Re: [PATCH 09/10] drm/i915: flush system agent TLBs on SNB

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 22 Oct 2012 18:34:14 -0700
Ben Widawsky <ben@bwidawsk.net> wrote:

> This allows us to map the PTEs WC. I've not done thorough testing or
> performance measurements with this patch, but it should be decent.
> 
> This is based on a patch from Jesse with the original commit message
> > I've only lightly tested this so far, but the corruption seems to be
> > gone if I write the GFX_FLSH_CNTL reg after binding an object.  This
> > register should control the TLB for the system agent, which is what CPU
> > mapped objects will go through.
> 
> It has been updated for the new AGP-less code by me, and included with
> it is feedback from the original patch.
> 
> CC: Jesse Barnes <jbarnes@virtuousgeek.org>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 5 +++--
>  drivers/gpu/drm/i915/i915_reg.h     | 2 ++
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 16fe960..e5f0a7f 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -391,6 +391,7 @@ static void gen6_ggtt_bind_object(struct drm_i915_gem_object *obj,
>  	}
>  
>  out:
> +	I915_WRITE(GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
>  	/* XXX: This serves as a posting read preserving the way the old code
>  	 * works. It's not clear if this is strictly necessary or just voodoo
>  	 * based on what I've tried to gather from the docs.
> @@ -593,8 +594,8 @@ int i915_gem_gtt_init(struct drm_device *dev)
>  	if (ret)
>  		return ret;
>  
> -	dev_priv->mm.gtt->gtt = ioremap(gtt_bus_addr,
> -					dev_priv->mm.gtt->gtt_total_entries * sizeof(gtt_pte_t));
> +	dev_priv->mm.gtt->gtt = ioremap_wc(gtt_bus_addr,
> +					   dev_priv->mm.gtt->gtt_total_entries * sizeof(gtt_pte_t));
>  
>  	/* GMADR is the PCI aperture used by SW to access tiled GFX surfaces in a linear fashion. */
>  	DRM_DEBUG_DRIVER("GMADR size = %dM\n", dev_priv->mm.gtt->gtt_mappable_entries >> 8);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 1d54328..e8c578f 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -683,6 +683,8 @@
>  #define   CM0_RC_OP_FLUSH_DISABLE (1<<0)
>  #define BB_ADDR		0x02140 /* 8 bytes */
>  #define GFX_FLSH_CNTL	0x02170 /* 915+ only */
> +#define GFX_FLSH_CNTL_GEN6	0x101008
> +#define   GFX_FLSH_CNTL_EN	(1<<0)
>  #define ECOSKPD		0x021d0
>  #define   ECO_GATING_CX_ONLY	(1<<3)
>  #define   ECO_FLIP_DONE		(1<<0)

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

-- 
Jesse Barnes, Intel Open Source Technology Center