[Intel-gfx] [PATCH v2] drm/i915: Use intel_plane_data_rate for min_cdclk calculation

[Stanislav Lisovskiy]

There seems to be a bit of confusing redundancy in a way, how
plane data rate/min cdclk are calculated.
In fact both min cdclk, pixel rate and plane data rate are all
part of the same formula as per BSpec.

However currently we have intel_plane_data_rate, which is used
to calculate plane data rate and which is also used in bandwidth
calculations. However for calculating min_cdclk we have another
piece of code, doing almost same calculation, but a bit differently
and in a different place. However as both are actually part of same
formula, probably would be wise to use plane data rate calculations
as a basis anyway, thus avoiding code duplication and possible bugs
related to this.

Another thing is that I've noticed that during min_cdclk calculations
we account for plane scaling, while for plane data rate, we don't.
crtc->pixel_rate seems to account only for pipe ratio, however it is
clearly stated in BSpec that plane data rate also need to account
plane ratio as well.

So what this commit does is:
- Adds a plane ratio calculation to intel_plane_data_rate
- Removes redundant calculations from skl_plane_min_cdclk which is
  used for gen9+ and now uses intel_plane_data_rate as a basis from
  there as well.

v2: - Don't use 64 division if not needed(Ville Syrjälä)
    - Now use intel_plane_pixel_rate as a basis for calculations both
      at intel_plane_data_rate and skl_plane_min_cdclk(Ville Syrjälä)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
---
 .../gpu/drm/i915/display/intel_atomic_plane.c | 22 +++++++++++++++-
 .../gpu/drm/i915/display/intel_atomic_plane.h |  3 +++
 drivers/gpu/drm/i915/display/intel_sprite.c   | 26 +++++++------------
 3 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
index c86d7a35c816..3bd7ea9bf1b4 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
@@ -133,11 +133,31 @@ intel_plane_destroy_state(struct drm_plane *plane,
 	kfree(plane_state);
 }
 
+unsigned int intel_plane_pixel_rate(const struct intel_crtc_state *crtc_state,
+				    const struct intel_plane_state *plane_state)
+{
+	unsigned int src_w, src_h, dst_w, dst_h;
+
+	src_w = drm_rect_width(&plane_state->uapi.src) >> 16;
+	src_h = drm_rect_height(&plane_state->uapi.src) >> 16;
+	dst_w = drm_rect_width(&plane_state->uapi.dst);
+	dst_h = drm_rect_height(&plane_state->uapi.dst);
+
+	/* Downscaling limits the maximum pixel rate */
+	dst_w = min(src_w, dst_w);
+	dst_h = min(src_h, dst_h);
+
+	return DIV_ROUND_UP(mul_u32_u32(crtc_state->pixel_rate,
+			    src_w * src_h),
+			    mul_u32_u32(dst_w, dst_h));
+}
+
 unsigned int intel_plane_data_rate(const struct intel_crtc_state *crtc_state,
 				   const struct intel_plane_state *plane_state)
 {
 	const struct drm_framebuffer *fb = plane_state->hw.fb;
 	unsigned int cpp;
+	unsigned int plane_pixel_rate = intel_plane_pixel_rate(crtc_state, plane_state);
 
 	if (!plane_state->uapi.visible)
 		return 0;
@@ -153,7 +173,7 @@ unsigned int intel_plane_data_rate(const struct intel_crtc_state *crtc_state,
 	if (fb->format->is_yuv && fb->format->num_planes > 1)
 		cpp *= 4;
 
-	return cpp * crtc_state->pixel_rate;
+	return mul_u32_u32(plane_pixel_rate, cpp);
 }
 
 int intel_plane_calc_min_cdclk(struct intel_atomic_state *state,
diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.h b/drivers/gpu/drm/i915/display/intel_atomic_plane.h
index 2bcf15e34728..a6bbf42bae1f 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.h
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.h
@@ -18,6 +18,9 @@ struct intel_plane_state;
 
 extern const struct drm_plane_helper_funcs intel_plane_helper_funcs;
 
+unsigned int intel_plane_pixel_rate(const struct intel_crtc_state *crtc_state,
+				    const struct intel_plane_state *plane_state);
+
 unsigned int intel_plane_data_rate(const struct intel_crtc_state *crtc_state,
 				   const struct intel_plane_state *plane_state);
 void intel_plane_copy_uapi_to_hw_state(struct intel_plane_state *plane_state,
diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c b/drivers/gpu/drm/i915/display/intel_sprite.c
index 7abeefe8dce5..4fa3081e2074 100644
--- a/drivers/gpu/drm/i915/display/intel_sprite.c
+++ b/drivers/gpu/drm/i915/display/intel_sprite.c
@@ -330,9 +330,9 @@ bool icl_is_hdr_plane(struct drm_i915_private *dev_priv, enum plane_id plane_id)
 }
 
 static void
-skl_plane_ratio(const struct intel_crtc_state *crtc_state,
-		const struct intel_plane_state *plane_state,
-		unsigned int *num, unsigned int *den)
+skl_plane_bpp_constraints(const struct intel_crtc_state *crtc_state,
+			  const struct intel_plane_state *plane_state,
+			  unsigned int *num, unsigned int *den)
 {
 	struct drm_i915_private *dev_priv = to_i915(plane_state->uapi.plane->dev);
 	const struct drm_framebuffer *fb = plane_state->hw.fb;
@@ -355,27 +355,19 @@ static int skl_plane_min_cdclk(const struct intel_crtc_state *crtc_state,
 			       const struct intel_plane_state *plane_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(plane_state->uapi.plane->dev);
-	unsigned int pixel_rate = crtc_state->pixel_rate;
-	unsigned int src_w, src_h, dst_w, dst_h;
 	unsigned int num, den;
+	int plane_pixel_rate = intel_plane_pixel_rate(crtc_state, plane_state);
 
-	skl_plane_ratio(crtc_state, plane_state, &num, &den);
+	skl_plane_bpp_constraints(crtc_state, plane_state, &num, &den);
 
 	/* two pixels per clock on glk+ */
 	if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
 		den *= 2;
 
-	src_w = drm_rect_width(&plane_state->uapi.src) >> 16;
-	src_h = drm_rect_height(&plane_state->uapi.src) >> 16;
-	dst_w = drm_rect_width(&plane_state->uapi.dst);
-	dst_h = drm_rect_height(&plane_state->uapi.dst);
-
-	/* Downscaling limits the maximum pixel rate */
-	dst_w = min(src_w, dst_w);
-	dst_h = min(src_h, dst_h);
-
-	return DIV64_U64_ROUND_UP(mul_u32_u32(pixel_rate * num, src_w * src_h),
-				  mul_u32_u32(den, dst_w * dst_h));
+	/*
+	 * Plane pixel rate is a pipe pixel rate * plane ratio * pipe ratio
+	 */
+	return DIV64_U64_ROUND_UP(plane_pixel_rate * num, den);
 }
 
 static unsigned int
-- 
2.24.1.485.gad05a3d8e5