[Intel-gfx] [PATCH 1/3] drm/i915: implement IPS feature

[Paulo Zanoni]

From: Paulo Zanoni <paulo.r.zanoni at intel.com>

Intermediate Pixel Storage is a feature that should reduce the number
of times the display engine wakes up memory to read pixels, so it
should allow deeper PC states. IPS can only be enabled on ULT port A
with 8:8:8 pipe pixel formats.

With eDP 1920x1080 and correct watermarks but without FBC this moves
my PC7 residency from 2.5% to around 38%.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |   11 +++++
 drivers/gpu/drm/i915/intel_display.c |   80 +++++++++++++++++++++++++++++++++-
 2 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 32eb97c..65339a7 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -977,6 +977,8 @@
 /* Framebuffer compression for Ivybridge */
 #define IVB_FBC_RT_BASE			0x7020
 
+#define IPS_CTL		0x43408
+#define   IPS_ENABLE	(1 << 31)
 
 #define _HSW_PIPE_SLICE_CHICKEN_1_A	0x420B0
 #define _HSW_PIPE_SLICE_CHICKEN_1_B	0x420B4
@@ -3621,6 +3623,15 @@
 #define _LGC_PALETTE_B           0x4a800
 #define LGC_PALETTE(pipe) _PIPE(pipe, _LGC_PALETTE_A, _LGC_PALETTE_B)
 
+#define _GAMMA_MODE_A		0x4a480
+#define _GAMMA_MODE_B		0x4ac80
+#define GAMMA_MODE(pipe) _PIPE(pipe, _GAMMA_MODE_A, _GAMMA_MODE_B)
+#define GAMMA_MODE_MODE_MASK	(3 << 0)
+#define GAMMA_MODE_MODE_8bit	(0 << 0)
+#define GAMMA_MODE_MODE_10bit	(1 << 0)
+#define GAMMA_MODE_MODE_12bit	(2 << 0)
+#define GAMMA_MODE_MODE_SPLIT	(3 << 0)
+
 /* interrupts */
 #define DE_MASTER_IRQ_CONTROL   (1 << 31)
 #define DE_SPRITEB_FLIP_DONE    (1 << 29)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 48166fe..61e4671 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3340,6 +3340,62 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 	intel_wait_for_vblank(dev, intel_crtc->pipe);
 }
 
+static bool hsw_crtc_supports_ips(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	struct intel_encoder *encoder;
+	bool is_port_a_edp = false;
+
+	if (!IS_ULT(dev))
+		return false;
+
+	for_each_encoder_on_crtc(dev, crtc, encoder)
+		if (encoder->type == INTEL_OUTPUT_EDP)
+			if (enc_to_dig_port(&encoder->base)->port == PORT_A)
+				is_port_a_edp = true;
+	if (!is_port_a_edp)
+		return false;
+
+	if (intel_crtc->config.pipe_bpp != 24)
+		return false;
+
+	return true;
+}
+
+static void hsw_enable_ips(struct drm_crtc *crtc)
+{
+	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
+
+	if (!hsw_crtc_supports_ips(crtc))
+		return;
+
+	DRM_DEBUG_KMS("Enabling IPS\n");
+
+	/* We can only enable IPS after we enable a plane and wait for a vblank.
+	 * We guarantee that the plane is enabled by calling intel_enable_ips
+	 * only after intel_enable_plane. And intel_enable_plane already waits
+	 * for a vblank, so all we need to do here is to enable the IPS bit. */
+	I915_WRITE(IPS_CTL, IPS_ENABLE);
+}
+
+static void hsw_disable_ips(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+
+	if (!hsw_crtc_supports_ips(crtc))
+		return;
+
+	DRM_DEBUG_KMS("Disabling IPS\n");
+
+	I915_WRITE(IPS_CTL, 0);
+
+	/* We need to wait for a vblank before we can disable the plane. */
+	intel_wait_for_vblank(dev, intel_crtc->pipe);
+}
+
 static void haswell_crtc_enable(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
@@ -3387,6 +3443,8 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
 			  intel_crtc->config.has_pch_encoder);
 	intel_enable_plane(dev_priv, plane, pipe);
 
+	hsw_enable_ips(crtc);
+
 	if (intel_crtc->config.has_pch_encoder)
 		lpt_pch_enable(crtc);
 
@@ -3516,6 +3574,8 @@ static void haswell_crtc_disable(struct drm_crtc *crtc)
 	if (dev_priv->cfb_plane == plane)
 		intel_disable_fbc(dev);
 
+	hsw_disable_ips(crtc);
+
 	intel_disable_plane(dev_priv, plane, pipe);
 
 	if (intel_crtc->config.has_pch_encoder)
@@ -6291,8 +6351,10 @@ void intel_crtc_load_lut(struct drm_crtc *crtc)
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	int palreg = PALETTE(intel_crtc->pipe);
+	enum pipe pipe = intel_crtc->pipe;
+	int palreg = PALETTE(pipe);
 	int i;
+	bool reenable_ips = false;
 
 	/* The clocks have to be on to load the palette. */
 	if (!crtc->enabled || !intel_crtc->active)
@@ -6300,7 +6362,18 @@ void intel_crtc_load_lut(struct drm_crtc *crtc)
 
 	/* use legacy palette for Ironlake */
 	if (HAS_PCH_SPLIT(dev))
-		palreg = LGC_PALETTE(intel_crtc->pipe);
+		palreg = LGC_PALETTE(pipe);
+
+	/* Workaround : Do not read or write the pipe palette/gamma data while
+	 * GAMMA_MODE is configured for split gamma and IPS_CTL has IPS enabled.
+	 */
+	if (hsw_crtc_supports_ips(crtc) &&
+	    (I915_READ(IPS_CTL) & IPS_ENABLE) &&
+	    ((I915_READ(GAMMA_MODE(pipe)) & GAMMA_MODE_MODE_MASK) ==
+	     GAMMA_MODE_MODE_SPLIT)) {
+		hsw_disable_ips(crtc);
+		reenable_ips = true;
+	}
 
 	for (i = 0; i < 256; i++) {
 		I915_WRITE(palreg + 4 * i,
@@ -6308,6 +6381,9 @@ void intel_crtc_load_lut(struct drm_crtc *crtc)
 			   (intel_crtc->lut_g[i] << 8) |
 			   intel_crtc->lut_b[i]);
 	}
+
+	if (reenable_ips)
+		hsw_enable_ips(crtc);
 }
 
 static void i845_update_cursor(struct drm_crtc *crtc, u32 base)
-- 
1.7.10.4