drm/i915/overlay: Allocate physical registers from stolen

Given that we are now reasonably confident in our ability to detect and
reserve the stolen memory (physical memory reserved for graphics by the
BIOS) for ourselves on most machines, we can put it to use. In this
case, we need a page to hold the overlay registers.

On an i915g running MythTv, H Buus noticed that

	commit 6a2c4232
	Author: Chris Wilson <chris@chris-wilson.co.uk>
	Date:   Tue Nov 4 04:51:40 2014 -0800
	drm/i915: Make the physical object coherent with GTT

introduced stuttering into his video playback. After discarding the
likely suspect of it being the physical cursor updates, we were left
with the use of the phys object for the overlay. And lo, if we
completely avoid using the phys object (allocated just once on module
load!) by switching to stolen memory, the stuttering goes away.

For lack of a better explanation, claim victory and kill two birds with
one stone.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107600
Fixes: 6a2c4232 ("drm/i915: Make the physical object coherent with GTT")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180906190144.1272-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_overlay.c

@@ -181,8 +181,9 @@ struct intel_overlay {
 	u32 brightness, contrast, saturation;
 	u32 old_xscale, old_yscale;
 	/* register access */
-	u32 flip_addr;
 	struct drm_i915_gem_object *reg_bo;
+	struct overlay_registers __iomem *regs;
+	u32 flip_addr;
 	/* flip handling */
 	struct i915_gem_active last_flip;
 };
@@ -210,29 +211,6 @@ static void i830_overlay_clock_gating(struct drm_i915_private *dev_priv,
 				  PCI_DEVFN(0, 0), I830_CLOCK_GATE, val);
 }
 
-static struct overlay_registers __iomem *
-intel_overlay_map_regs(struct intel_overlay *overlay)
-{
-	struct drm_i915_private *dev_priv = overlay->i915;
-	struct overlay_registers __iomem *regs;
-
-	if (OVERLAY_NEEDS_PHYSICAL(dev_priv))
-		regs = (struct overlay_registers __iomem *)overlay->reg_bo->phys_handle->vaddr;
-	else
-		regs = io_mapping_map_wc(&dev_priv->ggtt.iomap,
-					 overlay->flip_addr,
-					 PAGE_SIZE);
-
-	return regs;
-}
-
-static void intel_overlay_unmap_regs(struct intel_overlay *overlay,
-				     struct overlay_registers __iomem *regs)
-{
-	if (!OVERLAY_NEEDS_PHYSICAL(overlay->i915))
-		io_mapping_unmap(regs);
-}
-
 static void intel_overlay_submit_request(struct intel_overlay *overlay,
 					 struct i915_request *rq,
 					 i915_gem_retire_fn retire)
@@ -784,13 +762,13 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 				      struct drm_i915_gem_object *new_bo,
 				      struct put_image_params *params)
 {
-	int ret, tmp_width;
-	struct overlay_registers __iomem *regs;
-	bool scale_changed = false;
+	struct overlay_registers __iomem *regs = overlay->regs;
 	struct drm_i915_private *dev_priv = overlay->i915;
 	u32 swidth, swidthsw, sheight, ostride;
 	enum pipe pipe = overlay->crtc->pipe;
+	bool scale_changed = false;
 	struct i915_vma *vma;
+	int ret, tmp_width;
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 	WARN_ON(!drm_modeset_is_locked(&dev_priv->drm.mode_config.connection_mutex));
@@ -815,30 +793,19 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 
 	if (!overlay->active) {
 		u32 oconfig;
-		regs = intel_overlay_map_regs(overlay);
-		if (!regs) {
-			ret = -ENOMEM;
-			goto out_unpin;
-		}
+
 		oconfig = OCONF_CC_OUT_8BIT;
 		if (IS_GEN4(dev_priv))
 			oconfig |= OCONF_CSC_MODE_BT709;
 		oconfig |= pipe == 0 ?
 			OCONF_PIPE_A : OCONF_PIPE_B;
 		iowrite32(oconfig, &regs->OCONFIG);
-		intel_overlay_unmap_regs(overlay, regs);
 
 		ret = intel_overlay_on(overlay);
 		if (ret != 0)
 			goto out_unpin;
 	}
 
-	regs = intel_overlay_map_regs(overlay);
-	if (!regs) {
-		ret = -ENOMEM;
-		goto out_unpin;
-	}
-
 	iowrite32((params->dst_y << 16) | params->dst_x, &regs->DWINPOS);
 	iowrite32((params->dst_h << 16) | params->dst_w, &regs->DWINSZ);
 
@@ -882,8 +849,6 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 
 	iowrite32(overlay_cmd_reg(params), &regs->OCMD);
 
-	intel_overlay_unmap_regs(overlay, regs);
-
 	ret = intel_overlay_continue(overlay, vma, scale_changed);
 	if (ret)
 		goto out_unpin;
@@ -901,7 +866,6 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 int intel_overlay_switch_off(struct intel_overlay *overlay)
 {
 	struct drm_i915_private *dev_priv = overlay->i915;
-	struct overlay_registers __iomem *regs;
 	int ret;
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
@@ -918,9 +882,7 @@ int intel_overlay_switch_off(struct intel_overlay *overlay)
 	if (ret != 0)
 		return ret;
 
