[PATCH 1/3] drm/i915: Clean up Makefile

[PATCH 1/3] drm/i915: Clean up Makefile

[Daniel Vetter]

Sorting became confused and a few new files ended up in strange
places. Also move i915_irq.c to core since with the recent-ish
extraction of i915_gpu_error.c and intel_hotplug.c it's more and more
really just basic irq handling code.

When adding new files please don't put them somewhere randomly.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/Makefile | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index e52e01251644..bf91482e14a3 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -6,12 +6,13 @@
 
 # core driver code
 i915-y := i915_drv.o \
+	  i915_irq.o \
 	  i915_params.o \
           i915_suspend.o \
 	  i915_sysfs.o \
+	  intel_csr.o \
 	  intel_pm.o \
-	  intel_runtime_pm.o \
-	  intel_csr.o
+	  intel_runtime_pm.o
 
 i915-$(CONFIG_COMPAT)   += i915_ioc32.o
 i915-$(CONFIG_DEBUG_FS) += i915_debugfs.o
@@ -20,21 +21,19 @@ i915-$(CONFIG_DEBUG_FS) += i915_debugfs.o
 i915-y += i915_cmd_parser.o \
 	  i915_gem_batch_pool.o \
 	  i915_gem_context.o \
-	  i915_gem_render_state.o \
 	  i915_gem_debug.o \
 	  i915_gem_dmabuf.o \
 	  i915_gem_evict.o \
 	  i915_gem_execbuffer.o \
 	  i915_gem_gtt.o \
 	  i915_gem.o \
+	  i915_gem_render_state.o \
 	  i915_gem_shrinker.o \
 	  i915_gem_stolen.o \
 	  i915_gem_tiling.o \
 	  i915_gem_userptr.o \
 	  i915_gpu_error.o \
-	  i915_irq.o \
 	  i915_trace_points.o \
-	  intel_hotplug.o \
 	  intel_lrc.o \
 	  intel_mocs.o \
 	  intel_ringbuffer.o \
@@ -48,11 +47,14 @@ i915-y += intel_renderstate_gen6.o \
 
 # modesetting core code
 i915-y += intel_audio.o \
+	  intel_atomic.o \
+	  intel_atomic_plane.o \
 	  intel_bios.o \
 	  intel_display.o \
 	  intel_fbc.o \
 	  intel_fifo_underrun.o \
 	  intel_frontbuffer.o \
+	  intel_hotplug.o \
 	  intel_modes.o \
 	  intel_overlay.o \
 	  intel_psr.o \
@@ -68,15 +70,13 @@ i915-y += dvo_ch7017.o \
 	  dvo_ns2501.o \
 	  dvo_sil164.o \
 	  dvo_tfp410.o \
-	  intel_atomic.o \
-	  intel_atomic_plane.o \
 	  intel_crt.o \
 	  intel_ddi.o \
-	  intel_dp.o \
 	  intel_dp_mst.o \
+	  intel_dp.o \
 	  intel_dsi.o \
-	  intel_dsi_pll.o \
 	  intel_dsi_panel_vbt.o \
+	  intel_dsi_pll.o \
 	  intel_dvo.o \
 	  intel_hdmi.o \
 	  intel_i2c.o \
-- 
2.1.4

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[PATCH 2/3] drm/i915: Extract i915_gem_fence.c

[Daniel Vetter]

No code changes, just moving all the fence related code into a
separate file (and avoiding a bunch of forward declarations while at
it).

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/Makefile         |   1 +
 drivers/gpu/drm/i915/i915_drv.h       |  16 +-
 drivers/gpu/drm/i915/i915_gem.c       | 401 --------------------------------
 drivers/gpu/drm/i915/i915_gem_fence.c | 422 ++++++++++++++++++++++++++++++++++
 4 files changed, 432 insertions(+), 408 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_gem_fence.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index bf91482e14a3..41fb8a9c5bef 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -25,6 +25,7 @@ i915-y += i915_cmd_parser.o \
 	  i915_gem_dmabuf.o \
 	  i915_gem_evict.o \
 	  i915_gem_execbuffer.o \
+	  i915_gem_fence.o \
 	  i915_gem_gtt.o \
 	  i915_gem.o \
 	  i915_gem_render_state.o \
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 773883d54b28..4c34fb15d0df 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2858,11 +2858,6 @@ static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req,
 
 int __must_check i915_gem_get_seqno(struct drm_device *dev, u32 *seqno);
 int __must_check i915_gem_set_seqno(struct drm_device *dev, u32 seqno);
-int __must_check i915_gem_object_get_fence(struct drm_i915_gem_object *obj);
-int __must_check i915_gem_object_put_fence(struct drm_i915_gem_object *obj);
-
-bool i915_gem_object_pin_fence(struct drm_i915_gem_object *obj);
-void i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj);
 
 struct drm_i915_gem_request *
 i915_gem_find_active_request(struct intel_engine_cs *ring);
@@ -2960,8 +2955,6 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 				struct drm_gem_object *gem_obj, int flags);
 
-void i915_gem_restore_fences(struct drm_device *dev);
-
 unsigned long
 i915_gem_obj_ggtt_offset_view(struct drm_i915_gem_object *o,
 			      const struct i915_ggtt_view *view);
@@ -3056,6 +3049,15 @@ i915_gem_object_ggtt_unpin(struct drm_i915_gem_object *obj)
 	i915_gem_object_ggtt_unpin_view(obj, &i915_ggtt_view_normal);
 }
 
+/* i915_gem_fence.c */
+int __must_check i915_gem_object_get_fence(struct drm_i915_gem_object *obj);
+int __must_check i915_gem_object_put_fence(struct drm_i915_gem_object *obj);
+
+bool i915_gem_object_pin_fence(struct drm_i915_gem_object *obj);
+void i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj);
+
+void i915_gem_restore_fences(struct drm_device *dev);
+
 /* i915_gem_context.c */
 int __must_check i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 322bbefafbc3..5d685789b1f9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -46,11 +46,6 @@ static void
 i915_gem_object_retire__write(struct drm_i915_gem_object *obj);
 static void
 i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring);
-static void i915_gem_write_fence(struct drm_device *dev, int reg,
-				 struct drm_i915_gem_object *obj);
-static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
-					 struct drm_i915_fence_reg *fence,
-					 bool enable);
 
 static bool cpu_cache_is_coherent(struct drm_device *dev,
 				  enum i915_cache_level level)
@@ -66,18 +61,6 @@ static bool cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 	return obj->pin_display;
 }
 
-static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
-{
-	if (obj->tiling_mode)
-		i915_gem_release_mmap(obj);
-
-	/* As we do not have an associated fence register, we will force
-	 * a tiling change if we ever need to acquire one.
-	 */
-	obj->fence_dirty = false;
-	obj->fence_reg = I915_FENCE_REG_NONE;
-}
-
 /* some bookkeeping */
 static void i915_gem_info_add_obj(struct drm_i915_private *dev_priv,
 				  size_t size)
@@ -2793,27 +2776,6 @@ static void i915_gem_reset_ring_cleanup(struct drm_i915_private *dev_priv,
 	}
 }
 
-void i915_gem_restore_fences(struct drm_device *dev)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	int i;
-
-	for (i = 0; i < dev_priv->num_fence_regs; i++) {
-		struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
-
-		/*
-		 * Commit delayed tiling changes if we have an object still
-		 * attached to the fence, otherwise just clear the fence.
-		 */
-		if (reg->obj) {
-			i915_gem_object_update_fence(reg->obj, reg,
-						     reg->obj->tiling_mode);
-		} else {
-			i915_gem_write_fence(dev, i, NULL);
-		}
-	}
-}
-
 void i915_gem_reset(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -3340,343 +3302,6 @@ int i915_gpu_idle(struct drm_device *dev)
 	return 0;
 }
 
