Re: [PATCH v3 3/7] drm/fb-helper: Add fb_deferred_io support

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Apr 27, 2016 at 08:16:32PM +0200, Noralf Trønnes wrote:
> This adds deferred io support to drm_fb_helper.
> The fbdev framebuffer changes are flushed using the callback
> (struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
> ensuring that it always runs in process context.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
> 
> Changes since v2:
> - FB_DEFERRED_IO is now always selected by DRM_KMS_FB_HELPER, ifdef removed
> - The drm_clip_rect utility functions are dropped, so open code it
> - docs: use & to denote structs
> 
> Changes since v1:
> - Use a dedicated worker to run the framebuffer flushing like qxl does
> - Add parameter descriptions to drm_fb_helper_deferred_io
> 
>  drivers/gpu/drm/Kconfig         |   1 +
>  drivers/gpu/drm/drm_fb_helper.c | 109 +++++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_fb_helper.h     |  15 ++++++
>  3 files changed, 124 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 9e4f2f1..8e6f34b 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -52,6 +52,7 @@ config DRM_KMS_FB_HELPER
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
>  	select FB_CFB_IMAGEBLIT
> +	select FB_DEFERRED_IO
>  	help
>  	  FBDEV helpers for KMS drivers.
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 855108e..5112b5d 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -48,6 +48,8 @@ MODULE_PARM_DESC(fbdev_emulation,
> 
>  static LIST_HEAD(kernel_fb_helper_list);
> 
> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);

Instead of this forward decl just inline the few setup commands into
drm_fb_helper_prepare.

> +
>  /**
>   * DOC: fbdev helpers
>   *
> @@ -84,6 +86,15 @@ static LIST_HEAD(kernel_fb_helper_list);
>   * and set up an initial configuration using the detected hardware, drivers
>   * should call drm_fb_helper_single_add_all_connectors() followed by
>   * drm_fb_helper_initial_config().
> + *
> + * If CONFIG_FB_DEFERRED_IO is enabled and &drm_framebuffer_funcs ->dirty is
> + * set, the drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit}
> + * functions will accumulate changes and schedule &fb_helper .dirty_work to run
> + * right away. This worker then calls the dirty() function ensuring that it
> + * will always run in process context since the fb_*() function could be
> + * running in atomic context. If drm_fb_helper_deferred_io() is used as the
> + * deferred_io callback it will also schedule dirty_work with the damage
> + * collected from the mmap page writes.
>   */
> 
>  /**
> @@ -650,6 +661,7 @@ 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);
> +	drm_fb_helper_dirty_init(helper);
>  	helper->funcs = funcs;
>  	helper->dev = dev;
>  }
> @@ -834,6 +846,82 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>  }
>  EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
> 
> +static void drm_fb_helper_dirty_work(struct work_struct *work)
> +{
> +	struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
> +						    dirty_work);
> +	struct drm_clip_rect *clip = &helper->dirty_clip;
> +	struct drm_clip_rect clip_copy;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&helper->dirty_lock, flags);
> +	clip_copy = *clip;
> +	clip->x1 = clip->y1 = ~0;
> +	clip->x2 = clip->y2 = 0;
> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
> +
> +	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
> +}
> +
> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
> +{
> +	spin_lock_init(&helper->dirty_lock);
> +	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
> +	helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
> +}
> +
> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
> +				u32 width, u32 height)
> +{
> +	struct drm_fb_helper *helper = info->par;
> +	struct drm_clip_rect *clip = &helper->dirty_clip;
> +	unsigned long flags;
> +
> +	if (!helper->fb->funcs->dirty)
> +		return;
> +
> +	spin_lock_irqsave(&helper->dirty_lock, flags);
> +	clip->x1 = min_t(u32, clip->x1, x);
> +	clip->y1 = min_t(u32, clip->y1, y);
> +	clip->x2 = max_t(u32, clip->x2, x + width);
> +	clip->y2 = max_t(u32, clip->y2, y + height);
> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
> +
> +	schedule_work(&helper->dirty_work);
> +}
> +
> +/**
> + * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
> + * @info: fb_info struct pointer
> + * @pagelist: list of dirty mmap framebuffer pages
> + *
> + * This function is used as the &fb_deferred_io ->deferred_io
> + * callback function for flushing the fbdev mmap writes.
> + */
> +void drm_fb_helper_deferred_io(struct fb_info *info,
> +			       struct list_head *pagelist)
> +{
> +	unsigned long start, end, min, max;
> +	struct page *page;
> +	u32 y1, y2;
> +
> +	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) {
> +		y1 = min / info->fix.line_length;
> +		y2 = min_t(u32, max / info->fix.line_length, info->var.yres);

Needs a DIV_ROUND_UP here I think.

Besides these two nits nothing else I've spotted.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>


> +		drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
> +	}
> +}
> +EXPORT_SYMBOL(drm_fb_helper_deferred_io);
> +
>  /**
>   * drm_fb_helper_sys_read - wrapper around fb_sys_read
>   * @info: fb_info struct pointer
> @@ -862,7 +950,14 @@ 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_dirty(info, 0, 0, info->var.xres,
> +				    info->var.yres);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_write);
> 
> @@ -877,6 +972,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
>  				const struct fb_fillrect *rect)
>  {
>  	sys_fillrect(info, rect);
> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
> +			    rect->width, rect->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
> 
> @@ -891,6 +988,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
>  				const struct fb_copyarea *area)
>  {
>  	sys_copyarea(info, area);
> +	drm_fb_helper_dirty(info, area->dx, area->dy,
> +			    area->width, area->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
> 
> @@ -905,6 +1004,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
>  				 const struct fb_image *image)
>  {
>  	sys_imageblit(info, image);
> +	drm_fb_helper_dirty(info, image->dx, image->dy,
> +			    image->width, image->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
> 
> @@ -919,6 +1020,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
>  				const struct fb_fillrect *rect)
>  {
>  	cfb_fillrect(info, rect);
> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
> +			    rect->width, rect->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);
> 
> @@ -933,6 +1036,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
>  				const struct fb_copyarea *area)
>  {
>  	cfb_copyarea(info, area);
> +	drm_fb_helper_dirty(info, area->dx, area->dy,
> +			    area->width, area->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);
> 
> @@ -947,6 +1052,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
>  				 const struct fb_image *image)
>  {
>  	cfb_imageblit(info, image);
> +	drm_fb_helper_dirty(info, image->dx, image->dy,
> +			    image->width, image->height);
>  }
>  EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);
> 
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 062723b..5b4aa35 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -172,6 +172,10 @@ 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
> + * @dirty_work: worker used to flush the framebuffer
>   *
>   * This is the main structure used by the fbdev helpers. Drivers supporting
>   * fbdev emulation should embedded this into their overall driver structure.
> @@ -189,6 +193,9 @@ struct drm_fb_helper {
>  	const struct drm_fb_helper_funcs *funcs;
>  	struct fb_info *fbdev;
>  	u32 pseudo_palette[17];
> +	struct drm_clip_rect dirty_clip;
> +	spinlock_t dirty_lock;
> +	struct work_struct dirty_work;
> 
>  	/**
>  	 * @kernel_fb_list:
> @@ -245,6 +252,9 @@ 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,
> @@ -368,6 +378,11 @@ 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
> 

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