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

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Apr 08, 2016 at 07:05:03PM +0200, Noralf Trønnes wrote:
> 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@tronnes.org>

For this one it'd be awesome to throw patches for qxl/udl on top to remove
their own hand-rolled implementations. Just to maximize the testing
coverage of this new code. Should be doable to set up a qxl virtual
machine quickly, but even without that we should be able to pull it in
(since it's mostly just about removing code from these two drivers).
-Daniel

> ---
>  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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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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