VEBOX(dev)		(INTEL_INFO(dev)->ring_mask & VEBOX_RING)
> +#define HAS_LLC(dev)		(INTEL_INFO(dev)->has_llc)
> +#define HAS_WT(dev)		((IS_HASWELL(dev) || IS_BROADWELL(dev)) && \
> +				 to_i915(dev)->ellc_size)
>  #define I915_NEED_GFX_HWS(dev)	(INTEL_INFO(dev)->need_gfx_hws)
>  
>  #define HAS_HW_CONTEXTS(dev)	(INTEL_INFO(dev)->gen >= 6)
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 4467974..10d00ee 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -68,10 +68,19 @@ static inline gen8_gtt_pte_t gen8_pte_encode(dma_addr_t addr,
>  {
>  	gen8_gtt_pte_t pte = valid ? _PAGE_PRESENT | _PAGE_RW : 0;
>  	pte |= addr;
> -	if (level != I915_CACHE_NONE)
> -		pte |= PPAT_CACHED_INDEX;
> -	else
> +
> +	switch (level) {
> +	case I915_CACHE_NONE:
>  		pte |= PPAT_UNCACHED_INDEX;
> +		break;
> +	case I915_CACHE_WT:
> +		pte |= PPAT_DISPLAY_ELLC_INDEX;
> +		break;
> +	default:
> +		pte |= PPAT_CACHED_INDEX;
> +		break;
> +	}
> +
>  	return pte;
>  }
>  
> @@ -1367,7 +1376,7 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
>  		(gen8_gtt_pte_t __iomem *)dev_priv->gtt.gsm + first_entry;
>  	int i = 0;
>  	struct sg_page_iter sg_iter;
> -	dma_addr_t addr;
> +	dma_addr_t addr = 0;
>  
>  	for_each_sg_page(st->sgl, &sg_iter, st->nents, 0) {
>  		addr = sg_dma_address(sg_iter.sg) +
> -- 
> 1.9.1
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ben Widawsky, Intel Open Source Technology Center