[Intel-gfx] [PATCH 14/18] drm/i915: Don't enable IPS when pixel rate exceeds 95% of cdclk

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

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

Tested-by: Timo Aaltonen <tjaalton at ubuntu.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83497
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 30 ++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h     |  1 +
 drivers/gpu/drm/i915/intel_pm.c      | 16 +++++++---------
 3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5eeb456..4e0ffc9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5520,12 +5520,38 @@ retry:
 	return setup_ok ? 0 : -EINVAL;
 }
 
+static bool pipe_config_supports_ips(struct drm_i915_private *dev_priv,
+				     struct intel_crtc_config *pipe_config)
+{
+	if (pipe_config->pipe_bpp > 24)
+		return false;
+
+	/* HSW can handle pixel rate up to cdclk? */
+	if (IS_HASWELL(dev_priv->dev))
+		return true;
+
+	/*
+	 * FIXME if we compare against max we should then
+	 * increase the cdclk frequency when the current
+	 * value is too low. The other option is to compare
+	 * against the cdclk frqeuncy we're going have post
+	 * modeset (ie. one we computed using other constraints).
+	 * Need to measure whether using a lower cdclk w/o IPS
+	 * is better or worse than a higher cdclk w/ IPS.
+	 */
+	return ilk_pipe_pixel_rate(pipe_config) <=
+		dev_priv->max_cdclk_freq * 95 / 100;
+}
+
 static void hsw_compute_ips_config(struct intel_crtc *crtc,
 				   struct intel_crtc_config *pipe_config)
 {
+	struct drm_device *dev = crtc->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
 	pipe_config->ips_enabled = i915.enable_ips &&
-				   hsw_crtc_supports_ips(crtc) &&
-				   pipe_config->pipe_bpp <= 24;
+		hsw_crtc_supports_ips(crtc) &&
+		pipe_config_supports_ips(dev_priv, pipe_config);
 }
 
 static int intel_crtc_compute_config(struct intel_crtc *crtc,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3ff59a9..1a7808f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1169,6 +1169,7 @@ void ilk_wm_get_hw_state(struct drm_device *dev);
 void skl_wm_get_hw_state(struct drm_device *dev);
 void skl_ddb_get_hw_state(struct drm_i915_private *dev_priv,
 			  struct skl_ddb_allocation *ddb /* out */);
+uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_config *pipe_config);
 
 
 /* intel_sdvo.c */
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 58fdfb0..d9bfd5e 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1892,23 +1892,21 @@ static void i845_update_wm(struct drm_crtc *unused_crtc)
 	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_config *pipe_config)
 {
-	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	uint32_t pixel_rate;
 
-	pixel_rate = intel_crtc->config.adjusted_mode.crtc_clock;
+	pixel_rate = pipe_config->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)
@@ -2522,7 +2520,7 @@ static void ilk_compute_wm_parameters(struct drm_crtc *crtc,
 
 	p->active = true;
 	p->pipe_htotal = intel_crtc->config.adjusted_mode.crtc_htotal;
-	p->pixel_rate = ilk_pipe_pixel_rate(dev, crtc);
+	p->pixel_rate = ilk_pipe_pixel_rate(&intel_crtc->config);
 	p->pri.bytes_per_pixel = crtc->primary->fb->bits_per_pixel / 8;
 	p->cur.bytes_per_pixel = 4;
 	p->pri.horiz_pixels = intel_crtc->config.pipe_src_w;
-- 
2.0.4