drm/i915/skl+: consider max supported plane pixel rate while scaling

A display resolution is only supported if it meets all the restrictions
below for Maximum Pipe Pixel Rate.

The display resolution must fit within the maximum pixel rate output
from the pipe. Make sure that the display pipe is able to feed pixels at
a rate required to support the desired resolution.
For each enabled plane on the pipe {
    If plane scaling enabled {
	Horizontal down scale amount = Maximum[1, plane horizontal size /
		    scaler horizontal window size]
	Vertical down scale amount = Maximum[1, plane vertical size /
		    scaler vertical window size]
	Plane down scale amount = Horizontal down scale amount *
		    Vertical down scale amount
	Plane Ratio = 1 / Plane down scale amount
    }
    Else {
	Plane Ratio = 1
    }
    If plane source pixel format is 64 bits per pixel {
	Plane Ratio = Plane Ratio * 8/9
    }
}

Pipe Ratio = Minimum Plane Ratio of all enabled planes on the pipe

If pipe scaling is enabled {
    Horizontal down scale amount = Maximum[1, pipe horizontal source size /
		scaler horizontal window size]
    Vertical down scale amount = Maximum[1, pipe vertical source size /
		scaler vertical window size]
    Note: The progressive fetch - interlace display mode is equivalent to a
		2.0 vertical down scale
    Pipe down scale amount = Horizontal down scale amount *
		Vertical down scale amount
    Pipe Ratio = Pipe Ratio / Pipe down scale amount
}

Pipe maximum pixel rate = CDCLK frequency * Pipe Ratio

In this patch our calculation is based on pipe downscale amount
(plane max downscale amount * pipe downscale amount) instead of Pipe
Ratio. So,
max supported crtc clock with given scaling = CDCLK / pipe downscale.
Flip will fail if,
current crtc clock > max supported crct clock with given scaling.

Changes since V1:
 - separate out fixed_16_16 wrapper API definition
Changes since V2:
 - Fix buggy crtc !active condition (Maarten)
 - use intel_wm_plane_visible wrapper as per Maarten's suggestion
Changes since V3:
 - Change failure return from ERANGE to EINVAL
Changes since V4:
 - Rebase based on previous patch changes
Changes since V5:
 - return EINVAL instead of continue (Maarten)
Changes since V6:
 - Improve commit message
 - Address review comment
Changes since V7:
 - use !enable instead of !active
 - rename config variable for consistency (Maarten)

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170526151546.25025-4-mahesh1.kumar@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -11186,6 +11186,9 @@ static int intel_crtc_atomic_check(struct drm_crtc *crtc,
 		if (mode_changed)
 			ret = skl_update_scaler_crtc(pipe_config);
 
+		if (!ret)
+			ret = skl_check_pipe_max_pixel_rate(intel_crtc,
+							    pipe_config);
 		if (!ret)
 			ret = intel_atomic_setup_scalers(dev_priv, intel_crtc,
 							 pipe_config);

drivers/gpu/drm/i915/intel_drv.h

@@ -1886,6 +1886,8 @@ bool skl_ddb_allocation_overlaps(const struct skl_ddb_entry **entries,
 				 int ignore);
 bool ilk_disable_lp_wm(struct drm_device *dev);
 int sanitize_rc6_option(struct drm_i915_private *dev_priv, int enable_rc6);
+int skl_check_pipe_max_pixel_rate(struct intel_crtc *intel_crtc,
+				  struct intel_crtc_state *cstate);
 static inline int intel_enable_rc6(void)
 {
 	return i915.enable_rc6;

drivers/gpu/drm/i915/intel_pm.c

@@ -3863,6 +3863,93 @@ skl_plane_downscale_amount(const struct intel_crtc_state *cstate,
 	return mul_fixed16(downscale_w, downscale_h);
 }
 
+static uint_fixed_16_16_t
+skl_pipe_downscale_amount(const struct intel_crtc_state *crtc_state)
+{
+	uint_fixed_16_16_t pipe_downscale = u32_to_fixed_16_16(1);
+
+	if (!crtc_state->base.enable)
+		return pipe_downscale;
+
+	if (crtc_state->pch_pfit.enabled) {
+		uint32_t src_w, src_h, dst_w, dst_h;
+		uint32_t pfit_size = crtc_state->pch_pfit.size;
+		uint_fixed_16_16_t fp_w_ratio, fp_h_ratio;
+		uint_fixed_16_16_t downscale_h, downscale_w;
+
+		src_w = crtc_state->pipe_src_w;
+		src_h = crtc_state->pipe_src_h;
+		dst_w = pfit_size >> 16;
+		dst_h = pfit_size & 0xffff;
+
+		if (!dst_w || !dst_h)
+			return pipe_downscale;
+
+		fp_w_ratio = fixed_16_16_div(src_w, dst_w);
+		fp_h_ratio = fixed_16_16_div(src_h, dst_h);
+		downscale_w = max_fixed_16_16(fp_w_ratio, u32_to_fixed_16_16(1));
+		downscale_h = max_fixed_16_16(fp_h_ratio, u32_to_fixed_16_16(1));
+
+		pipe_downscale = mul_fixed16(downscale_w, downscale_h);
+	}
+
+	return pipe_downscale;
+}
+
+int skl_check_pipe_max_pixel_rate(struct intel_crtc *intel_crtc,
+				  struct intel_crtc_state *cstate)
+{
+	struct drm_crtc_state *crtc_state = &cstate->base;
+	struct drm_atomic_state *state = crtc_state->state;
+	struct drm_plane *plane;
+	const struct drm_plane_state *pstate;
+	struct intel_plane_state *intel_pstate;
+	int crtc_clock, cdclk;
+	uint32_t pipe_max_pixel_rate;
+	uint_fixed_16_16_t pipe_downscale;
+	uint_fixed_16_16_t max_downscale = u32_to_fixed_16_16(1);
+
+	if (!cstate->base.enable)
+		return 0;
+
+	drm_atomic_crtc_state_for_each_plane_state(plane, pstate, crtc_state) {
+		uint_fixed_16_16_t plane_downscale;
+		uint_fixed_16_16_t fp_9_div_8 = fixed_16_16_div(9, 8);
+		int bpp;
+
+		if (!intel_wm_plane_visible(cstate,
+					    to_intel_plane_state(pstate)))
+			continue;
+
+		if (WARN_ON(!pstate->fb))
+			return -EINVAL;
+
+		intel_pstate = to_intel_plane_state(pstate);
+		plane_downscale = skl_plane_downscale_amount(cstate,
+							     intel_pstate);
+		bpp = pstate->fb->format->cpp[0] * 8;
+		if (bpp == 64)
+			plane_downscale = mul_fixed16(plane_downscale,
+						      fp_9_div_8);
+
+		max_downscale = max_fixed_16_16(plane_downscale, max_downscale);
+	}
+	pipe_downscale = skl_pipe_downscale_amount(cstate);
+
+	pipe_downscale = mul_fixed16(pipe_downscale, max_downscale);
+
+	crtc_clock = crtc_state->adjusted_mode.crtc_clock;
+	cdclk = to_intel_atomic_state(state)->cdclk.logical.cdclk;
+	pipe_max_pixel_rate = div_round_up_u32_fixed16(cdclk, pipe_downscale);
+
+	if (pipe_max_pixel_rate < crtc_clock) {
+		DRM_ERROR("Max supported pixel clock with scaling exceeded\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static unsigned int
 skl_plane_relative_data_rate(const struct intel_crtc_state *cstate,
 			     const struct drm_plane_state *pstate,