-	regs = intel_overlay_map_regs(overlay);
-	iowrite32(0, &regs->OCMD);
-	intel_overlay_unmap_regs(overlay, regs);
+	iowrite32(0, &overlay->regs->OCMD);
 
 	return intel_overlay_off(overlay);
 }
@@ -1305,7 +1267,6 @@ int intel_overlay_attrs_ioctl(struct drm_device *dev, void *data,
 	struct drm_intel_overlay_attrs *attrs = data;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_overlay *overlay;
-	struct overlay_registers __iomem *regs;
 	int ret;
 
 	overlay = dev_priv->overlay;
@@ -1345,15 +1306,7 @@ int intel_overlay_attrs_ioctl(struct drm_device *dev, void *data,
 		overlay->contrast   = attrs->contrast;
 		overlay->saturation = attrs->saturation;
 
-		regs = intel_overlay_map_regs(overlay);
-		if (!regs) {
-			ret = -ENOMEM;
-			goto out_unlock;
-		}
-
-		update_reg_attrs(overlay, regs);
-
-		intel_overlay_unmap_regs(overlay, regs);
+		update_reg_attrs(overlay, overlay->regs);
 
 		if (attrs->flags & I915_OVERLAY_UPDATE_GAMMA) {
 			if (IS_GEN2(dev_priv))
@@ -1386,12 +1339,47 @@ int intel_overlay_attrs_ioctl(struct drm_device *dev, void *data,
 	return ret;
 }
 
+static int get_registers(struct intel_overlay *overlay, bool use_phys)
+{
+	struct drm_i915_gem_object *obj;
+	struct i915_vma *vma;
+	int err;
+
+	obj = i915_gem_object_create_stolen(overlay->i915, PAGE_SIZE);
+	if (obj == NULL)
+		obj = i915_gem_object_create_internal(overlay->i915, PAGE_SIZE);
+	if (IS_ERR(obj))
+		return PTR_ERR(obj);
+
+	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, PIN_MAPPABLE);
+	if (IS_ERR(vma)) {
+		err = PTR_ERR(vma);
+		goto err_put_bo;
+	}
+
+	if (use_phys)
+		overlay->flip_addr = sg_dma_address(obj->mm.pages->sgl);
+	else
+		overlay->flip_addr = i915_ggtt_offset(vma);
+	overlay->regs = i915_vma_pin_iomap(vma);
+	i915_vma_unpin(vma);
+
+	if (IS_ERR(overlay->regs)) {
+		err = PTR_ERR(overlay->regs);
+		goto err_put_bo;
+	}
+
+	overlay->reg_bo = obj;
+	return 0;
+
+err_put_bo:
+	i915_gem_object_put(obj);
+	return err;
+}
+
 void intel_setup_overlay(struct drm_i915_private *dev_priv)
 {
 	struct intel_overlay *overlay;
-	struct drm_i915_gem_object *reg_bo;
-	struct overlay_registers __iomem *regs;
-	struct i915_vma *vma = NULL;
 	int ret;
 
 	if (!HAS_OVERLAY(dev_priv))
@@ -1401,46 +1389,8 @@ void intel_setup_overlay(struct drm_i915_private *dev_priv)
 	if (!overlay)
 		return;
 
-	mutex_lock(&dev_priv->drm.struct_mutex);
-	if (WARN_ON(dev_priv->overlay))
-		goto out_free;
-
 	overlay->i915 = dev_priv;
 
-	reg_bo = NULL;
-	if (!OVERLAY_NEEDS_PHYSICAL(dev_priv))
-		reg_bo = i915_gem_object_create_stolen(dev_priv, PAGE_SIZE);
-	if (reg_bo == NULL)
-		reg_bo = i915_gem_object_create(dev_priv, PAGE_SIZE);
-	if (IS_ERR(reg_bo))
-		goto out_free;
-	overlay->reg_bo = reg_bo;
-
-	if (OVERLAY_NEEDS_PHYSICAL(dev_priv)) {
-		ret = i915_gem_object_attach_phys(reg_bo, PAGE_SIZE);
-		if (ret) {
-			DRM_ERROR("failed to attach phys overlay regs\n");
-			goto out_free_bo;
-		}
-		overlay->flip_addr = reg_bo->phys_handle->busaddr;
-	} else {
-		vma = i915_gem_object_ggtt_pin(reg_bo, NULL,
-					       0, PAGE_SIZE, PIN_MAPPABLE);
-		if (IS_ERR(vma)) {
-			DRM_ERROR("failed to pin overlay register bo\n");
-			ret = PTR_ERR(vma);
-			goto out_free_bo;
-		}
-		overlay->flip_addr = i915_ggtt_offset(vma);
-
-		ret = i915_gem_object_set_to_gtt_domain(reg_bo, true);
-		if (ret) {
-			DRM_ERROR("failed to move overlay register bo into the GTT\n");
-			goto out_unpin_bo;
-		}
-	}
-
-	/* init all values */
 	overlay->color_key = 0x0101fe;
 	overlay->color_key_enabled = true;
 	overlay->brightness = -19;
@@ -1449,44 +1399,51 @@ void intel_setup_overlay(struct drm_i915_private *dev_priv)
 
 	init_request_active(&overlay->last_flip, NULL);
 
