[Intel-gfx] [PATCH v8 3/7] drm/i915: Check plane configuration properly

[Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>]

From: Stanislav Lisovskiy <stanislav.lisovskiY@intel.com>

Checking with hweight8 if plane configuration had
changed seems to be wrong as different plane configs
can result in a same hamming weight.
So lets check the bitmask itself.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index e93a553a344d..a9ab66d97360 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -14614,7 +14614,13 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
 		old_active_planes = old_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
 		new_active_planes = new_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
 
-		if (hweight8(old_active_planes) == hweight8(new_active_planes))
+		/*
+		 * Not only the number of planes, but if the plane configuration had
+		 * changed might already mean we need to recompute min CDCLK,
+		 * because different planes might consume different amount of Dbuf bandwidth
+		 * according to formula: Bw per plane = Pixel rate * bpp * pipe/plane scale factor
+		 */
+		if (old_active_planes == new_active_planes)
 			continue;
 
 		ret = intel_crtc_add_planes_to_state(state, crtc, new_active_planes);
-- 
2.24.1.485.gad05a3d8e5

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