-static void i965_write_fence_reg(struct drm_device *dev, int reg,
-				 struct drm_i915_gem_object *obj)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	int fence_reg;
-	int fence_pitch_shift;
-
-	if (INTEL_INFO(dev)->gen >= 6) {
-		fence_reg = FENCE_REG_SANDYBRIDGE_0;
-		fence_pitch_shift = SANDYBRIDGE_FENCE_PITCH_SHIFT;
-	} else {
-		fence_reg = FENCE_REG_965_0;
-		fence_pitch_shift = I965_FENCE_PITCH_SHIFT;
-	}
-
-	fence_reg += reg * 8;
-
-	/* To w/a incoherency with non-atomic 64-bit register updates,
-	 * we split the 64-bit update into two 32-bit writes. In order
-	 * for a partial fence not to be evaluated between writes, we
-	 * precede the update with write to turn off the fence register,
-	 * and only enable the fence as the last step.
-	 *
-	 * For extra levels of paranoia, we make sure each step lands
-	 * before applying the next step.
-	 */
-	I915_WRITE(fence_reg, 0);
-	POSTING_READ(fence_reg);
-
-	if (obj) {
-		u32 size = i915_gem_obj_ggtt_size(obj);
-		uint64_t val;
-
-		/* Adjust fence size to match tiled area */
-		if (obj->tiling_mode != I915_TILING_NONE) {
-			uint32_t row_size = obj->stride *
-				(obj->tiling_mode == I915_TILING_Y ? 32 : 8);
-			size = (size / row_size) * row_size;
-		}
-
-		val = (uint64_t)((i915_gem_obj_ggtt_offset(obj) + size - 4096) &
-				 0xfffff000) << 32;
-		val |= i915_gem_obj_ggtt_offset(obj) & 0xfffff000;
-		val |= (uint64_t)((obj->stride / 128) - 1) << fence_pitch_shift;
-		if (obj->tiling_mode == I915_TILING_Y)
-			val |= 1 << I965_FENCE_TILING_Y_SHIFT;
-		val |= I965_FENCE_REG_VALID;
-
-		I915_WRITE(fence_reg + 4, val >> 32);
-		POSTING_READ(fence_reg + 4);
-
-		I915_WRITE(fence_reg + 0, val);
-		POSTING_READ(fence_reg);
-	} else {
-		I915_WRITE(fence_reg + 4, 0);
-		POSTING_READ(fence_reg + 4);
-	}
-}
-
-static void i915_write_fence_reg(struct drm_device *dev, int reg,
-				 struct drm_i915_gem_object *obj)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 val;
-
-	if (obj) {
-		u32 size = i915_gem_obj_ggtt_size(obj);
-		int pitch_val;
-		int tile_width;
-
-		WARN((i915_gem_obj_ggtt_offset(obj) & ~I915_FENCE_START_MASK) ||
-		     (size & -size) != size ||
-		     (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
-		     "object 0x%08lx [fenceable? %d] not 1M or pot-size (0x%08x) aligned\n",
-		     i915_gem_obj_ggtt_offset(obj), obj->map_and_fenceable, size);
-
-		if (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
-			tile_width = 128;
-		else
-			tile_width = 512;
-
-		/* Note: pitch better be a power of two tile widths */
-		pitch_val = obj->stride / tile_width;
-		pitch_val = ffs(pitch_val) - 1;
-
-		val = i915_gem_obj_ggtt_offset(obj);
-		if (obj->tiling_mode == I915_TILING_Y)
-			val |= 1 << I830_FENCE_TILING_Y_SHIFT;
-		val |= I915_FENCE_SIZE_BITS(size);
-		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
-		val |= I830_FENCE_REG_VALID;
-	} else
-		val = 0;
-
-	if (reg < 8)
-		reg = FENCE_REG_830_0 + reg * 4;
-	else
-		reg = FENCE_REG_945_8 + (reg - 8) * 4;
-
-	I915_WRITE(reg, val);
-	POSTING_READ(reg);
-}
-
-static void i830_write_fence_reg(struct drm_device *dev, int reg,
-				struct drm_i915_gem_object *obj)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	uint32_t val;
-
-	if (obj) {
-		u32 size = i915_gem_obj_ggtt_size(obj);
-		uint32_t pitch_val;
-
-		WARN((i915_gem_obj_ggtt_offset(obj) & ~I830_FENCE_START_MASK) ||
-		     (size & -size) != size ||
-		     (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
-		     "object 0x%08lx not 512K or pot-size 0x%08x aligned\n",
-		     i915_gem_obj_ggtt_offset(obj), size);
-
-		pitch_val = obj->stride / 128;
-		pitch_val = ffs(pitch_val) - 1;
-
-		val = i915_gem_obj_ggtt_offset(obj);
-		if (obj->tiling_mode == I915_TILING_Y)
-			val |= 1 << I830_FENCE_TILING_Y_SHIFT;
-		val |= I830_FENCE_SIZE_BITS(size);
-		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
-		val |= I830_FENCE_REG_VALID;
-	} else
-		val = 0;
-
-	I915_WRITE(FENCE_REG_830_0 + reg * 4, val);
-	POSTING_READ(FENCE_REG_830_0 + reg * 4);
-}
-
-inline static bool i915_gem_object_needs_mb(struct drm_i915_gem_object *obj)
-{
-	return obj && obj->base.read_domains & I915_GEM_DOMAIN_GTT;
-}
-
-static void i915_gem_write_fence(struct drm_device *dev, int reg,
-				 struct drm_i915_gem_object *obj)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-
-	/* Ensure that all CPU reads are completed before installing a fence
-	 * and all writes before removing the fence.
-	 */
-	if (i915_gem_object_needs_mb(dev_priv->fence_regs[reg].obj))
-		mb();
-
-	WARN(obj && (!obj->stride || !obj->tiling_mode),
-	     "bogus fence setup with stride: 0x%x, tiling mode: %i\n",
-	     obj->stride, obj->tiling_mode);
-
-	if (IS_GEN2(dev))
-		i830_write_fence_reg(dev, reg, obj);
-	else if (IS_GEN3(dev))
-		i915_write_fence_reg(dev, reg, obj);
-	else if (INTEL_INFO(dev)->gen >= 4)
-		i965_write_fence_reg(dev, reg, obj);
-
-	/* And similarly be paranoid that no direct access to this region
-	 * is reordered to before the fence is installed.
-	 */
-	if (i915_gem_object_needs_mb(obj))
-		mb();
-}
-
-static inline int fence_number(struct drm_i915_private *dev_priv,
-			       struct drm_i915_fence_reg *fence)
-{
-	return fence - dev_priv->fence_regs;
-}
-
-static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
-					 struct drm_i915_fence_reg *fence,
-					 bool enable)
-{
-	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
-	int reg = fence_number(dev_priv, fence);
-
-	i915_gem_write_fence(obj->base.dev, reg, enable ? obj : NULL);
-
-	if (enable) {
-		obj->fence_reg = reg;
-		fence->obj = obj;
-		list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
-	} else {
-		obj->fence_reg = I915_FENCE_REG_NONE;
-		fence->obj = NULL;
-		list_del_init(&fence->lru_list);
-	}
-	obj->fence_dirty = false;
-}
-
-static int
-i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
-{
-	if (obj->last_fenced_req) {
-		int ret = i915_wait_request(obj->last_fenced_req);
-		if (ret)
-			return ret;
-
-		i915_gem_request_assign(&obj->last_fenced_req, NULL);
-	}
-
-	return 0;
-}
-
-int
-i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
-{
-	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
-	struct drm_i915_fence_reg *fence;
-	int ret;
-
-	ret = i915_gem_object_wait_fence(obj);
-	if (ret)
-		return ret;
-
-	if (obj->fence_reg == I915_FENCE_REG_NONE)
-		return 0;
-
-	fence = &dev_priv->fence_regs[obj->fence_reg];
-
-	if (WARN_ON(fence->pin_count))
-		return -EBUSY;
-
-	i915_gem_object_fence_lost(obj);
-	i915_gem_object_update_fence(obj, fence, false);
-
-	return 0;
-}
-
-static struct drm_i915_fence_reg *
-i915_find_fence_reg(struct drm_device *dev)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct drm_i915_fence_reg *reg, *avail;
-	int i;
-
-	/* First try to find a free reg */
-	avail = NULL;
-	for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {
-		reg = &dev_priv->fence_regs[i];
-		if (!reg->obj)
-			return reg;
-
-		if (!reg->pin_count)
-			avail = reg;
-	}
-
-	if (avail == NULL)
-		goto deadlock;
-
-	/* None available, try to steal one or wait for a user to finish */
-	list_for_each_entry(reg, &dev_priv->mm.fence_list, lru_list) {
-		if (reg->pin_count)
-			continue;
-
-		return reg;
-	}
-
-deadlock:
-	/* Wait for completion of pending flips which consume fences */
-	if (intel_has_pending_fb_unpin(dev))
-		return ERR_PTR(-EAGAIN);
-
-	return ERR_PTR(-EDEADLK);
-}
-
-/**
- * i915_gem_object_get_fence - set up fencing for an object
- * @obj: object to map through a fence reg
- *
- * When mapping objects through the GTT, userspace wants to be able to write
- * to them without having to worry about swizzling if the object is tiled.
- * This function walks the fence regs looking for a free one for @obj,
- * stealing one if it can't find any.
- *
- * It then sets up the reg based on the object's properties: address, pitch
- * and tiling format.
- *
- * For an untiled surface, this removes any existing fence.
- */
-int
-i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
-{
-	struct drm_device *dev = obj->base.dev;
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	bool enable = obj->tiling_mode != I915_TILING_NONE;
-	struct drm_i915_fence_reg *reg;
-	int ret;
-
-	/* Have we updated the tiling parameters upon the object and so
-	 * will need to serialise the write to the associated fence register?
-	 */
-	if (obj->fence_dirty) {
-		ret = i915_gem_object_wait_fence(obj);
-		if (ret)
-			return ret;
-	}
-
-	/* Just update our place in the LRU if our fence is getting reused. */
-	if (obj->fence_reg != I915_FENCE_REG_NONE) {
-		reg = &dev_priv->fence_regs[obj->fence_reg];
-		if (!obj->fence_dirty) {
-			list_move_tail(&reg->lru_list,
-				       &dev_priv->mm.fence_list);
-			return 0;
-		}
-	} else if (enable) {
-		if (WARN_ON(!obj->map_and_fenceable))
-			return -EINVAL;
-
-		reg = i915_find_fence_reg(dev);
-		if (IS_ERR(reg))
-			return PTR_ERR(reg);
-
-		if (reg->obj) {
-			struct drm_i915_gem_object *old = reg->obj;
-
-			ret = i915_gem_object_wait_fence(old);
-			if (ret)
-				return ret;
-
-			i915_gem_object_fence_lost(old);
-		}
-	} else
-		return 0;
-
-	i915_gem_object_update_fence(obj, reg, enable);
-
-	return 0;
-}
-
 static bool i915_gem_valid_gtt_space(struct i915_vma *vma,
 				     unsigned long cache_level)
 {
@@ -4476,32 +4101,6 @@ i915_gem_object_ggtt_unpin_view(struct drm_i915_gem_object *obj,
 	--vma->pin_count;
 }
 
