drm/i915: Check plane configuration properly

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.

v2: Fixed "from" field which got corrupted for some weird reason

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200520145827.15887-1-stanislav.lisovskiy@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index e2f9ec8..1954304 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -14688,7 +14688,13 @@ 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);