Re: [PATCH 10/22] drm/i915: Support for extra alignment for tiled surfaces

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Oct 14, 2015 at 07:29:02PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> SKL+ needs >4K alignment for tiled surfaces, so make
> intel_compute_page_offset() handle it.
> 
> The way we do it is first we compute the closest tile boundary
> as before, and then figure out how many tiles we need to go
> to reach the desired alignment. The difference in the offset
> is then added into the x/y offsets.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 51 ++++++++++++++++++++++++++++++++----
>  1 file changed, 46 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 5f3abce..85e1473 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2479,6 +2479,39 @@ static void intel_rotate_tile_dims(unsigned int *tile_width,
>  }
>  
>  /*
> + * Adjust the page offset by moving the difference into
> + * the x/y offsets.
> + *
> + * Input tile dimensions and pitch must already be
> + * rotated to match x and y, and in pixel units.
> + * intel_rotate_tile_dims() gives exactly that.
> + */
> +static void intel_adjust_page_offset(int *x, int *y,
> +				     unsigned int tile_width,
> +				     unsigned int tile_height,
> +				     unsigned int tile_size,
> +				     unsigned int pitch,
> +				     unsigned int old_offset,
> +				     unsigned int new_offset)
> +{
> +	unsigned int tiles;
> +
> +	WARN_ON(old_offset & (tile_size - 1));
> +	WARN_ON(new_offset & (tile_size - 1));
> +	WARN_ON(new_offset > old_offset);
> +
> +	tiles = (old_offset - new_offset) / tile_size;
> +	if (tiles == 0)
> +		return;
> +
> +	/* pitch in tiles */
> +	pitch /= tile_width;

Isn't tile_width here now in pixels and no longer in bytes? And we need
bytes here I think, i.e. tile_pitch.

> +
> +	*y += tiles / pitch * tile_height;
> +	*x += tiles % pitch * tile_width;

But here we need tile_width in pixels. I'm confused.

> +}
> +
> +/*
>   * Computes the linear offset to the base tile and adjusts
>   * x, y. bytes per pixel is assumed to be a power-of-two.
>   *
> @@ -2493,6 +2526,12 @@ unsigned long intel_compute_page_offset(struct drm_i915_private *dev_priv,
>  					unsigned int pitch,
>  					unsigned int rotation)
>  {
> +	unsigned int offset, alignment;
> +
> +	alignment = intel_surf_alignment(dev_priv, fb_modifier);
> +	if (alignment)
> +		alignment--;
> +
>  	if (fb_modifier != DRM_FORMAT_MOD_NONE) {
>  		unsigned int tile_size, tile_width, tile_height;
>  		unsigned int tile_rows, tiles;
> @@ -2510,16 +2549,18 @@ unsigned long intel_compute_page_offset(struct drm_i915_private *dev_priv,
>  		tiles = *x / tile_width;
>  		*x %= tile_width;
>  
> -		return (tile_rows * (pitch / tile_width) + tiles) * tile_size;
> -	} else {
> -		unsigned int alignment = intel_linear_alignment(dev_priv) - 1;
> -		unsigned int offset;
> +		offset = (tile_rows * (pitch / tile_width) + tiles) * tile_size;
>  
> +		intel_adjust_page_offset(x, y, tile_width, tile_height,
> +					 tile_size, pitch,
> +					 offset, offset & ~alignment);

offset_aligned = ALIGN(offset, alignment); instead of open-coding it.
-Daniel

> +	} else {
>  		offset = *y * pitch + *x * cpp;
>  		*y = (offset & alignment) / pitch;
>  		*x = ((offset & alignment) - *y * pitch) / cpp;
> -		return offset & ~alignment;
>  	}
> +
> +	return offset & ~alignment;
>  }
>  
>  static int i9xx_format_to_fourcc(int format)
> -- 
> 2.4.9
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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