-bool
-i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
-{
-	if (obj->fence_reg != I915_FENCE_REG_NONE) {
-		struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
-		struct i915_vma *ggtt_vma = i915_gem_obj_to_ggtt(obj);
-
-		WARN_ON(!ggtt_vma ||
-			dev_priv->fence_regs[obj->fence_reg].pin_count >
-			ggtt_vma->pin_count);
-		dev_priv->fence_regs[obj->fence_reg].pin_count++;
-		return true;
-	} else
-		return false;
-}
-
-void
-i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
-{
-	if (obj->fence_reg != I915_FENCE_REG_NONE) {
-		struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
-		WARN_ON(dev_priv->fence_regs[obj->fence_reg].pin_count <= 0);
-		dev_priv->fence_regs[obj->fence_reg].pin_count--;
-	}
-}
-
 int
 i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 		    struct drm_file *file)
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
new file mode 100644
index 000000000000..d3284ee04794
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -0,0 +1,422 @@
+/*
+ * Copyright © 2008-2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <drm/drmP.h>
+#include <drm/i915_drm.h>
+#include "i915_drv.h"
+
+static void i965_write_fence_reg(struct drm_device *dev, int reg,
+				 struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int fence_reg;
+	int fence_pitch_shift;
+
+	if (INTEL_INFO(dev)->gen >= 6) {
+		fence_reg = FENCE_REG_SANDYBRIDGE_0;
+		fence_pitch_shift = SANDYBRIDGE_FENCE_PITCH_SHIFT;
+	} else {
+		fence_reg = FENCE_REG_965_0;
+		fence_pitch_shift = I965_FENCE_PITCH_SHIFT;
+	}
+
+	fence_reg += reg * 8;
+
+	/* To w/a incoherency with non-atomic 64-bit register updates,
+	 * we split the 64-bit update into two 32-bit writes. In order
+	 * for a partial fence not to be evaluated between writes, we
+	 * precede the update with write to turn off the fence register,
+	 * and only enable the fence as the last step.
+	 *
+	 * For extra levels of paranoia, we make sure each step lands
+	 * before applying the next step.
+	 */
+	I915_WRITE(fence_reg, 0);
+	POSTING_READ(fence_reg);
+
+	if (obj) {
+		u32 size = i915_gem_obj_ggtt_size(obj);
+		uint64_t val;
+
+		/* Adjust fence size to match tiled area */
+		if (obj->tiling_mode != I915_TILING_NONE) {
+			uint32_t row_size = obj->stride *
+				(obj->tiling_mode == I915_TILING_Y ? 32 : 8);
+			size = (size / row_size) * row_size;
+		}
+
+		val = (uint64_t)((i915_gem_obj_ggtt_offset(obj) + size - 4096) &
+				 0xfffff000) << 32;
+		val |= i915_gem_obj_ggtt_offset(obj) & 0xfffff000;
+		val |= (uint64_t)((obj->stride / 128) - 1) << fence_pitch_shift;
+		if (obj->tiling_mode == I915_TILING_Y)
+			val |= 1 << I965_FENCE_TILING_Y_SHIFT;
+		val |= I965_FENCE_REG_VALID;
+
+		I915_WRITE(fence_reg + 4, val >> 32);
+		POSTING_READ(fence_reg + 4);
+
+		I915_WRITE(fence_reg + 0, val);
+		POSTING_READ(fence_reg);
+	} else {
+		I915_WRITE(fence_reg + 4, 0);
+		POSTING_READ(fence_reg + 4);
+	}
+}
+
+static void i915_write_fence_reg(struct drm_device *dev, int reg,
+				 struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 val;
+
+	if (obj) {
+		u32 size = i915_gem_obj_ggtt_size(obj);
+		int pitch_val;
+		int tile_width;
+
+		WARN((i915_gem_obj_ggtt_offset(obj) & ~I915_FENCE_START_MASK) ||
+		     (size & -size) != size ||
+		     (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
+		     "object 0x%08lx [fenceable? %d] not 1M or pot-size (0x%08x) aligned\n",
+		     i915_gem_obj_ggtt_offset(obj), obj->map_and_fenceable, size);
+
+		if (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
+			tile_width = 128;
+		else
+			tile_width = 512;
+
+		/* Note: pitch better be a power of two tile widths */
+		pitch_val = obj->stride / tile_width;
+		pitch_val = ffs(pitch_val) - 1;
+
+		val = i915_gem_obj_ggtt_offset(obj);
+		if (obj->tiling_mode == I915_TILING_Y)
+			val |= 1 << I830_FENCE_TILING_Y_SHIFT;
+		val |= I915_FENCE_SIZE_BITS(size);
+		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
+		val |= I830_FENCE_REG_VALID;
+	} else
+		val = 0;
+
+	if (reg < 8)
+		reg = FENCE_REG_830_0 + reg * 4;
+	else
+		reg = FENCE_REG_945_8 + (reg - 8) * 4;
+
+	I915_WRITE(reg, val);
+	POSTING_READ(reg);
+}
+
+static void i830_write_fence_reg(struct drm_device *dev, int reg,
+				struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	uint32_t val;
+
+	if (obj) {
+		u32 size = i915_gem_obj_ggtt_size(obj);
+		uint32_t pitch_val;
+
+		WARN((i915_gem_obj_ggtt_offset(obj) & ~I830_FENCE_START_MASK) ||
+		     (size & -size) != size ||
+		     (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
+		     "object 0x%08lx not 512K or pot-size 0x%08x aligned\n",
+		     i915_gem_obj_ggtt_offset(obj), size);
+
+		pitch_val = obj->stride / 128;
+		pitch_val = ffs(pitch_val) - 1;
+
+		val = i915_gem_obj_ggtt_offset(obj);
+		if (obj->tiling_mode == I915_TILING_Y)
+			val |= 1 << I830_FENCE_TILING_Y_SHIFT;
+		val |= I830_FENCE_SIZE_BITS(size);
+		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
+		val |= I830_FENCE_REG_VALID;
+	} else
+		val = 0;
+
+	I915_WRITE(FENCE_REG_830_0 + reg * 4, val);
+	POSTING_READ(FENCE_REG_830_0 + reg * 4);
+}
+
+inline static bool i915_gem_object_needs_mb(struct drm_i915_gem_object *obj)
+{
+	return obj && obj->base.read_domains & I915_GEM_DOMAIN_GTT;
+}
+
+static void i915_gem_write_fence(struct drm_device *dev, int reg,
+				 struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	/* Ensure that all CPU reads are completed before installing a fence
+	 * and all writes before removing the fence.
+	 */
+	if (i915_gem_object_needs_mb(dev_priv->fence_regs[reg].obj))
+		mb();
+
+	WARN(obj && (!obj->stride || !obj->tiling_mode),
+	     "bogus fence setup with stride: 0x%x, tiling mode: %i\n",
+	     obj->stride, obj->tiling_mode);
+
+	if (IS_GEN2(dev))
+		i830_write_fence_reg(dev, reg, obj);
+	else if (IS_GEN3(dev))
+		i915_write_fence_reg(dev, reg, obj);
+	else if (INTEL_INFO(dev)->gen >= 4)
+		i965_write_fence_reg(dev, reg, obj);
+
+	/* And similarly be paranoid that no direct access to this region
+	 * is reordered to before the fence is installed.
+	 */
+	if (i915_gem_object_needs_mb(obj))
+		mb();
+}
+
+static inline int fence_number(struct drm_i915_private *dev_priv,
+			       struct drm_i915_fence_reg *fence)
+{
+	return fence - dev_priv->fence_regs;
+}
+
+static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
+					 struct drm_i915_fence_reg *fence,
+					 bool enable)
+{
+	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+	int reg = fence_number(dev_priv, fence);
+
+	i915_gem_write_fence(obj->base.dev, reg, enable ? obj : NULL);
+
+	if (enable) {
+		obj->fence_reg = reg;
+		fence->obj = obj;
+		list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
+	} else {
+		obj->fence_reg = I915_FENCE_REG_NONE;
+		fence->obj = NULL;
+		list_del_init(&fence->lru_list);
+	}
+	obj->fence_dirty = false;
+}
+
+static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
+{
+	if (obj->tiling_mode)
+		i915_gem_release_mmap(obj);
+
+	/* As we do not have an associated fence register, we will force
+	 * a tiling change if we ever need to acquire one.
+	 */
+	obj->fence_dirty = false;
+	obj->fence_reg = I915_FENCE_REG_NONE;
+}
+
+static int
+i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
+{
+	if (obj->last_fenced_req) {
+		int ret = i915_wait_request(obj->last_fenced_req);
+		if (ret)
+			return ret;
+
+		i915_gem_request_assign(&obj->last_fenced_req, NULL);
+	}
+
+	return 0;
+}
+
+int
+i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+	struct drm_i915_fence_reg *fence;
+	int ret;
+
+	ret = i915_gem_object_wait_fence(obj);
+	if (ret)
+		return ret;
+
+	if (obj->fence_reg == I915_FENCE_REG_NONE)
+		return 0;
+
+	fence = &dev_priv->fence_regs[obj->fence_reg];
+
+	if (WARN_ON(fence->pin_count))
+		return -EBUSY;
+
+	i915_gem_object_fence_lost(obj);
+	i915_gem_object_update_fence(obj, fence, false);
+
+	return 0;
+}
+
+static struct drm_i915_fence_reg *
+i915_find_fence_reg(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_fence_reg *reg, *avail;
+	int i;
+
+	/* First try to find a free reg */
+	avail = NULL;
+	for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {
+		reg = &dev_priv->fence_regs[i];
+		if (!reg->obj)
+			return reg;
+
+		if (!reg->pin_count)
+			avail = reg;
+	}
+
+	if (avail == NULL)
+		goto deadlock;
+
+	/* None available, try to steal one or wait for a user to finish */
+	list_for_each_entry(reg, &dev_priv->mm.fence_list, lru_list) {
+		if (reg->pin_count)
+			continue;
+
+		return reg;
+	}
+
+deadlock:
+	/* Wait for completion of pending flips which consume fences */
+	if (intel_has_pending_fb_unpin(dev))
+		return ERR_PTR(-EAGAIN);
+
+	return ERR_PTR(-EDEADLK);
+}
+
+/**
+ * i915_gem_object_get_fence - set up fencing for an object
+ * @obj: object to map through a fence reg
+ *
+ * When mapping objects through the GTT, userspace wants to be able to write
+ * to them without having to worry about swizzling if the object is tiled.
+ * This function walks the fence regs looking for a free one for @obj,
+ * stealing one if it can't find any.
+ *
+ * It then sets up the reg based on the object's properties: address, pitch
+ * and tiling format.
+ *
+ * For an untiled surface, this removes any existing fence.
+ */
+int
+i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
+{
+	struct drm_device *dev = obj->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool enable = obj->tiling_mode != I915_TILING_NONE;
+	struct drm_i915_fence_reg *reg;
+	int ret;
+
+	/* Have we updated the tiling parameters upon the object and so
+	 * will need to serialise the write to the associated fence register?
+	 */
+	if (obj->fence_dirty) {
+		ret = i915_gem_object_wait_fence(obj);
+		if (ret)
+			return ret;
+	}
+
+	/* Just update our place in the LRU if our fence is getting reused. */
+	if (obj->fence_reg != I915_FENCE_REG_NONE) {
+		reg = &dev_priv->fence_regs[obj->fence_reg];
+		if (!obj->fence_dirty) {
+			list_move_tail(&reg->lru_list,
+				       &dev_priv->mm.fence_list);
+			return 0;
+		}
+	} else if (enable) {
+		if (WARN_ON(!obj->map_and_fenceable))
+			return -EINVAL;
+
+		reg = i915_find_fence_reg(dev);
+		if (IS_ERR(reg))
+			return PTR_ERR(reg);
+
+		if (reg->obj) {
+			struct drm_i915_gem_object *old = reg->obj;
+
+			ret = i915_gem_object_wait_fence(old);
+			if (ret)
+				return ret;
+
+			i915_gem_object_fence_lost(old);
+		}
+	} else
+		return 0;
+
+	i915_gem_object_update_fence(obj, reg, enable);
+
+	return 0;
+}
+
+bool
+i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
+{
+	if (obj->fence_reg != I915_FENCE_REG_NONE) {
+		struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+		struct i915_vma *ggtt_vma = i915_gem_obj_to_ggtt(obj);
+
+		WARN_ON(!ggtt_vma ||
+			dev_priv->fence_regs[obj->fence_reg].pin_count >
+			ggtt_vma->pin_count);
+		dev_priv->fence_regs[obj->fence_reg].pin_count++;
+		return true;
+	} else
+		return false;
+}
+
+void
+i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
+{
+	if (obj->fence_reg != I915_FENCE_REG_NONE) {
+		struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+		WARN_ON(dev_priv->fence_regs[obj->fence_reg].pin_count <= 0);
+		dev_priv->fence_regs[obj->fence_reg].pin_count--;
+	}
+}
+
+void i915_gem_restore_fences(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int i;
+
+	for (i = 0; i < dev_priv->num_fence_regs; i++) {
+		struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
+
+		/*
+		 * Commit delayed tiling changes if we have an object still
+		 * attached to the fence, otherwise just clear the fence.
+		 */
+		if (reg->obj) {
+			i915_gem_object_update_fence(reg->obj, reg,
+						     reg->obj->tiling_mode);
+		} else {
+			i915_gem_write_fence(dev, i, NULL);
+		}
+	}
+}
-- 
2.1.4

