Re: [PATCH] drm/i915: Add BXT Sprite plane fractional scalings

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Nov 18, 2015 at 05:13:01PM +0530, Nabendu Maiti wrote:
> On older platforms scalers/cliping used to provide destination size an
> exact multiple of src size.
> Gen-9 and above support fractional ratio of dst/src so that source is
> not manipulated to meet the exact multiple factor.
> 
> Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sprite.c | 48 +++++++++++++++++++++----------------
>  1 file changed, 28 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> index 2b96f33..e8c17ae 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -813,29 +813,37 @@ intel_check_sprite_plane(struct drm_plane *plane,
>  	crtc_h = drm_rect_height(dst);
>  
>  	if (state->visible) {
> -		/* check again in case clipping clamped the results */
> -		hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
> -		if (hscale < 0) {
> -			DRM_DEBUG_KMS("Horizontal scaling factor out of limits\n");
> -			drm_rect_debug_print("src: ", src, true);
> -			drm_rect_debug_print("dst: ", dst, false);
> -
> -			return hscale;
> -		}
>  
> -		vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
> -		if (vscale < 0) {
> -			DRM_DEBUG_KMS("Vertical scaling factor out of limits\n");
> -			drm_rect_debug_print("src: ", src, true);
> -			drm_rect_debug_print("dst: ", dst, false);
> +		/* Gen 9 and above has fractional scaling support */
> +		if (INTEL_INFO(plane->dev)->gen < 9) {
>  
> -			return vscale;
> -		}
> +			/* check again in case clipping clamped the results */
> +			hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
> +			if (hscale < 0) {
> +				DRM_DEBUG_KMS("Horizontal scaling factor out of limits\n");
> +				drm_rect_debug_print("src: ", src, true);
> +				drm_rect_debug_print("dst: ", dst, false);
> +
> +				return hscale;
> +			}
> +
> +			vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
> +			if (vscale < 0) {
> +				DRM_DEBUG_KMS("Vertical scaling factor out of limits\n");
> +				drm_rect_debug_print("src: ", src, true);
> +				drm_rect_debug_print("dst: ", dst, false);
>  
> -		/* Make the source viewport size an exact multiple of the scaling factors. */
> -		drm_rect_adjust_size(src,
> -				     drm_rect_width(dst) * hscale - drm_rect_width(src),
> -				     drm_rect_height(dst) * vscale - drm_rect_height(src));
> +				return vscale;
> +			}
> +
> +			/*
> +			 * Make the source viewport size an exact
> +			 * multiple of the scaling factors.
> +			 */
> +			drm_rect_adjust_size(src,
> +					     drm_rect_width(dst) * hscale - drm_rect_width(src),
> +					     drm_rect_height(dst) * vscale - drm_rect_height(src));
> +		}

NAK. This code just makes sure the actual scaling ratio matches what we
calculated. As in there may have been some amount of rounding involved
etc.

The part you actually want to change is what comes after this where we
throw away the fractional part of the coordinates. And then you need to
change the actual hw programming so that we actually feed the sub-pixel
coordinates to the hardware.

>  
>  		drm_rect_rotate_inv(src, fb->width << 16, fb->height << 16,
>  				    state->base.rotation);
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC
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