[RFC v2 1/8] drm/fb-helper: Add fb_deferred_io support

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This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
Accumulated fbdev framebuffer changes are signaled using the callback
(struct drm_framebuffer_funcs *)->dirty()

The drm_fb_helper_sys_*() functions will accumulate changes and
schedule fb_info.deferred_work _if_ fb_info.fbdefio is set.
This worker is used by the deferred io mmap code to signal that it
has been collecting page faults. The page faults and/or other changes
are then merged into a drm_clip_rect and passed to the framebuffer
dirty() function.

The driver is responsible for setting up the fb_info.fbdefio structure
and calling fb_deferred_io_init() using the provided callback:
(struct fb_info *)->fbdefio->deferred_io = drm_fb_helper_deferred_io;

Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
---
 drivers/gpu/drm/drm_fb_helper.c | 189 +++++++++++++++++++++++++++++++++++++++-
 include/drm/drm_fb_helper.h     |  15 ++++
 2 files changed, 203 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 1e103c4..30f3dfd 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -48,6 +48,100 @@ MODULE_PARM_DESC(fbdev_emulation,
 
 static LIST_HEAD(kernel_fb_helper_list);
 
+/*
+ * Where should I put these drm_clip_rect functions?
+ */
+
+/**
+ * drm_clip_rect_reset - Reset clip
+ * @clip: clip rectangle
+ *
+ * Sets clip to {0,0,0,0}.
+ */
+static inline void drm_clip_rect_reset(struct drm_clip_rect *clip)
+{
+	clip->x1 = 0;
+	clip->x2 = 0;
+	clip->y1 = 0;
+	clip->y2 = 0;
+}
+
+/**
+ * drm_clip_rect_is_empty - Is clip empty?
+ * @clip: clip rectangle
+ *
+ * Returns true if clip is {0,0,0,0}.
+ */
+static inline bool drm_clip_rect_is_empty(struct drm_clip_rect *clip)
+{
+	return (!clip->x1 && !clip->x2 && !clip->y1 && !clip->y2);
+}
+
+/**
+ * drm_clip_rect_sanetize - Make sure clip rectangle has sane values
+ * @clip: clip rectangle
+ * @width: maximum width of rectangle
+ * @height: maximum height of rectangle
+ *
+ * Makes sure the clip doesn't exceed the specified width and height and that
+ * x1 <= x2 and y1 <= y2.
+ */
+void drm_clip_rect_sanetize(struct drm_clip_rect *clip, u32 width, u32 height)
+{
+	if (clip->x1 > clip->x2)
+		swap(clip->x1, clip->x2);
+	if (clip->y1 > clip->y2)
+		swap(clip->y1, clip->y2);
+
+	clip->x1 = min_t(u32, clip->x1, width - 1);
+	clip->x2 = min_t(u32, clip->x2, width - 1);
+	clip->y1 = min_t(u32, clip->y1, height - 1);
+	clip->y2 = min_t(u32, clip->y2, height - 1);
+}
+EXPORT_SYMBOL(drm_clip_rect_sanetize);
+
+/**
+ * drm_clip_rect_merge - Merge clip rectangles
+ * @dst: destination clip rectangle
+ * @src: source clip rectangle(s), can be NULL
+ * @num_clips: number of source clip rectangles
+ * @width: width of rectangle if @src is NULL
+ * @height: height of rectangle if @src is NULL
+ *
+ * The dirtyfb ioctl allows for a NULL clip to be passed in,
+ * so if @src is NULL, width and height is used to set a full clip.
+ * @dst takes part in the merge unless it is empty {0,0,0,0}.
+ */
+void drm_clip_rect_merge(struct drm_clip_rect *dst,
+			 struct drm_clip_rect *src, unsigned num_clips,
+			 unsigned flags, u32 width, u32 height)
+{
+	int i;
+
+	if (!src || !num_clips) {
+		dst->x1 = 0;
+		dst->x2 = width - 1;
+		dst->y1 = 0;
+		dst->y2 = height - 1;
+		return;
+	}
+
+	if (drm_clip_rect_is_empty(dst)) {
+		dst->x1 = ~0;
+		dst->y1 = ~0;
+	}
+
+	for (i = 0; i < num_clips; i++) {
+		if (flags & DRM_MODE_FB_DIRTY_ANNOTATE_COPY)
+			i++;
+		dst->x1 = min(dst->x1, src[i].x1);
+		dst->x2 = max(dst->x2, src[i].x2);
+		dst->y1 = min(dst->y1, src[i].y1);
+		dst->y2 = max(dst->y2, src[i].y2);
+	}
+}
+EXPORT_SYMBOL(drm_clip_rect_merge);
+
 /**
  * DOC: fbdev helpers
  *
@@ -410,6 +504,13 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
 
 	drm_warn_on_modeset_not_all_locked(dev);
 
+#ifdef CONFIG_FB_DEFERRED_IO
+	spin_lock(&fb_helper->dirty_lock);
+	drm_clip_rect_merge(&fb_helper->dirty_clip, NULL, 0, 0,
+			    fb_helper->fbdev->var.xres,
+			    fb_helper->fbdev->var.yres);
+	spin_unlock(&fb_helper->dirty_lock);
+#endif
 	if (fb_helper->atomic)
 		return restore_fbdev_mode_atomic(fb_helper);
 
