Re: [v2 2/6] drm/i915/skl+: calculate ddb minimum allocation

[Matt Roper <matthew.d.roper@intel.com>]

On Wed, Jan 27, 2016 at 09:39:59PM +0530, Shobhit Kumar wrote:
> From: "Kumar, Mahesh" <mahesh1.kumar@intel.com>
> 
> don't always use 8 ddb as minimum, instead calculate using proper
> algorithm.
> 
> v2: optimizations as per Matt's comments.
> 
> Cc: matthew.d.roper@intel.com
> Signed-off-by: Kumar, Mahesh <mahesh1.kumar@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 50 ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 47 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index d55e5d0..708f329 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2928,6 +2928,51 @@ skl_get_total_relative_data_rate(const struct intel_crtc_state *cstate)
>  	return total_data_rate;
>  }
>  
> +static uint16_t
> +skl_ddb_min_alloc(const struct intel_crtc *crtc,
> +		const struct drm_plane *plane, int y)
> +{
> +	struct drm_framebuffer *fb = plane->state->fb;
> +	struct intel_plane_state *pstate = to_intel_plane_state(plane->state);
> +	uint32_t src_w, src_h;
> +	uint32_t min_scanlines = 8;
> +	uint8_t bytes_per_pixel;
> +
> +	/* For packed formats, no y-plane, return 0 */
> +	if (y && !fb && !(fb->pixel_format == DRM_FORMAT_NV12))

I think you meant

        if (!fb || (y && fb->pixel_format != DRM_FORMAT_NV12))

right?

> +		return 0;
> +
> +	/* For Non Y-tile return 8-blocks */
> +	if (!(fb->modifier[0] == I915_FORMAT_MOD_Y_TILED) &&
> +	    !(fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED))
> +		return 8;

Minor nitpick, but it might be more readable to use != instead of
pulling the ! outside of the comparison.  On my first quick read I
missed the inversions.


Matt

> +
> +	src_w = drm_rect_width(&pstate->src) >> 16;
> +	src_h = drm_rect_height(&pstate->src) >> 16;
> +
> +	if (intel_rotation_90_or_270(plane->state->rotation))
> +		swap(src_w, src_h);
> +
> +	bytes_per_pixel = y ? drm_format_plane_cpp(fb->pixel_format, 0) :
> +		drm_format_plane_cpp(fb->pixel_format, 1);
> +
> +	if (intel_rotation_90_or_270(plane->state->rotation)) {
> +		switch (bytes_per_pixel) {
> +		case 1:
> +			min_scanlines = 32;
> +			break;
> +		case 2:
> +			min_scanlines = 16;
> +			break;
> +		case 8:
> +			WARN(1, "Unsupported pixel depth for rotation");
> +		}
> +	}
> +
> +	return DIV_ROUND_UP((4 * src_w / (y ? 1 : 2) * bytes_per_pixel), 512) *
> +							min_scanlines/4 + 3;
> +}
> +
>  static void
>  skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>  		      struct skl_ddb_allocation *ddb /* out */)
> @@ -2964,7 +3009,6 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>  	/* 1. Allocate the mininum required blocks for each active plane */
>  	for_each_intel_plane_on_crtc(dev, intel_crtc, intel_plane) {
>  		struct drm_plane *plane = &intel_plane->base;
> -		struct drm_framebuffer *fb = plane->state->fb;
>  		int id = skl_wm_plane_id(intel_plane);
>  
>  		if (!to_intel_plane_state(plane->state)->visible)
> @@ -2973,9 +3017,9 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>  		if (plane->type == DRM_PLANE_TYPE_CURSOR)
>  			continue;
>  
> -		minimum[id] = 8;
> +		minimum[id] = skl_ddb_min_alloc(intel_crtc, plane, 0);
>  		alloc_size -= minimum[id];
> -		y_minimum[id] = (fb->pixel_format == DRM_FORMAT_NV12) ? 8 : 0;
> +		y_minimum[id] = skl_ddb_min_alloc(intel_crtc, plane, 1);
>  		alloc_size -= y_minimum[id];
>  	}
>  
> -- 
> 2.5.0
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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