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Re: [PATCH 2/3] drm/i915: Extract i915_gem_fence.c

[Chris Wilson]

On Fri, Jul 24, 2015 at 01:55:11PM +0200, Daniel Vetter wrote:
> No code changes, just moving all the fence related code into a
> separate file (and avoiding a bunch of forward declarations while at
> it).

As well as i915_gem_tiling? i915_gem_fence is a better name, so can we
move the tiling ioctl to i915_gem_fence.c as well?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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[PATCH 3/3] drm/i915: kerneldoc for fences

[Daniel Vetter]

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 Documentation/DocBook/drm.tmpl        |  5 +++
 drivers/gpu/drm/i915/i915_gem_fence.c | 75 +++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 458772e6ce08..86c9c453b218 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -4137,6 +4137,11 @@ int num_ioctls;</synopsis>
 !Idrivers/gpu/drm/i915/i915_gem_gtt.c
       </sect2>
       <sect2>
+        <title>Global GTT Fence Handling</title>
+!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence handling
+!Idrivers/gpu/drm/i915/i915_gem_fence.c
+      </sect2>
+      <sect2>
         <title>Buffer Object Eviction</title>
 	<para>
 	  This section documents the interface functions for evicting buffer
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index d3284ee04794..63d8d0d8a9cb 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -25,6 +25,36 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 
+/**
+ * DOC: fence handling
+ *
+ * Important to avoid confusions: "fences" in the i915 driver are not execution
+ * fences used to track command completion but hardware detiler objects which
+ * wrap a given range of the global GTT. Each platform has only a fairly limited
+ * set of these objects.
+ *
+ * Fences are used to detile GTT memory mappings. They're also connected to the
+ * hardware frontbuffer render tracking and hence interract with frontbuffer
+ * conmpression. Furthermore on older platforms fences are required for tiled
+ * objects used by the display engine. They can also be used by the render
+ * engine - they're required for blitter commands and are optional for render
+ * commands. But on gen4+ both display (with the exception of fbc) and rendering
+ * have their own tiling state bits and don't need fences.
+ *
+ * Also note that fences only support X and Y tiling and hence can't be used for
+ * the fancier new tiling formats like W, Ys and Yf.
+ *
+ * Finally note that because fences are such a restricted resource they're
+ * dynamically associated with objects. Furthermore fence state is committed to
+ * the hardware lazily to avoid unecessary stalls on gen2/3. Therefore code must
+ * explictly call i915_gem_object_get_fence() to synchronize fencing status
+ * for cpu access. Also note that some code wants an unfenced view, for those
+ * cases the fence can be removed forcefully with i915_gem_object_put_fence().
+ *
+ * Internally these functions will synchronize with userspace access by removing
+ * ptes as needed.
+ */
+
 static void i965_write_fence_reg(struct drm_device *dev, int reg,
 				 struct drm_i915_gem_object *obj)
 {
@@ -247,6 +277,17 @@ i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+/**
+ * i915_gem_object_put_fence - force-remove fence for an object
+ * @obj: object to map through a fence reg
+ *
+ * This function force-removes any fence from the given object, which is useful
+ * if the kernel wants to do untiled GTT access.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
 int
 i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
 {
@@ -322,6 +363,10 @@ deadlock:
  * and tiling format.
  *
  * For an untiled surface, this removes any existing fence.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
  */
 int
 i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
@@ -374,6 +419,21 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+/**
+ * i915_gem_object_pin_fence - pin fencing state
+ * @obj: object to pin fencing for
+ *
+ * This pins the fencing state (whether tiled or untiled) to make sure the
+ * object is ready to be used as a scanout target. Fencing status must be
+ * synchronize first by calling i915_gem_object_get_fence():
+ *
+ * The resulting fence pin reference must be released again with
+ * i915_gem_object_unpin_fence().
+ *
+ * Returns:
+ *
+ * True if the object has a fence, false otherwise.
+ */
 bool
 i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
 {
@@ -390,6 +450,14 @@ i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
 		return false;
 }
 
+/**
+ * i915_gem_object_unpin_fence - unpin fencing state
+ * @obj: object to unpin fencing for
+ *
+ * This releases the fence pin reference acquired through
+ * i915_gem_object_pin_fence. It will handle both objects with and without an
+ * attached fence correctly, callers do not need to distinguish this.
+ */
 void
 i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 {
@@ -400,6 +468,13 @@ i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 	}
 }
 
