Re: [PATCH 06/18] drm/i915: Delay allocation of stolen space for FBC

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, 19 Oct 2012 18:03:12 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> As we may wish to wrap regions preallocated by the BIOS, we need to do
> that before carving out contiguous chunks of stolen space for FBC.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

More nitckicks:
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

> ---
>  drivers/gpu/drm/i915/i915_drv.h        |    2 +
>  drivers/gpu/drm/i915/i915_gem_stolen.c |  115 ++++++++++++++++----------------
>  drivers/gpu/drm/i915/intel_display.c   |    3 +
>  drivers/gpu/drm/i915/intel_pm.c        |    3 +-
>  4 files changed, 66 insertions(+), 57 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 589b2f3..997abb3 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1516,6 +1516,8 @@ int i915_gem_evict_everything(struct drm_device *dev);
>  
>  /* i915_gem_stolen.c */
>  int i915_gem_init_stolen(struct drm_device *dev);
> +int i915_gem_stolen_setup_compression(struct drm_device *dev);
> +void i915_gem_stolen_cleanup_compression(struct drm_device *dev);
>  void i915_gem_cleanup_stolen(struct drm_device *dev);
>  
>  /* i915_gem_tiling.c */
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index d023ed6..68ef22a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -89,21 +89,13 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
>  	return base;
>  }
>  
> -static void i915_warn_stolen(struct drm_device *dev)
> -{
> -	DRM_INFO("not enough stolen space for compressed buffer, disabling\n");
> -	DRM_INFO("hint: you may be able to increase stolen memory size in the BIOS to avoid this\n");
> -}
> -
> -static void i915_setup_compression(struct drm_device *dev, int size)
> +static int i915_setup_compression(struct drm_device *dev, int size)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_mm_node *compressed_fb, *uninitialized_var(compressed_llb);
> -	unsigned long cfb_base;
> -	unsigned long ll_base = 0;
>  
> -	/* Just in case the BIOS is doing something questionable. */
> -	intel_disable_fbc(dev);
> +	DRM_DEBUG_KMS("reserving %d bytes of contiguous stolen space for FBC\n",
> +		      size);
>  

I see you've moved this to modeset init. I question whether we even need
it at all.


>  	compressed_fb = drm_mm_search_free(&dev_priv->mm.stolen, size, 4096, 0);
>  	if (compressed_fb)
> @@ -111,11 +103,11 @@ static void i915_setup_compression(struct drm_device *dev, int size)
>  	if (!compressed_fb)
>  		goto err;
>  
> -	cfb_base = dev_priv->mm.stolen_base + compressed_fb->start;
> -	if (!cfb_base)
> -		goto err_fb;
> -
> -	if (!(IS_GM45(dev) || HAS_PCH_SPLIT(dev))) {
> +	if (HAS_PCH_SPLIT(dev))
> +		I915_WRITE(ILK_DPFC_CB_BASE, compressed_fb->start);
> +	else if (IS_GM45(dev)) {
> +		I915_WRITE(DPFC_CB_BASE, compressed_fb->start);
> +	} else {
>  		compressed_llb = drm_mm_search_free(&dev_priv->mm.stolen,
>  						    4096, 4096, 0);
>  		if (compressed_llb)
> @@ -124,56 +116,81 @@ static void i915_setup_compression(struct drm_device *dev, int size)
>  		if (!compressed_llb)
>  			goto err_fb;
>  
> -		ll_base = dev_priv->mm.stolen_base + compressed_llb->start;
> -		if (!ll_base)
> -			goto err_llb;
> -	}
> +		dev_priv->compressed_llb = compressed_llb;
>  
> -	dev_priv->cfb_size = size;
> +		I915_WRITE(FBC_CFB_BASE,
> +			   dev_priv->mm.stolen_base + compressed_fb->start);
> +		I915_WRITE(FBC_LL_BASE,
> +			   dev_priv->mm.stolen_base + compressed_llb->start);
> +	}
>  
>  	dev_priv->compressed_fb = compressed_fb;
> -	if (HAS_PCH_SPLIT(dev))
> -		I915_WRITE(ILK_DPFC_CB_BASE, compressed_fb->start);
> -	else if (IS_GM45(dev)) {
> -		I915_WRITE(DPFC_CB_BASE, compressed_fb->start);
> -	} else {
> -		I915_WRITE(FBC_CFB_BASE, cfb_base);
> -		I915_WRITE(FBC_LL_BASE, ll_base);
> -		dev_priv->compressed_llb = compressed_llb;
> -	}
> +	dev_priv->cfb_size = size;
>  
> -	DRM_DEBUG_KMS("FBC base 0x%08lx, ll base 0x%08lx, size %dM\n",
> -		      (long)cfb_base, (long)ll_base, size >> 20);
> -	return;
> +	return size;
>  
> -err_llb:
> -	drm_mm_put_block(compressed_llb);
>  err_fb:
>  	drm_mm_put_block(compressed_fb);
>  err:
>  	dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
> -	i915_warn_stolen(dev);
> +	DRM_INFO("not enough stolen space for compressed buffer (need %d bytes), disabling\n", size);
> +	DRM_INFO("hint: you may be able to increase stolen memory size in the BIOS to avoid this\n");
> +	return 0;
> +}
> +
> +int i915_gem_stolen_setup_compression(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_mm_node *node;
> +	unsigned long hole_start, hole_end, size;
> +
> +	if (dev_priv->mm.stolen_base == 0)
> +		return 0;
> +
> +	if (dev_priv->cfb_size)
> +		return dev_priv->cfb_size;
> +
> +	/* Try to set up FBC with a reasonable compressed buffer size */
> +	size = 0;
> +	drm_mm_for_each_hole(node, &dev_priv->mm.stolen, hole_start, hole_end) {
> +		unsigned long hole_size = hole_end - hole_start;
> +		if (hole_size > size)
> +			size = hole_size;
> +	}
> +
> +	/* Try to get a 32M buffer... */
> +	if (size > (36*1024*1024))
> +		size = 32*1024*1024;
> +	else /* fall back to 3/4 of the stolen space */
> +		size = size * 3 / 4;
> +
> +	return i915_setup_compression(dev, size);
>  }
> 

