drm/i915: Don't enable IPS when pixel rate exceeds 95%

Bspec says we shouldn't enable IPS on BDW when the pipe pixel rate
exceeds 95% of the core display clock. Apparently this can cause
underruns.

There's no similar restriction listed for HSW, so leave that one alone
for now.

v2: Add pipe_config_supports_ips() (Chris)
v3: Compare against the max cdclk insted of the current cdclk
v4: Rebased to the latest
v5: Rebased to the latest
v6: Fix for patch style problems

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83497
Tested-by: Timo Aaltonen <tjaalton@ubuntu.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 5db429e..d091fec 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1434,23 +1434,22 @@
 	I915_WRITE(FW_BLC, fwater_lo);
 }
 
-static uint32_t ilk_pipe_pixel_rate(struct drm_device *dev,
-				    struct drm_crtc *crtc)
+uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_state *pipe_config)
 {
-	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	uint32_t pixel_rate;
 
-	pixel_rate = intel_crtc->config->base.adjusted_mode.crtc_clock;
+	pixel_rate = pipe_config->base.adjusted_mode.crtc_clock;
 
 	/* We only use IF-ID interlacing. If we ever use PF-ID we'll need to
 	 * adjust the pixel_rate here. */
 
-	if (intel_crtc->config->pch_pfit.enabled) {
+	if (pipe_config->pch_pfit.enabled) {
 		uint64_t pipe_w, pipe_h, pfit_w, pfit_h;
-		uint32_t pfit_size = intel_crtc->config->pch_pfit.size;
+		uint32_t pfit_size = pipe_config->pch_pfit.size;
 
-		pipe_w = intel_crtc->config->pipe_src_w;
-		pipe_h = intel_crtc->config->pipe_src_h;
+		pipe_w = pipe_config->pipe_src_w;
+		pipe_h = pipe_config->pipe_src_h;
+
 		pfit_w = (pfit_size >> 16) & 0xFFFF;
 		pfit_h = pfit_size & 0xFFFF;
 		if (pipe_w < pfit_w)
@@ -2066,7 +2065,7 @@
 
 	p->active = true;
 	p->pipe_htotal = intel_crtc->config->base.adjusted_mode.crtc_htotal;
-	p->pixel_rate = ilk_pipe_pixel_rate(dev, crtc);
+	p->pixel_rate = ilk_pipe_pixel_rate(intel_crtc->config);
 
 	if (crtc->primary->state->fb)
 		p->pri.bytes_per_pixel =