+/**
+ * i915_gem_restore_fences - restore fence state
+ * @dev: DRM device
+ *
+ * Restore the hw fence state to match the software tracking again, to be called
+ * after a gpu reset and on resume.
+ */
 void i915_gem_restore_fences(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-- 
2.1.4

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Re: [PATCH 3/3] drm/i915: kerneldoc for fences

[Chris Wilson]

On Fri, Jul 24, 2015 at 01:55:12PM +0200, Daniel Vetter wrote:
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  Documentation/DocBook/drm.tmpl        |  5 +++
>  drivers/gpu/drm/i915/i915_gem_fence.c | 75 +++++++++++++++++++++++++++++++++++
>  2 files changed, 80 insertions(+)
> 
> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
> index 458772e6ce08..86c9c453b218 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -4137,6 +4137,11 @@ int num_ioctls;</synopsis>
>  !Idrivers/gpu/drm/i915/i915_gem_gtt.c
>        </sect2>
>        <sect2>
> +        <title>Global GTT Fence Handling</title>
> +!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence handling
> +!Idrivers/gpu/drm/i915/i915_gem_fence.c
> +      </sect2>
> +      <sect2>
>          <title>Buffer Object Eviction</title>
>  	<para>
>  	  This section documents the interface functions for evicting buffer
> diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
> index d3284ee04794..63d8d0d8a9cb 100644
> --- a/drivers/gpu/drm/i915/i915_gem_fence.c
> +++ b/drivers/gpu/drm/i915/i915_gem_fence.c
> @@ -25,6 +25,36 @@
>  #include <drm/i915_drm.h>
>  #include "i915_drv.h"
>  
> +/**
> + * DOC: fence handling

DOC: fence register handling

Might as well aim not to be ambiguous when you start out by pointing out
the confusion between the GTT detiling registers and dma-fence.

> + *
> + * Important to avoid confusions: "fences" in the i915 driver are not execution
> + * fences used to track command completion but hardware detiler objects which
> + * wrap a given range of the global GTT. Each platform has only a fairly limited
> + * set of these objects.

Hmm, good point. Maybe i915_gem_tiling was the better name after all!
Otoh, i915_gem_fence is better as it prevents us from wondering whether
this is suitable for Yf etc.

We really should emphasize that again in the set-tiling documentation -
that is not about declaring the tiling for the buffer per-se, but about
fence allocation.

> + *
> + * Fences are used to detile GTT memory mappings. They're also connected to the
> + * hardware frontbuffer render tracking and hence interract with frontbuffer
> + * conmpression. Furthermore on older platforms fences are required for tiled
> + * objects used by the display engine. They can also be used by the render
> + * engine - they're required for blitter commands and are optional for render
> + * commands. But on gen4+ both display (with the exception of fbc) and rendering
> + * have their own tiling state bits and don't need fences.
> + *
> + * Also note that fences only support X and Y tiling and hence can't be used for
> + * the fancier new tiling formats like W, Ys and Yf.
> + *
> + * Finally note that because fences are such a restricted resource they're
> + * dynamically associated with objects. Furthermore fence state is committed to
> + * the hardware lazily to avoid unecessary stalls on gen2/3. Therefore code must
> + * explictly call i915_gem_object_get_fence() to synchronize fencing status
> + * for cpu access. Also note that some code wants an unfenced view, for those
> + * cases the fence can be removed forcefully with i915_gem_object_put_fence().
> + *
> + * Internally these functions will synchronize with userspace access by removing
> + * ptes as needed.

Revoking CPU ptes into GTT mmaps.

Important when discussing PTEs to be clear when we don't mean the GTT
PTEs (which I think is the default for the driver).
-Chris

-- 
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[PATCH 1/4] drm/i915: kerneldoc for fences

[Daniel Vetter]

v2: Clarify that this is about fence _registers_. Also clarify that
the fence code revokes cpu ptes and not gtt ptes. Both suggested by
Chris.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 Documentation/DocBook/drm.tmpl        |  5 +++
 drivers/gpu/drm/i915/i915_gem_fence.c | 75 +++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 86680f074111..d7dc91b7e98c 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -4051,6 +4051,11 @@ int num_ioctls;</synopsis>
 !Idrivers/gpu/drm/i915/i915_gem_gtt.c
       </sect2>
       <sect2>
+        <title>Global GTT Fence Handling</title>
+!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence register handling
+!Idrivers/gpu/drm/i915/i915_gem_fence.c
+      </sect2>
+      <sect2>
         <title>Buffer Object Eviction</title>
 	<para>
 	  This section documents the interface functions for evicting buffer
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index d3284ee04794..0434c42d8c11 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -25,6 +25,36 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 
+/**
+ * DOC: fence register handling
+ *
+ * Important to avoid confusions: "fences" in the i915 driver are not execution
+ * fences used to track command completion but hardware detiler objects which
+ * wrap a given range of the global GTT. Each platform has only a fairly limited
+ * set of these objects.
+ *
+ * Fences are used to detile GTT memory mappings. They're also connected to the
+ * hardware frontbuffer render tracking and hence interract with frontbuffer
+ * conmpression. Furthermore on older platforms fences are required for tiled
+ * objects used by the display engine. They can also be used by the render
+ * engine - they're required for blitter commands and are optional for render
+ * commands. But on gen4+ both display (with the exception of fbc) and rendering
+ * have their own tiling state bits and don't need fences.
+ *
+ * Also note that fences only support X and Y tiling and hence can't be used for
+ * the fancier new tiling formats like W, Ys and Yf.
+ *
+ * Finally note that because fences are such a restricted resource they're
+ * dynamically associated with objects. Furthermore fence state is committed to
+ * the hardware lazily to avoid unecessary stalls on gen2/3. Therefore code must
+ * explictly call i915_gem_object_get_fence() to synchronize fencing status
+ * for cpu access. Also note that some code wants an unfenced view, for those
+ * cases the fence can be removed forcefully with i915_gem_object_put_fence().
+ *
+ * Internally these functions will synchronize with userspace access by removing
+ * CPU ptes into GTT mmaps (not the GTT ptes themselves) as needed.
+ */
+
 static void i965_write_fence_reg(struct drm_device *dev, int reg,
 				 struct drm_i915_gem_object *obj)
 {
@@ -247,6 +277,17 @@ i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+/**
+ * i915_gem_object_put_fence - force-remove fence for an object
+ * @obj: object to map through a fence reg
+ *
+ * This function force-removes any fence from the given object, which is useful
+ * if the kernel wants to do untiled GTT access.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
 int
 i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
 {
@@ -322,6 +363,10 @@ deadlock:
  * and tiling format.
  *
  * For an untiled surface, this removes any existing fence.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
  */
 int
 i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
@@ -374,6 +419,21 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+/**
+ * i915_gem_object_pin_fence - pin fencing state
+ * @obj: object to pin fencing for
+ *
+ * This pins the fencing state (whether tiled or untiled) to make sure the
+ * object is ready to be used as a scanout target. Fencing status must be
+ * synchronize first by calling i915_gem_object_get_fence():
+ *
+ * The resulting fence pin reference must be released again with
+ * i915_gem_object_unpin_fence().
+ *
+ * Returns:
+ *
+ * True if the object has a fence, false otherwise.
+ */
 bool
 i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
 {
@@ -390,6 +450,14 @@ i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
 		return false;
 }
 
+/**
+ * i915_gem_object_unpin_fence - unpin fencing state
+ * @obj: object to unpin fencing for
+ *
+ * This releases the fence pin reference acquired through
+ * i915_gem_object_pin_fence. It will handle both objects with and without an
+ * attached fence correctly, callers do not need to distinguish this.
+ */
 void
 i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 {
@@ -400,6 +468,13 @@ i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 	}
 }
 
+/**
+ * i915_gem_restore_fences - restore fence state
+ * @dev: DRM device
+ *
+ * Restore the hw fence state to match the software tracking again, to be called
+ * after a gpu reset and on resume.
+ */
 void i915_gem_restore_fences(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-- 
2.1.4

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[PATCH 2/4] drm/i915: Remove bogus kerneldoc include directive

[Daniel Vetter]

Afaict intel_irq_fini never existed. No idea how that one came
about.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 Documentation/DocBook/drm.tmpl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index d7dc91b7e98c..e56bc0d01fdd 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3920,7 +3920,6 @@ int num_ioctls;</synopsis>
         <title>Interrupt Handling</title>
 !Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling
 !Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init
-!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_fini
 !Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts
 !Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts
       </sect2>
-- 
2.1.4

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Re: [PATCH 2/4] drm/i915: Remove bogus kerneldoc include directive

[Chris Wilson]

On Fri, Jul 24, 2015 at 05:40:13PM +0200, Daniel Vetter wrote:
> Afaict intel_irq_fini never existed. No idea how that one came
> about.