It seems a bit silly that you traverse the hole list here only to
traverse it again later with drm_mm_search_free. If you know you want
32MB, how about you try for that with search free, and then if that
fails, go for the drm_mm_for_each_hole?

afaict, this slightly differs from the old code in that it doesn't
respect i915_powersave any longer. I have no issue with that, but if
that's truly not an oversight on my part, something in the commit
message might be nice.

You've also changed from 3/4 to 7/8 for no apparent reason. Not great
for bisecting. At least you updated the comment.

 
> -static void i915_cleanup_compression(struct drm_device *dev)
> +void i915_gem_stolen_cleanup_compression(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  
> -	drm_mm_put_block(dev_priv->compressed_fb);
> +	if (dev_priv->cfb_size == 0)
> +		return;
> +
> +	if (dev_priv->compressed_fb)
> +		drm_mm_put_block(dev_priv->compressed_fb);
> +
>  	if (dev_priv->compressed_llb)
>  		drm_mm_put_block(dev_priv->compressed_llb);
> +
> +	dev_priv->cfb_size = 0;
>  }
>  
>  void i915_gem_cleanup_stolen(struct drm_device *dev)
>  {
> -	if (I915_HAS_FBC(dev) && i915_powersave)
> -		i915_cleanup_compression(dev);
> +	i915_gem_stolen_cleanup_compression(dev);
>  }
>  

I think we lost the meaning of i915_powersave again here, but I could
be mistaken.

>  int i915_gem_init_stolen(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> -	unsigned long prealloc_size = dev_priv->mm.gtt->stolen_size;
>  
>  	dev_priv->mm.stolen_base = i915_stolen_to_physical(dev);
>  	if (dev_priv->mm.stolen_base == 0)
> @@ -183,21 +200,7 @@ int i915_gem_init_stolen(struct drm_device *dev)
>  		      dev_priv->mm.gtt->stolen_size, dev_priv->mm.stolen_base);
>  
>  	/* Basic memrange allocator for stolen space */
> -	drm_mm_init(&dev_priv->mm.stolen, 0, prealloc_size);
> -
> -	/* Try to set up FBC with a reasonable compressed buffer size */
> -	if (I915_HAS_FBC(dev) && i915_powersave) {
> -		int cfb_size;
> -
> -		/* Leave 1M for line length buffer & misc. */
> -
> -		/* Try to get a 32M buffer... */
> -		if (prealloc_size > (36*1024*1024))
> -			cfb_size = 32*1024*1024;
> -		else /* fall back to 7/8 of the stolen space */
> -			cfb_size = prealloc_size * 7 / 8;
> -		i915_setup_compression(dev, cfb_size);
> -	}
> +	drm_mm_init(&dev_priv->mm.stolen, 0, dev_priv->mm.gtt->stolen_size);
>  
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index c2c219b..2ef497d0 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -8351,6 +8351,9 @@ void intel_modeset_init(struct drm_device *dev)
>  	/* Just disable it once at startup */
>  	i915_disable_vga(dev);
>  	intel_setup_outputs(dev);
> +
> +	/* Just in case the BIOS is doing something questionable. */
> +	intel_disable_fbc(dev);
>  }
>  
>  static void
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 2b3cddf..9ee53cb 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -440,7 +440,7 @@ void intel_update_fbc(struct drm_device *dev)
>  		dev_priv->no_fbc_reason = FBC_MODULE_PARAM;
>  		goto out_disable;
>  	}
> -	if (intel_fb->obj->base.size > dev_priv->cfb_size) {
> +	if (intel_fb->obj->base.size > i915_gem_stolen_setup_compression(dev)) {
>  		DRM_DEBUG_KMS("framebuffer too large, disabling "
>  			      "compression\n");
>  		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
> @@ -526,6 +526,7 @@ out_disable:
>  		DRM_DEBUG_KMS("unsupported config, disabling FBC\n");
>  		intel_disable_fbc(dev);
>  	}
> +	i915_gem_stolen_cleanup_compression(dev);
>  }
>  
>  static void i915_pineview_get_mem_freq(struct drm_device *dev)



-- 
Ben Widawsky, Intel Open Source Technology Center