Re: [PATCH 2/4] drm/i915/skl+: calculate ddb minimum allocation (v6)

[Mahesh Kumar <mahesh1.kumar@intel.com>]

Reviewed-by: Kumar Mahesh <mahesh1.kumar@intel.com>

On Tuesday 31 May 2016 10:28 PM, Matt Roper 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.
>
> v3 (by Matt):
>   - Fix boolean logic for !fb test in skl_ddb_min_alloc()
>   - Adjust negative tiling format comparisons in skl_ddb_min_alloc() to
>     improve readability.
>
> v4 (by Matt):
>   - Rebase onto recent atomic watermark changes
>   - Slight tweaks to code flow to make the logic more closely match the
>     description in the bspec.
>
> v5 (by Matt):
>   - Handle minimum scanline calculation properly for 4 & 8 bpp formats.
>     8bpp isn't actually possible right now, but it's listed in the bspec
>     so I've included it here for forward compatibility (similar to how
>     we have logic for NV12).
>
> v6 (by Matt):
>   - Calculate plane_bpp correctly for non-NV12 formats. (Mahesh)
>
> Cc: matthew.d.roper@intel.com
> Signed-off-by: Kumar, Mahesh <mahesh1.kumar@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>   drivers/gpu/drm/i915/intel_pm.c | 70 ++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 65 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 3cf36dc..4e0a952 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3042,6 +3042,69 @@ skl_get_total_relative_data_rate(struct intel_crtc_state *intel_cstate)
>   	return total_data_rate;
>   }
>   
> +static uint16_t
> +skl_ddb_min_alloc(const struct drm_plane_state *pstate,
> +		  const int y)
> +{
> +	struct drm_framebuffer *fb = pstate->fb;
> +	struct intel_plane_state *intel_pstate = to_intel_plane_state(pstate);
> +	uint32_t src_w, src_h;
> +	uint32_t min_scanlines = 8;
> +	uint8_t plane_bpp;
> +
> +	if (WARN_ON(!fb))
> +		return 0;
> +
> +	/* For packed formats, no y-plane, return 0 */
> +	if (y && fb->pixel_format != DRM_FORMAT_NV12)
> +		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;
> +
> +	src_w = drm_rect_width(&intel_pstate->src) >> 16;
> +	src_h = drm_rect_height(&intel_pstate->src) >> 16;
> +
> +	if (intel_rotation_90_or_270(pstate->rotation))
> +		swap(src_w, src_h);
> +
> +	/* Halve UV plane width and height for NV12 */
> +	if (fb->pixel_format == DRM_FORMAT_NV12 && !y) {
> +		src_w /= 2;
> +		src_h /= 2;
> +	}
> +
> +	if (fb->pixel_format == DRM_FORMAT_NV12 && !y)
> +		plane_bpp = drm_format_plane_cpp(fb->pixel_format, 1);
> +	else
> +		plane_bpp = drm_format_plane_cpp(fb->pixel_format, 0);
> +
> +	if (intel_rotation_90_or_270(pstate->rotation)) {
> +		switch (plane_bpp) {
> +		case 1:
> +			min_scanlines = 32;
> +			break;
> +		case 2:
> +			min_scanlines = 16;
> +			break;
> +		case 4:
> +			min_scanlines = 8;
> +			break;
> +		case 8:
> +			min_scanlines = 4;
> +			break;
> +		default:
> +			WARN(1, "Unsupported pixel depth %u for rotation",
> +			     plane_bpp);
> +			min_scanlines = 32;
> +		}
> +	}
> +
> +	return DIV_ROUND_UP((4 * src_w * plane_bpp), 512) * min_scanlines/4 + 3;
> +}
> +
>   static int
>   skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>   		      struct skl_ddb_allocation *ddb /* out */)
> @@ -3104,11 +3167,8 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
>   			continue;
>   		}
>   
> -		minimum[id] = 8;
> -		if (pstate->fb->pixel_format == DRM_FORMAT_NV12)
> -			y_minimum[id] = 8;
> -		else
> -			y_minimum[id] = 0;
> +		minimum[id] = skl_ddb_min_alloc(pstate, 0);
> +		y_minimum[id] = skl_ddb_min_alloc(pstate, 1);
>   	}
>   
>   	for (i = 0; i < PLANE_CURSOR; i++) {

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