-	regs = intel_overlay_map_regs(overlay);
-	if (!regs)
-		goto out_unpin_bo;
+	mutex_lock(&dev_priv->drm.struct_mutex);
+
+	ret = get_registers(overlay, OVERLAY_NEEDS_PHYSICAL(dev_priv));
+	if (ret)
+		goto out_free;
+
+	ret = i915_gem_object_set_to_gtt_domain(overlay->reg_bo, true);
+	if (ret)
+		goto out_reg_bo;
 
-	memset_io(regs, 0, sizeof(struct overlay_registers));
-	update_polyphase_filter(regs);
-	update_reg_attrs(overlay, regs);
+	mutex_unlock(&dev_priv->drm.struct_mutex);
 
-	intel_overlay_unmap_regs(overlay, regs);
+	memset_io(overlay->regs, 0, sizeof(struct overlay_registers));
+	update_polyphase_filter(overlay->regs);
+	update_reg_attrs(overlay, overlay->regs);
 
 	dev_priv->overlay = overlay;
-	mutex_unlock(&dev_priv->drm.struct_mutex);
-	DRM_INFO("initialized overlay support\n");
+	DRM_INFO("Initialized overlay support.\n");
 	return;
 
-out_unpin_bo:
-	if (vma)
-		i915_vma_unpin(vma);
-out_free_bo:
-	i915_gem_object_put(reg_bo);
+out_reg_bo:
+	i915_gem_object_put(overlay->reg_bo);
 out_free:
 	mutex_unlock(&dev_priv->drm.struct_mutex);
 	kfree(overlay);
-	return;
 }
 
 void intel_cleanup_overlay(struct drm_i915_private *dev_priv)
 {
-	if (!dev_priv->overlay)
+	struct intel_overlay *overlay;
+
+	overlay = fetch_and_zero(&dev_priv->overlay);
+	if (!overlay)
 		return;
 
-	/* The bo's should be free'd by the generic code already.
+	/*
+	 * The bo's should be free'd by the generic code already.
 	 * Furthermore modesetting teardown happens beforehand so the
-	 * hardware should be off already */
-	WARN_ON(dev_priv->overlay->active);
+	 * hardware should be off already.
+	 */
+	WARN_ON(overlay->active);
+
+	i915_gem_object_put(overlay->reg_bo);
 
-	i915_gem_object_put(dev_priv->overlay->reg_bo);
-	kfree(dev_priv->overlay);
+	kfree(overlay);
 }
 
 #if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
@@ -1498,37 +1455,11 @@ struct intel_overlay_error_state {
 	u32 isr;
 };
 
-static struct overlay_registers __iomem *
-intel_overlay_map_regs_atomic(struct intel_overlay *overlay)
-{
-	struct drm_i915_private *dev_priv = overlay->i915;
-	struct overlay_registers __iomem *regs;
-
-	if (OVERLAY_NEEDS_PHYSICAL(dev_priv))
-		/* Cast to make sparse happy, but it's wc memory anyway, so
-		 * equivalent to the wc io mapping on X86. */
-		regs = (struct overlay_registers __iomem *)
-			overlay->reg_bo->phys_handle->vaddr;
-	else
-		regs = io_mapping_map_atomic_wc(&dev_priv->ggtt.iomap,
-						overlay->flip_addr);
-
-	return regs;
-}
-
-static void intel_overlay_unmap_regs_atomic(struct intel_overlay *overlay,
-					struct overlay_registers __iomem *regs)
-{
-	if (!OVERLAY_NEEDS_PHYSICAL(overlay->i915))
-		io_mapping_unmap_atomic(regs);
-}
-
 struct intel_overlay_error_state *
 intel_overlay_capture_error_state(struct drm_i915_private *dev_priv)
 {
 	struct intel_overlay *overlay = dev_priv->overlay;
 	struct intel_overlay_error_state *error;
-	struct overlay_registers __iomem *regs;
 
 	if (!overlay || !overlay->active)
 		return NULL;
@@ -1541,18 +1472,9 @@ intel_overlay_capture_error_state(struct drm_i915_private *dev_priv)
 	error->isr = I915_READ(ISR);
 	error->base = overlay->flip_addr;
 
-	regs = intel_overlay_map_regs_atomic(overlay);
-	if (!regs)
-		goto err;
-
-	memcpy_fromio(&error->regs, regs, sizeof(struct overlay_registers));
-	intel_overlay_unmap_regs_atomic(overlay, regs);
+	memcpy_fromio(&error->regs, overlay->regs, sizeof(error->regs));
 
 	return error;
-
-err:
-	kfree(error);
-	return NULL;
 }
 
 void