It's notable by its absence. We should write it! There are a few steps
in intel_irq_init() that would be best undone intel_irq_fini(). The work
handlers could be dealt with by a comment that the core does a
flush_wq() - that at leasts says we have done due diligence and checked
that the work will be complete before module unload. But we should move
the pm_qos teardown here for instance.
-Chris

-- 
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[PATCH 3/4] drm/i915: Move low-level swizzling code to i915_gem_fence.c

[Daniel Vetter]

It fits more with the low-level fence code, and this move leaves only
the userspace tiling ioctl handling in i915_gem_tiling.c.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h        |   8 +-
 drivers/gpu/drm/i915/i915_gem_fence.c  | 268 +++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_tiling.c | 219 ---------------------------
 3 files changed, 272 insertions(+), 223 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4c34fb15d0df..9aebf92132a5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3058,6 +3058,10 @@ void i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj);
 
 void i915_gem_restore_fences(struct drm_device *dev);
 
+void i915_gem_detect_bit_6_swizzle(struct drm_device *dev);
+void i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj);
+void i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj);
+
 /* i915_gem_context.c */
 int __must_check i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
@@ -3150,10 +3154,6 @@ static inline bool i915_gem_object_needs_bit17_swizzle(struct drm_i915_gem_objec
 		obj->tiling_mode != I915_TILING_NONE;
 }
 
-void i915_gem_detect_bit_6_swizzle(struct drm_device *dev);
-void i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj);
-void i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj);
-
 /* i915_gem_debug.c */
 #if WATCH_LISTS
 int i915_verify_lists(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index 0434c42d8c11..c643260a90c5 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -495,3 +495,271 @@ void i915_gem_restore_fences(struct drm_device *dev)
 		}
 	}
 }
+
+/**
+ *
+ * Support for managing tiling state of buffer objects.
+ *
+ * The idea behind tiling is to increase cache hit rates by rearranging
+ * pixel data so that a group of pixel accesses are in the same cacheline.
+ * Performance improvement from doing this on the back/depth buffer are on
+ * the order of 30%.
+ *
+ * Intel architectures make this somewhat more complicated, though, by
+ * adjustments made to addressing of data when the memory is in interleaved
+ * mode (matched pairs of DIMMS) to improve memory bandwidth.
+ * For interleaved memory, the CPU sends every sequential 64 bytes
+ * to an alternate memory channel so it can get the bandwidth from both.
+ *
+ * The GPU also rearranges its accesses for increased bandwidth to interleaved
+ * memory, and it matches what the CPU does for non-tiled.  However, when tiled
+ * it does it a little differently, since one walks addresses not just in the
+ * X direction but also Y.  So, along with alternating channels when bit
+ * 6 of the address flips, it also alternates when other bits flip --  Bits 9
+ * (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
+ * are common to both the 915 and 965-class hardware.
+ *
+ * The CPU also sometimes XORs in higher bits as well, to improve
+ * bandwidth doing strided access like we do so frequently in graphics.  This
+ * is called "Channel XOR Randomization" in the MCH documentation.  The result
+ * is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
+ * decode.
+ *
+ * All of this bit 6 XORing has an effect on our memory management,
+ * as we need to make sure that the 3d driver can correctly address object
+ * contents.
+ *
+ * If we don't have interleaved memory, all tiling is safe and no swizzling is
+ * required.
+ *
+ * When bit 17 is XORed in, we simply refuse to tile at all.  Bit
+ * 17 is not just a page offset, so as we page an objet out and back in,
+ * individual pages in it will have different bit 17 addresses, resulting in
+ * each 64 bytes being swapped with its neighbor!
+ *
+ * Otherwise, if interleaved, we have to tell the 3d driver what the address
+ * swizzling it needs to do is, since it's writing with the CPU to the pages
+ * (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
+ * pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
+ * required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
+ * to match what the GPU expects.
+ */
+
+/**
+ * Detects bit 6 swizzling of address lookup between IGD access and CPU
+ * access through main memory.
+ */
+void
+i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
+	uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
+
+	if (INTEL_INFO(dev)->gen >= 8 || IS_VALLEYVIEW(dev)) {
+		/*
+		 * On BDW+, swizzling is not used. We leave the CPU memory
+		 * controller in charge of optimizing memory accesses without
+		 * the extra address manipulation GPU side.
+		 *
+		 * VLV and CHV don't have GPU swizzling.
+		 */
+		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+	} else if (INTEL_INFO(dev)->gen >= 6) {
+		if (dev_priv->preserve_bios_swizzle) {
+			if (I915_READ(DISP_ARB_CTL) &
+			    DISP_TILE_SURFACE_SWIZZLING) {
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else {
+				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+			}
+		} else {
+			uint32_t dimm_c0, dimm_c1;
+			dimm_c0 = I915_READ(MAD_DIMM_C0);
+			dimm_c1 = I915_READ(MAD_DIMM_C1);
+			dimm_c0 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
+			dimm_c1 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
+			/* Enable swizzling when the channels are populated
+			 * with identically sized dimms. We don't need to check
+			 * the 3rd channel because no cpu with gpu attached
+			 * ships in that configuration. Also, swizzling only
+			 * makes sense for 2 channels anyway. */
+			if (dimm_c0 == dimm_c1) {
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else {
+				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+			}
+		}
+	} else if (IS_GEN5(dev)) {
+		/* On Ironlake whatever DRAM config, GPU always do
+		 * same swizzling setup.
+		 */
+		swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+		swizzle_y = I915_BIT_6_SWIZZLE_9;
+	} else if (IS_GEN2(dev)) {
+		/* As far as we know, the 865 doesn't have these bit 6
+		 * swizzling issues.
+		 */
+		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+	} else if (IS_MOBILE(dev) || (IS_GEN3(dev) && !IS_G33(dev))) {
+		uint32_t dcc;
+
+		/* On 9xx chipsets, channel interleave by the CPU is
+		 * determined by DCC.  For single-channel, neither the CPU
+		 * nor the GPU do swizzling.  For dual channel interleaved,
+		 * the GPU's interleave is bit 9 and 10 for X tiled, and bit
+		 * 9 for Y tiled.  The CPU's interleave is independent, and
+		 * can be based on either bit 11 (haven't seen this yet) or
+		 * bit 17 (common).
+		 */
+		dcc = I915_READ(DCC);
+		switch (dcc & DCC_ADDRESSING_MODE_MASK) {
+		case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
+		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
+			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+			break;
+		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
+			if (dcc & DCC_CHANNEL_XOR_DISABLE) {
+				/* This is the base swizzling by the GPU for
+				 * tiled buffers.
+				 */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else if ((dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
+				/* Bit 11 swizzling by the CPU in addition. */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
+				swizzle_y = I915_BIT_6_SWIZZLE_9_11;
+			} else {
+				/* Bit 17 swizzling by the CPU in addition. */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10_17;
+				swizzle_y = I915_BIT_6_SWIZZLE_9_17;
+			}
+			break;
+		}
+
+		/* check for L-shaped memory aka modified enhanced addressing */
+		if (IS_GEN4(dev)) {
+			uint32_t ddc2 = I915_READ(DCC2);
+
+			if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE))
+				dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
+		}
+
+		if (dcc == 0xffffffff) {
+			DRM_ERROR("Couldn't read from MCHBAR.  "
+				  "Disabling tiling.\n");
+			swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
+			swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
+		}
+	} else {
+		/* The 965, G33, and newer, have a very flexible memory
+		 * configuration.  It will enable dual-channel mode
+		 * (interleaving) on as much memory as it can, and the GPU
+		 * will additionally sometimes enable different bit 6
+		 * swizzling for tiled objects from the CPU.
+		 *
+		 * Here's what I found on the G965:
+		 *    slot fill         memory size  swizzling
+		 * 0A   0B   1A   1B    1-ch   2-ch
+		 * 512  0    0    0     512    0     O
+		 * 512  0    512  0     16     1008  X
+		 * 512  0    0    512   16     1008  X
+		 * 0    512  0    512   16     1008  X
+		 * 1024 1024 1024 0     2048   1024  O
+		 *
+		 * We could probably detect this based on either the DRB
+		 * matching, which was the case for the swizzling required in
+		 * the table above, or from the 1-ch value being less than
+		 * the minimum size of a rank.
+		 */
+		if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) {
+			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+		} else {
+			swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+			swizzle_y = I915_BIT_6_SWIZZLE_9;
+		}
+	}
+
+	dev_priv->mm.bit_6_swizzle_x = swizzle_x;
+	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
+}
+
+/**
+ * Swap every 64 bytes of this page around, to account for it having a new
+ * bit 17 of its physical address and therefore being interpreted differently
+ * by the GPU.
+ */
+static void
+i915_gem_swizzle_page(struct page *page)
+{
+	char temp[64];
+	char *vaddr;
+	int i;
+
+	vaddr = kmap(page);
+
+	for (i = 0; i < PAGE_SIZE; i += 128) {
+		memcpy(temp, &vaddr[i], 64);
+		memcpy(&vaddr[i], &vaddr[i + 64], 64);
+		memcpy(&vaddr[i + 64], temp, 64);
+	}
+
+	kunmap(page);
+}
+
+void
+i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
+{
+	struct sg_page_iter sg_iter;
+	int i;
+
+	if (obj->bit_17 == NULL)
+		return;
+
+	i = 0;
+	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
+		struct page *page = sg_page_iter_page(&sg_iter);
+		char new_bit_17 = page_to_phys(page) >> 17;
+		if ((new_bit_17 & 0x1) !=
+		    (test_bit(i, obj->bit_17) != 0)) {
+			i915_gem_swizzle_page(page);
+			set_page_dirty(page);
+		}
+		i++;
+	}
+}
+
+void
+i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
+{
+	struct sg_page_iter sg_iter;
+	int page_count = obj->base.size >> PAGE_SHIFT;
+	int i;
+
+	if (obj->bit_17 == NULL) {
+		obj->bit_17 = kcalloc(BITS_TO_LONGS(page_count),
+				      sizeof(long), GFP_KERNEL);
+		if (obj->bit_17 == NULL) {
+			DRM_ERROR("Failed to allocate memory for bit 17 "
+				  "record\n");
+			return;
+		}
+	}
+
+	i = 0;
+	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
+		if (page_to_phys(sg_page_iter_page(&sg_iter)) & (1 << 17))
+			__set_bit(i, obj->bit_17);
+		else
+			__clear_bit(i, obj->bit_17);
+		i++;
+	}
+}
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 633bd1fcab69..fa7a8d7a24e0 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -80,153 +80,6 @@
  * to match what the GPU expects.
  */
 
