[Intel-gfx] [PATCH 1/2] drm/i915: Try to allocate more memory for FBC on Ironlake or GM45

[Eric Anholt]

On Tue, 23 Mar 2010 11:12:32 +0800, Zhenyu Wang <zhenyuw at linux.intel.com> wrote:
> From: Zhao Yakui <yakui.zhao at intel.com>
> 
> The framebuffer compression can support up to 2K lines and 4K pixels, which
> means that it can support up to 32M memory space. But now it is only limited
> to 8M.
> 
> Try to allocate more memory for FBC from the stolen memory on Ironlake or
> GM45.
> 
> Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
> Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_dma.c      |   16 +++++++++++++---
>  drivers/gpu/drm/i915/intel_display.c |   10 ++++++++--
>  2 files changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 902d286..61fb967 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1451,9 +1451,19 @@ static int i915_load_modeset_init(struct drm_device *dev,
>  		int cfb_size;
>  
>  		/* Try to get an 8M buffer... */
> -		if (prealloc_size > (9*1024*1024))
> -			cfb_size = 8*1024*1024;
> -		else /* fall back to 7/8 of the stolen space */
> +		if (prealloc_size > (9*1024*1024)) {
> +			if (IS_GM45(dev) || IS_IRONLAKE_M(dev)) {
> +				if (prealloc_size >= (64 * 1024 * 1024))
> +					cfb_size = 32 * 1024 * 1024;
> +				else if (prealloc_size >= (32 * 1024 * 1024))
> +					cfb_size = 24 * 1024 * 1024;
> +				else if (prealloc_size >= (16 * 1024 * 1024))
> +					cfb_size = 12 * 1024 * 1024;
> +				else
> +					cfb_size = 8 * 1024 * 1024;
> +			} else
> +				cfb_size = 8*1024*1024;
> +		} else /* fall back to 7/8 of the stolen space */
>  			cfb_size = prealloc_size * 7 / 8;
>  		i915_setup_compression(dev, cfb_size);

The previous code was "use 7/8 of stolen space, unless we've got a ton
in which case limit it to 8MB."  Now your code has a ton of cases to use
4/8MB increments.  Why 4/8MB increments?  From the commit message, I
would have expected:

cfb_size = prealloc_size * 7 / 8;
if (IS_GM45(dev) || IS_IRONLAKE_M(dev)) {
   if (cfb_size > (32 * 1024 * 1024))
      cfb_size = 32 * 1024 * 1024;
} else {
   if (cfb_size > (8 * 1024 * 1024))
      cfb_size = 8 * 1024 * 1024;
}
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