Re: [PATCH 4/4] drm/i915/skl+: Use scaling amount for plane data rate calculation (v4)

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

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

On Friday 20 May 2016 03:33 AM, Matt Roper wrote:
> From: "Kumar, Mahesh" <mahesh1.kumar@intel.com>
>
> if downscaling is enabled plane data rate increases according to scaling
> amount. take scaling amount under consideration while calculating plane
> data rate
>
> v2: Address Matt's comments, where data rate was overridden because of
> missing else.
>
> v3 (by Matt):
>   - Add braces to 'else' branch to match kernel coding style
>   - Adjust final calculation now that skl_plane_downscale_amount()
>     returns 16.16 fixed point value instead of a decimal fixed point
>
> v4 (by Matt):
>   - Avoid integer overflow by making sure final multiplication is
>     treated as 64-bit.
>
> 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 | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 5bd885b..7a486e4 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2993,6 +2993,7 @@ skl_plane_relative_data_rate(const struct intel_crtc_state *cstate,
>   {
>   	struct intel_plane_state *intel_pstate = to_intel_plane_state(pstate);
>   	struct drm_framebuffer *fb = pstate->fb;
> +	uint32_t down_scale_amount, data_rate;
>   	uint32_t width = 0, height = 0;
>   	unsigned format = fb ? fb->pixel_format : DRM_FORMAT_XRGB8888;
>   
> @@ -3012,15 +3013,19 @@ skl_plane_relative_data_rate(const struct intel_crtc_state *cstate,
>   	/* for planar format */
>   	if (format == DRM_FORMAT_NV12) {
>   		if (y)  /* y-plane data rate */
> -			return width * height *
> +			data_rate = width * height *
>   				drm_format_plane_cpp(format, 0);
>   		else    /* uv-plane data rate */
> -			return (width / 2) * (height / 2) *
> +			data_rate = (width / 2) * (height / 2) *
>   				drm_format_plane_cpp(format, 1);
> +	} else {
> +		/* for packed formats */
> +		data_rate = width * height * drm_format_plane_cpp(format, 0);
>   	}
>   
> -	/* for packed formats */
> -	return width * height * drm_format_plane_cpp(format, 0);
> +	down_scale_amount = skl_plane_downscale_amount(intel_pstate);
> +
> +	return (uint64_t)data_rate * down_scale_amount >> 16;
>   }
>   
>   /*

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