-/**
- * Detects bit 6 swizzling of address lookup between IGD access and CPU
- * access through main memory.
- */
-void
-i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
-	uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
-
-	if (INTEL_INFO(dev)->gen >= 8 || IS_VALLEYVIEW(dev)) {
-		/*
-		 * On BDW+, swizzling is not used. We leave the CPU memory
-		 * controller in charge of optimizing memory accesses without
-		 * the extra address manipulation GPU side.
-		 *
-		 * VLV and CHV don't have GPU swizzling.
-		 */
-		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-	} else if (INTEL_INFO(dev)->gen >= 6) {
-		if (dev_priv->preserve_bios_swizzle) {
-			if (I915_READ(DISP_ARB_CTL) &
-			    DISP_TILE_SURFACE_SWIZZLING) {
-				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
-				swizzle_y = I915_BIT_6_SWIZZLE_9;
-			} else {
-				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-			}
-		} else {
-			uint32_t dimm_c0, dimm_c1;
-			dimm_c0 = I915_READ(MAD_DIMM_C0);
-			dimm_c1 = I915_READ(MAD_DIMM_C1);
-			dimm_c0 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
-			dimm_c1 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
-			/* Enable swizzling when the channels are populated
-			 * with identically sized dimms. We don't need to check
-			 * the 3rd channel because no cpu with gpu attached
-			 * ships in that configuration. Also, swizzling only
-			 * makes sense for 2 channels anyway. */
-			if (dimm_c0 == dimm_c1) {
-				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
-				swizzle_y = I915_BIT_6_SWIZZLE_9;
-			} else {
-				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-			}
-		}
-	} else if (IS_GEN5(dev)) {
-		/* On Ironlake whatever DRAM config, GPU always do
-		 * same swizzling setup.
-		 */
-		swizzle_x = I915_BIT_6_SWIZZLE_9_10;
-		swizzle_y = I915_BIT_6_SWIZZLE_9;
-	} else if (IS_GEN2(dev)) {
-		/* As far as we know, the 865 doesn't have these bit 6
-		 * swizzling issues.
-		 */
-		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-	} else if (IS_MOBILE(dev) || (IS_GEN3(dev) && !IS_G33(dev))) {
-		uint32_t dcc;
-
-		/* On 9xx chipsets, channel interleave by the CPU is
-		 * determined by DCC.  For single-channel, neither the CPU
-		 * nor the GPU do swizzling.  For dual channel interleaved,
-		 * the GPU's interleave is bit 9 and 10 for X tiled, and bit
-		 * 9 for Y tiled.  The CPU's interleave is independent, and
-		 * can be based on either bit 11 (haven't seen this yet) or
-		 * bit 17 (common).
-		 */
-		dcc = I915_READ(DCC);
-		switch (dcc & DCC_ADDRESSING_MODE_MASK) {
-		case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
-		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
-			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-			break;
-		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
-			if (dcc & DCC_CHANNEL_XOR_DISABLE) {
-				/* This is the base swizzling by the GPU for
-				 * tiled buffers.
-				 */
-				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
-				swizzle_y = I915_BIT_6_SWIZZLE_9;
-			} else if ((dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
-				/* Bit 11 swizzling by the CPU in addition. */
-				swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
-				swizzle_y = I915_BIT_6_SWIZZLE_9_11;
-			} else {
-				/* Bit 17 swizzling by the CPU in addition. */
-				swizzle_x = I915_BIT_6_SWIZZLE_9_10_17;
-				swizzle_y = I915_BIT_6_SWIZZLE_9_17;
-			}
-			break;
-		}
-
-		/* check for L-shaped memory aka modified enhanced addressing */
-		if (IS_GEN4(dev)) {
-			uint32_t ddc2 = I915_READ(DCC2);
-
-			if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE))
-				dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
-		}
-
-		if (dcc == 0xffffffff) {
-			DRM_ERROR("Couldn't read from MCHBAR.  "
-				  "Disabling tiling.\n");
-			swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
-			swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
-		}
-	} else {
-		/* The 965, G33, and newer, have a very flexible memory
-		 * configuration.  It will enable dual-channel mode
-		 * (interleaving) on as much memory as it can, and the GPU
-		 * will additionally sometimes enable different bit 6
-		 * swizzling for tiled objects from the CPU.
-		 *
-		 * Here's what I found on the G965:
-		 *    slot fill         memory size  swizzling
-		 * 0A   0B   1A   1B    1-ch   2-ch
-		 * 512  0    0    0     512    0     O
-		 * 512  0    512  0     16     1008  X
-		 * 512  0    0    512   16     1008  X
-		 * 0    512  0    512   16     1008  X
-		 * 1024 1024 1024 0     2048   1024  O
-		 *
-		 * We could probably detect this based on either the DRB
-		 * matching, which was the case for the swizzling required in
-		 * the table above, or from the 1-ch value being less than
-		 * the minimum size of a rank.
-		 */
-		if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) {
-			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
-			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-		} else {
-			swizzle_x = I915_BIT_6_SWIZZLE_9_10;
-			swizzle_y = I915_BIT_6_SWIZZLE_9;
-		}
-	}
-
-	dev_priv->mm.bit_6_swizzle_x = swizzle_x;
-	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
-}
-
 /* Check pitch constriants for all chips & tiling formats */
 static bool
 i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
@@ -475,75 +328,3 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
 
 	return 0;
 }
-
-/**
- * Swap every 64 bytes of this page around, to account for it having a new
- * bit 17 of its physical address and therefore being interpreted differently
- * by the GPU.
- */
-static void
-i915_gem_swizzle_page(struct page *page)
-{
-	char temp[64];
-	char *vaddr;
-	int i;
-
-	vaddr = kmap(page);
-
-	for (i = 0; i < PAGE_SIZE; i += 128) {
-		memcpy(temp, &vaddr[i], 64);
-		memcpy(&vaddr[i], &vaddr[i + 64], 64);
-		memcpy(&vaddr[i + 64], temp, 64);
-	}
-
-	kunmap(page);
-}
-
-void
-i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
-{
-	struct sg_page_iter sg_iter;
-	int i;
-
-	if (obj->bit_17 == NULL)
-		return;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
-		struct page *page = sg_page_iter_page(&sg_iter);
-		char new_bit_17 = page_to_phys(page) >> 17;
-		if ((new_bit_17 & 0x1) !=
-		    (test_bit(i, obj->bit_17) != 0)) {
-			i915_gem_swizzle_page(page);
-			set_page_dirty(page);
-		}
-		i++;
-	}
-}
-
-void
-i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
-{
-	struct sg_page_iter sg_iter;
-	int page_count = obj->base.size >> PAGE_SHIFT;
-	int i;
-
-	if (obj->bit_17 == NULL) {
-		obj->bit_17 = kcalloc(BITS_TO_LONGS(page_count),
-				      sizeof(long), GFP_KERNEL);
-		if (obj->bit_17 == NULL) {
-			DRM_ERROR("Failed to allocate memory for bit 17 "
-				  "record\n");
-			return;
-		}
-	}
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
-		if (page_to_phys(sg_page_iter_page(&sg_iter)) & (1 << 17))
-			__set_bit(i, obj->bit_17);
-		else
-			__clear_bit(i, obj->bit_17);
-		i++;
-	}
-}
-- 
2.1.4

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[PATCH 4/4] drm/i915: kerneldoc for tiling IOCTL and swizzle functions

[Daniel Vetter]

Chris rightfully suggested that documenting fences without documenting
the BO tiling tracking doesn't make much sense, so fix that.

