[Intel-gfx] [PATCH v4 1/8] drm/i915/skl+: use linetime latency instead of ddb size

[Paulo Zanoni]

Em Qui, 2016-10-13 às 16:28 +0530, Kumar, Mahesh escreveu:
> This patch make changes to use linetime latency instead of allocated
> DDB size during plane watermark calculation in switch case, This is
> required to implement new DDB allocation algorithm.
> 
> In New Algorithm DDB is allocated based on WM values, because of
> which
> number of DDB blocks will not be available during WM calculation,
> So this "linetime latency" is suggested by SV/HW team to use during
> switch-case for WM blocks selection.
> 
> Changes since v1:
>  - Rebase on top of Paulo's patch series
> Changes since v2:
>  - Fix if-else condition (pointed by Maarten)
> 
> Signed-off-by: "Kumar, Mahesh" <mahesh1.kumar at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> index 7f1748a..098336d 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3616,10 +3616,14 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
>  		selected_result = max(method2, y_tile_minimum);
>  	} else {
> +		uint32_t linetime_us = 0;
> +
> +		linetime_us = DIV_ROUND_UP(width * 1000,
> +				skl_pipe_pixel_rate(cstate));

Can't we just call skl_compute_linetime_wm() here? I don't like having
two pieces of the code computing the same thing. My last round of bug
fixes included a fix for duplicated code that got out of sync after
spec changes.

>  		if ((cpp * cstate->base.adjusted_mode.crtc_htotal /
> 512 < 1) &&
>  		    (plane_bytes_per_line / 512 < 1))
>  			selected_result = method2;
> -		else if ((ddb_allocation / plane_blocks_per_line) >=
> 1)
> +		else if (latency >= linetime_us)

Still doesn't match the spec. The "ddb_allocation /
planes_block_per_line" is still necessary.

>  			selected_result = min(method1, method2);
>  		else
>  			selected_result = method1;