[RFC 7/8] drm/i915: Allow final wm programming to be scheduled after next vblank (v2)

[Matt Roper <matthew.d.roper@intel.com>]

Add a simple mechanism to trigger final watermark updates in an
asynchronous manner once the next vblank occurs.  No platform types
actually support atomic watermark programming until a future patch, so
there should be no functional change yet; individual platforms will be
converted to use this mechanism one-by-one in future patches.

Note that we'll probably expand this to cover other post-vblank async
tasks (like unpinning) at some point in the future.

v2: Much simpler vblank mechanism than was used in the previous series;
    no need to allocate new heap structures.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h      |  7 +++++++
 drivers/gpu/drm/i915/i915_irq.c      |  9 +++++++++
 drivers/gpu/drm/i915/intel_display.c | 30 ++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/intel_drv.h     |  4 ++++
 4 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2774976..5ad942e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -628,6 +628,7 @@ struct drm_i915_display_funcs {
 				 struct drm_crtc *crtc,
 				 uint32_t sprite_width, uint32_t sprite_height,
 				 int pixel_size, bool enable, bool scaled);
+	void (*program_watermarks)(struct drm_i915_private *dev_priv);
 	int (*modeset_calc_cdclk)(struct drm_atomic_state *state);
 	void (*modeset_commit_cdclk)(struct drm_atomic_state *state);
 	/* Returns the active state of the crtc, and if the crtc is active,
@@ -2567,6 +2568,12 @@ struct drm_i915_cmd_table {
 #define HAS_L3_DPF(dev) (IS_IVYBRIDGE(dev) || IS_HASWELL(dev))
 #define NUM_L3_SLICES(dev) (IS_HSW_GT3(dev) ? 2 : HAS_L3_DPF(dev))
 
+/*
+ * FIXME:  Not all platforms have been transitioned to atomic watermark
+ * updates yet.
+ */
+#define HAS_ATOMIC_WM(dev_priv) (dev_priv->display.program_watermarks != NULL)
+
 #define GT_FREQUENCY_MULTIPLIER 50
 #define GEN9_FREQ_SCALER 3
 
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index a6fbe64..20c7260 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1452,6 +1452,15 @@ static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir)
 
 static bool intel_pipe_handle_vblank(struct drm_device *dev, enum pipe pipe)
 {
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+
+	if (intel_crtc->need_vblank_wm_update) {
+		queue_work(dev_priv->wq, &intel_crtc->wm_work);
+		intel_crtc->need_vblank_wm_update = false;
+	}
+
 	if (!drm_handle_vblank(dev, pipe))
 		return false;
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 46b62cc..fa4373e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4737,6 +4737,10 @@ static void intel_post_plane_update(struct intel_crtc *crtc)
 	struct drm_device *dev = crtc->base.dev;
 	struct drm_plane *plane;
 
+	if (HAS_ATOMIC_WM(to_i915(dev)))
+		/* vblank handler will kick off workqueue task to update wm's */
+		crtc->need_vblank_wm_update = true;
+
 	if (atomic->wait_vblank)
 		intel_wait_for_vblank(dev, crtc->pipe);
 
@@ -4745,7 +4749,7 @@ static void intel_post_plane_update(struct intel_crtc *crtc)
 	if (atomic->disable_cxsr)
 		cstate->wm.cxsr_allowed = true;
 
-	if (crtc->atomic.update_wm_post)
+	if (!HAS_ATOMIC_WM(to_i915(dev)) && crtc->atomic.update_wm_post)
 		intel_update_watermarks(&crtc->base);
 
 	if (atomic->update_fbc) {
@@ -4757,9 +4761,10 @@ static void intel_post_plane_update(struct intel_crtc *crtc)
 	if (atomic->post_enable_primary)
 		intel_post_enable_primary(&crtc->base);
 
-	drm_for_each_plane_mask(plane, dev, atomic->update_sprite_watermarks)
-		intel_update_sprite_watermarks(plane, &crtc->base,
-					       0, 0, 0, false, false);
+	if (!HAS_ATOMIC_WM(to_i915(dev)))
+		drm_for_each_plane_mask(plane, dev, atomic->update_sprite_watermarks)
+			intel_update_sprite_watermarks(plane, &crtc->base,
+						       0, 0, 0, false, false);
 
 	memset(atomic, 0, sizeof(*atomic));
 }
@@ -14070,6 +14075,21 @@ static void skl_init_scalers(struct drm_device *dev, struct intel_crtc *intel_cr
 	scaler_state->scaler_id = -1;
 }
 
+/* FIXME: This may expand to cover other tasks like unpinning in the future... */
+static void wm_work_func(struct work_struct *work)
+{
+	struct intel_crtc *intel_crtc =
+		container_of(work, struct intel_crtc, wm_work);
+	struct drm_i915_private *dev_priv = to_i915(intel_crtc->base.dev);
+
+	if (WARN_ON(!HAS_ATOMIC_WM(dev_priv)))
+		return;
+	if (WARN_ON(!intel_crtc->base.state->active))
+		return;
+
+	dev_priv->display.program_watermarks(dev_priv);
+}
+
 static void intel_crtc_init(struct drm_device *dev, int pipe)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -14142,6 +14162,8 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
 	dev_priv->plane_to_crtc_mapping[intel_crtc->plane] = &intel_crtc->base;
 	dev_priv->pipe_to_crtc_mapping[intel_crtc->pipe] = &intel_crtc->base;
 
+	INIT_WORK(&intel_crtc->wm_work, wm_work_func);
+
 	drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
 
 	WARN_ON(drm_crtc_index(&intel_crtc->base) != intel_crtc->pipe);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 335b24b..775e3d0 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -586,6 +586,10 @@ struct intel_crtc {
 	int num_scalers;
 
 	struct vlv_wm_state wm_state;
+
+	/* Do we need to program watermark values after the next vblank? */
+	bool need_vblank_wm_update;
+	struct work_struct wm_work;
 };
 
 struct intel_plane_wm_parameters {
-- 
2.1.4

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