The important bit to stress here (since it lead to some confusion) is
the GEM doesn't really care about tiling. Except for a few select cases
where the kernel needs to manage something that userspace can't take
care of: Namely the limited number of fences and fixing up swizzling,
although we still fail at the later.

v2: Move the low-level tiling/swizzling functions and kerneldoc to
i915_gem_fence.c and leave only the userspace interface here.
Suggested by Chris.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 Documentation/DocBook/drm.tmpl         | 16 ++++++-
 drivers/gpu/drm/i915/i915_gem_fence.c  | 28 ++++++++++--
 drivers/gpu/drm/i915/i915_gem_tiling.c | 84 +++++++++++++++++-----------------
 3 files changed, 80 insertions(+), 48 deletions(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index e56bc0d01fdd..f1884038b90f 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -4050,9 +4050,21 @@ int num_ioctls;</synopsis>
 !Idrivers/gpu/drm/i915/i915_gem_gtt.c
       </sect2>
       <sect2>
-        <title>Global GTT Fence Handling</title>
-!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence register handling
+        <title>GTT Fences and Swizzling</title>
 !Idrivers/gpu/drm/i915/i915_gem_fence.c
+        <sect3>
+          <title>Global GTT Fence Handling</title>
+!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence register handling
+        </sect3>
+        <sect3>
+          <title>Hardware Tiling and Swizzling Details</title>
+!Pdrivers/gpu/drm/i915/i915_gem_fence.c tiling swizzling details
+        </sect3>
+      </sect2>
+      <sect2>
+        <title>Object Tiling IOCTLs</title>
+!Idrivers/gpu/drm/i915/i915_gem_tiling.c
+!Pdrivers/gpu/drm/i915/i915_gem_tiling.c buffer object tiling
       </sect2>
       <sect2>
         <title>Buffer Object Eviction</title>
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index c643260a90c5..af1f8c461060 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -497,8 +497,7 @@ void i915_gem_restore_fences(struct drm_device *dev)
 }
 
 /**
- *
- * Support for managing tiling state of buffer objects.
+ * DOC: tiling swizzling details
  *
  * The idea behind tiling is to increase cache hit rates by rearranging
  * pixel data so that a group of pixel accesses are in the same cacheline.
@@ -546,6 +545,9 @@ void i915_gem_restore_fences(struct drm_device *dev)
  */
 
 /**
+ * i915_gem_detect_bit_6_swizzle - detect bit 6 swizzling pattern
+ * @dev: DRM device
+ *
  * Detects bit 6 swizzling of address lookup between IGD access and CPU
  * access through main memory.
  */
@@ -692,7 +694,7 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
 }
 
-/**
+/*
  * Swap every 64 bytes of this page around, to account for it having a new
  * bit 17 of its physical address and therefore being interpreted differently
  * by the GPU.
@@ -715,6 +717,18 @@ i915_gem_swizzle_page(struct page *page)
 	kunmap(page);
 }
 
+/**
+ * i915_gem_object_do_bit_17_swizzle - fixup bit 17 swizzling
+ * @obj: i915 GEM buffer object
+ *
+ * This function fixes up the swizzling in case any page frame number for this
+ * object has changed in bit 17 since that state has been saved with
+ * i915_gem_object_save_bit_17_swizzle().
+ *
+ * This is called when pinning backing storage again, since the kernel is free
+ * to move unpinned backing storage around (either by directly moving pages or
+ * by swapping them out and back in again).
+ */
 void
 i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
 {
@@ -737,6 +751,14 @@ i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
 	}
 }
 
+/**
+ * i915_gem_object_save_bit_17_swizzle - save bit 17 swizzling
+ * @obj: i915 GEM buffer object
+ *
+ * This function saves the bit 17 of each page frame number so that swizzling
+ * can be fixed up later on with i915_gem_object_do_bit_17_swizzle(). This must
+ * be called before the backing storage can be unpinned.
+ */
 void
 i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index fa7a8d7a24e0..ac3eb566c9d2 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -31,53 +31,31 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 
-/** @file i915_gem_tiling.c
- *
- * Support for managing tiling state of buffer objects.
- *
- * The idea behind tiling is to increase cache hit rates by rearranging
- * pixel data so that a group of pixel accesses are in the same cacheline.
- * Performance improvement from doing this on the back/depth buffer are on
- * the order of 30%.
- *
- * Intel architectures make this somewhat more complicated, though, by
- * adjustments made to addressing of data when the memory is in interleaved
- * mode (matched pairs of DIMMS) to improve memory bandwidth.
- * For interleaved memory, the CPU sends every sequential 64 bytes
- * to an alternate memory channel so it can get the bandwidth from both.
- *
- * The GPU also rearranges its accesses for increased bandwidth to interleaved
- * memory, and it matches what the CPU does for non-tiled.  However, when tiled
- * it does it a little differently, since one walks addresses not just in the
- * X direction but also Y.  So, along with alternating channels when bit
- * 6 of the address flips, it also alternates when other bits flip --  Bits 9
- * (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
- * are common to both the 915 and 965-class hardware.
- *
- * The CPU also sometimes XORs in higher bits as well, to improve
- * bandwidth doing strided access like we do so frequently in graphics.  This
- * is called "Channel XOR Randomization" in the MCH documentation.  The result
- * is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
- * decode.
+/**
+ * DOC: buffer object tiling
  *
- * All of this bit 6 XORing has an effect on our memory management,
- * as we need to make sure that the 3d driver can correctly address object
- * contents.
+ * i915_gem_set_tiling() and i915_gem_get_tiling() is the userspace interface to
+ * declare fence register requirements.
  *
- * If we don't have interleaved memory, all tiling is safe and no swizzling is
- * required.
+ * In principle GEM doesn't care at all about the internal data layout of an
+ * object, and hence it also doesn't care about tiling or swizzling. There's two
+ * exceptions:
  *
- * When bit 17 is XORed in, we simply refuse to tile at all.  Bit
- * 17 is not just a page offset, so as we page an objet out and back in,
- * individual pages in it will have different bit 17 addresses, resulting in
- * each 64 bytes being swapped with its neighbor!
+ * - For X and Y tiling the hardware provides detilers for CPU access, so called
+ *   fences. Since there's only a limited amount of them the kernel must manage
+ *   these, and therefore userspace must tell the kernel the object tiling if it
+ *   wants to use fences for detiling.
+ * - On gen3 and gen4 platforms have a swizzling pattern for tiled objects which
+ *   depends upon the physical page frame number. When swapping such objects the
+ *   page frame number might change and the kernel must be able to fix this up
+ *   and hence now the tiling. Note that on a subset of platforms with
+ *   asymmetric memory channel population the swizzling pattern changes in an
+ *   unknown way, and for those the kernel simply forbids swapping completely.
  *
- * Otherwise, if interleaved, we have to tell the 3d driver what the address
- * swizzling it needs to do is, since it's writing with the CPU to the pages
- * (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
- * pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
- * required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
- * to match what the GPU expects.
+ * Since neither of this applies for new tiling layouts on modern platforms like
+ * W, Ys and Yf tiling GEM only allows object tiling to be set to X or Y tiled.
+ * Anything else can be handled in userspace entirely without the kernel's
+ * invovlement.
  */
 
 /* Check pitch constriants for all chips & tiling formats */
@@ -166,8 +144,18 @@ i915_gem_object_fence_ok(struct drm_i915_gem_object *obj, int tiling_mode)
 }
 
 /**
+ * i915_gem_set_tiling - IOCTL handler to set tiling mode
+ * @dev: DRM device
+ * @data: data pointer for the ioctl
+ * @file: DRM file for the ioctl call
+ *
  * Sets the tiling mode of an object, returning the required swizzling of
  * bit 6 of addresses in the object.
+ *
+ * Called by the user via ioctl.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
  */
 int
 i915_gem_set_tiling(struct drm_device *dev, void *data,
@@ -285,7 +273,17 @@ err:
 }
 
 /**
+ * i915_gem_get_tiling - IOCTL handler to get tiling mode
+ * @dev: DRM device
+ * @data: data pointer for the ioctl
+ * @file: DRM file for the ioctl call
+ *
  * Returns the current tiling mode and required bit 6 swizzling for the object.
+ *
+ * Called by the user via ioctl.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
  */
 int
 i915_gem_get_tiling(struct drm_device *dev, void *data,
-- 
2.1.4

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Re: [PATCH 1/4] drm/i915: kerneldoc for fences

[Chris Wilson]

On Fri, Jul 24, 2015 at 05:40:12PM +0200, Daniel Vetter wrote:
> v2: Clarify that this is about fence _registers_. Also clarify that
> the fence code revokes cpu ptes and not gtt ptes. Both suggested by
> Chris.
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Quibble over 2, but 1,3,4 are
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
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Re: [PATCH 1/4] drm/i915: kerneldoc for fences

[Daniel Vetter]

On Fri, Jul 24, 2015 at 04:52:03PM +0100, Chris Wilson wrote:
> On Fri, Jul 24, 2015 at 05:40:12PM +0200, Daniel Vetter wrote:
> > v2: Clarify that this is about fence _registers_. Also clarify that
> > the fence code revokes cpu ptes and not gtt ptes. Both suggested by
> > Chris.
> > 
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 
> Quibble over 2, but 1,3,4 are
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Well 2 is just to avoid ugly in the generated docs so pulled that in too.
Plus the 2 earlier patches (those with your irc-ack). Thanks for the
feedback.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 3/3] drm/i915: kerneldoc for fences

[shuang.he]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he@intel.com)
Task id: 6855
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
ILK                                  295/295              295/295
SNB                                  315/315              315/315
IVB                                  342/342              342/342
BYT                 -2              285/285              283/285
HSW                                  378/378              378/378
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*BYT  igt@gem_partial_pwrite_pread@reads      PASS(1)      FAIL(1)
*BYT  igt@gem_partial_pwrite_pread@reads-display      PASS(1)      FAIL(1)
Note: You need to pay more attention to line start with '*'
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