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

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

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;
 }
 
 /*
-- 
2.1.4

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