[RFC] drm/i915: Use DOUBLE_BUFFER_CTL instead of vblank evasion for GEN9+.

* [RFC] drm/i915: Use DOUBLE_BUFFER_CTL instead of vblank evasion for GEN9+.
@ 2018-02-08  8:55 Maarten Lankhorst
  2018-02-08  9:05 ` Chris Wilson
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Maarten Lankhorst @ 2018-02-08  8:55 UTC (permalink / raw)
  To: intel-gfx

References: https://bugs.freedesktop.org/show_bug.cgi?id=104975
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h      |  2 ++
 drivers/gpu/drm/i915/i915_reg.h      |  3 +++
 drivers/gpu/drm/i915/intel_display.c |  1 +
 drivers/gpu/drm/i915/intel_sprite.c  | 16 ++++++++++++++++
 4 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d5e695da2fc4..11251e0107f4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1967,6 +1967,8 @@ struct drm_i915_private {
 	/* Display functions */
 	struct drm_i915_display_funcs display;
 
+	spinlock_t display_evasion_lock;
+
 	/* PCH chipset type */
 	enum intel_pch pch_type;
 	unsigned short pch_id;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 93f6ec2ea8f2..20af56644844 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6594,6 +6594,9 @@ enum {
 #define  DIGITAL_PORTA_HOTPLUG_SHORT_DETECT	(1 << 0)
 #define  DIGITAL_PORTA_HOTPLUG_LONG_DETECT	(2 << 0)
 
+#define DOUBLE_BUFFER_CTL	_MMIO(0x44500)
+#define  DOUBLE_BUFFER_CTL_GLOBAL_DISABLE	(1 << 0)
+
 /* refresh rate hardware control */
 #define RR_HW_CTL       _MMIO(0x45300)
 #define  RR_HW_LOW_POWER_FRAMES_MASK    0xff
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 707406d1bf57..81087722bc49 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14476,6 +14476,7 @@ int intel_modeset_init(struct drm_device *dev)
 	dev_priv->modeset_wq = alloc_ordered_workqueue("i915_modeset", 0);
 
 	drm_mode_config_init(dev);
+	spin_lock_init(&dev_priv->display_evasion_lock);
 
 	dev->mode_config.min_width = 0;
 	dev->mode_config.min_height = 0;
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index ac0a4f9c1954..4d1e9b166d57 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -98,6 +98,13 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state)
 		intel_crtc_has_type(new_crtc_state, INTEL_OUTPUT_DSI);
 	DEFINE_WAIT(wait);
 
+	if (INTEL_GEN(dev_priv) >= 9) {
+		spin_lock_irq(&dev_priv->display_evasion_lock);
+		I915_WRITE(DOUBLE_BUFFER_CTL, DOUBLE_BUFFER_CTL_GLOBAL_DISABLE);
+		scanline = intel_get_crtc_scanline(crtc);
+		goto done;
+	}
+
 	vblank_start = adjusted_mode->crtc_vblank_start;
 	if (adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE)
 		vblank_start = DIV_ROUND_UP(vblank_start, 2);
@@ -166,6 +173,7 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state)
 	while (need_vlv_dsi_wa && scanline == vblank_start)
 		scanline = intel_get_crtc_scanline(crtc);
 
+done:
 	crtc->debug.scanline_start = scanline;
 	crtc->debug.start_vbl_time = ktime_get();
 	crtc->debug.start_vbl_count = intel_crtc_get_vblank_counter(crtc);
@@ -192,6 +200,9 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
 
 	trace_i915_pipe_update_end(crtc, end_vbl_count, scanline_end);
 
+	if (INTEL_GEN(dev_priv) >= 9)
+		I915_WRITE(DOUBLE_BUFFER_CTL, 0);
+
 	/* We're still in the vblank-evade critical section, this can't race.
 	 * Would be slightly nice to just grab the vblank count and arm the
 	 * event outside of the critical section - the spinlock might spin for a
@@ -206,6 +217,11 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
 		new_crtc_state->base.event = NULL;
 	}
 
+	if (INTEL_GEN(dev_priv) >= 9) {
+		spin_unlock_irq(&dev_priv->display_evasion_lock);
+		return;
+	}
+
 	local_irq_enable();
 
 	if (intel_vgpu_active(dev_priv))
-- 
2.16.1

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