@@ -654,6 +755,9 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 			   const struct drm_fb_helper_funcs *funcs)
 {
 	INIT_LIST_HEAD(&helper->kernel_fb_list);
+#ifdef CONFIG_FB_DEFERRED_IO
+	spin_lock_init(&helper->dirty_lock);
+#endif
 	helper->funcs = funcs;
 	helper->dev = dev;
 }
@@ -838,6 +942,76 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 }
 EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
 
+#ifdef CONFIG_FB_DEFERRED_IO
+void drm_fb_helper_deferred_io(struct fb_info *info,
+			       struct list_head *pagelist)
+{
+	struct drm_fb_helper *helper = info->par;
+	unsigned long start, end, min, max;
+	struct drm_clip_rect clip;
+	struct page *page;
+
+	if (!helper->fb->funcs->dirty)
+		return;
+
+	spin_lock(&helper->dirty_lock);
+	clip = helper->dirty_clip;
+	drm_clip_rect_reset(&helper->dirty_clip);
+	spin_unlock(&helper->dirty_lock);
+
+	min = ULONG_MAX;
+	max = 0;
+	list_for_each_entry(page, pagelist, lru) {
+		start = page->index << PAGE_SHIFT;
+		end = start + PAGE_SIZE - 1;
+		min = min(min, start);
+		max = max(max, end);
+	}
+
+	if (min < max) {
+		clip.x1 = 0;
+		clip.x2 = info->var.xres - 1;
+		clip.y1 = min / info->fix.line_length;
+		clip.y2 = min_t(u32, max / info->fix.line_length,
+				    info->var.yres - 1);
+	} else if (drm_clip_rect_is_empty(&clip)) {
+		clip.x1 = 0;
+		clip.x2 = info->var.xres - 1;
+		clip.y1 = 0;
+		clip.y2 = info->var.yres - 1;
+	}
+
+	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
+}
+EXPORT_SYMBOL(drm_fb_helper_deferred_io);
+
+static void drm_fb_helper_sys_deferred(struct fb_info *info, u32 x, u32 y,
+				       u32 width, u32 height)
+{
+	struct drm_fb_helper *helper = info->par;
+	struct drm_clip_rect clip;
+
+	if (!info->fbdefio)
+		return;
+
+	clip.x1 = x;
+	clip.x2 = x + width - 1;
+	clip.y1 = y;
+	clip.y2 = y + height - 1;
+
+	spin_lock(&helper->dirty_lock);
+	drm_clip_rect_merge(&helper->dirty_clip, &clip, 1, 0, 0, 0);
+	spin_unlock(&helper->dirty_lock);
+
+	schedule_delayed_work(&info->deferred_work, info->fbdefio->delay);
+}
+#else
+static inline void drm_fb_helper_sys_deferred(struct fb_info *info, u32 x, u32 y,
+					      u32 width, u32 height)
+{
+}
+#endif
+
 /**
  * drm_fb_helper_sys_read - wrapper around fb_sys_read
  * @info: fb_info struct pointer
@@ -866,7 +1040,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
-	return fb_sys_write(info, buf, count, ppos);
+	ssize_t ret;
+
+	ret = fb_sys_write(info, buf, count, ppos);
+	if (ret > 0)
+		drm_fb_helper_sys_deferred(info, 0, 0,
+					   info->var.xres, info->var.yres);
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_write);
 
@@ -881,6 +1062,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect)
 {
 	sys_fillrect(info, rect);
+	drm_fb_helper_sys_deferred(info, rect->dx, rect->dy,
+				   rect->width, rect->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
 
@@ -895,6 +1078,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
 				const struct fb_copyarea *area)
 {
 	sys_copyarea(info, area);
+	drm_fb_helper_sys_deferred(info, area->dx, area->dy,
+				   area->width, area->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
 
@@ -909,6 +1094,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
 				 const struct fb_image *image)
 {
 	sys_imageblit(info, image);
+	drm_fb_helper_sys_deferred(info, image->dx, image->dy,
+				   image->width, image->height);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
 
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index d8a40df..1daadc7 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -172,6 +172,9 @@ struct drm_fb_helper_connector {
  * @funcs: driver callbacks for fb helper
  * @fbdev: emulated fbdev device info struct
  * @pseudo_palette: fake palette of 16 colors
+ * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
+ *              the screen buffer
+ * @dirty_lock: spinlock protecting @dirty_clip
  *
  * This is the main structure used by the fbdev helpers. Drivers supporting
  * fbdev emulation should embedded this into their overall driver structure.
@@ -189,6 +192,10 @@ struct drm_fb_helper {
 	const struct drm_fb_helper_funcs *funcs;
 	struct fb_info *fbdev;
 	u32 pseudo_palette[17];
+#ifdef CONFIG_FB_DEFERRED_IO
+	struct drm_clip_rect dirty_clip;
+	spinlock_t dirty_lock;
+#endif
 
 	/**
 	 * @kernel_fb_list:
@@ -244,6 +251,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
 
 void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);
 
+void drm_fb_helper_deferred_io(struct fb_info *info,
+			       struct list_head *pagelist);
+
 ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos);
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
@@ -362,6 +372,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 {
 }
 
+static inline void drm_fb_helper_deferred_io(struct fb_info *info,
+					     struct list_head *pagelist)
+{
+}
+
 static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
 					     char __user *buf, size_t count,
 					     loff_t *ppos)
-- 
2.2.2

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