Date:	Wed, 20 Apr 2016 19:59:03 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Noralf Trønnes <noralf@...nnes.org>
Cc:	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	daniel@...ll.ch, laurent.pinchart@...asonboard.com,
	tomi.valkeinen@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] drm/udl: Use drm_fb_helper deferred_io support

On Wed, Apr 20, 2016 at 05:25:29PM +0200, Noralf Trønnes wrote:
> Use the fbdev deferred io support in drm_fb_helper.
> The (struct fb_ops *)->fb_{fillrect,copyarea,imageblit} functions will
> now be deferred in the same way that mmap damage is, instead of being
> flushed directly.
> The deferred mmap functionality is kept disabled by default, because of the
> list corruption problems mentioned in commit 677d23b70bf9
> ("drm/udl: disable fb_defio by default").
> This patch has only been compile tested.
> 
> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> ---
>  drivers/gpu/drm/udl/udl_drv.h |   2 -
>  drivers/gpu/drm/udl/udl_fb.c  | 152 ++++--------------------------------------
>  2 files changed, 12 insertions(+), 142 deletions(-)
> 
> diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
> index 4a064ef..0b03d34 100644
> --- a/drivers/gpu/drm/udl/udl_drv.h
> +++ b/drivers/gpu/drm/udl/udl_drv.h
> @@ -81,8 +81,6 @@ struct udl_framebuffer {
>  	struct drm_framebuffer base;
>  	struct udl_gem_object *obj;
>  	bool active_16; /* active on the 16-bit channel */
> -	int x1, y1, x2, y2; /* dirty rect */
> -	spinlock_t dirty_lock;
>  };
>  
>  #define to_udl_fb(x) container_of(x, struct udl_framebuffer, base)
> diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
> index a52de2f..b44d4a7 100644
> --- a/drivers/gpu/drm/udl/udl_fb.c
> +++ b/drivers/gpu/drm/udl/udl_fb.c
> @@ -77,68 +77,6 @@ static uint16_t rgb16(uint32_t col)
>  }
>  #endif
>  
> -/*
> - * NOTE: fb_defio.c is holding info->fbdefio.mutex
> - *   Touching ANY framebuffer memory that triggers a page fault
> - *   in fb_defio will cause a deadlock, when it also tries to
> - *   grab the same mutex.
> - */
> -static void udlfb_dpy_deferred_io(struct fb_info *info,
> -				  struct list_head *pagelist)
> -{
> -	struct page *cur;
> -	struct fb_deferred_io *fbdefio = info->fbdefio;
> -	struct udl_fbdev *ufbdev = info->par;
> -	struct drm_device *dev = ufbdev->ufb.base.dev;
> -	struct udl_device *udl = dev->dev_private;
> -	struct urb *urb;
> -	char *cmd;
> -	cycles_t start_cycles, end_cycles;
> -	int bytes_sent = 0;
> -	int bytes_identical = 0;
> -	int bytes_rendered = 0;
> -
> -	if (!fb_defio)
> -		return;
> -
> -	start_cycles = get_cycles();
> -
> -	urb = udl_get_urb(dev);
> -	if (!urb)
> -		return;
> -
> -	cmd = urb->transfer_buffer;
> -
> -	/* walk the written page list and render each to device */
> -	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
> -
> -		if (udl_render_hline(dev, (ufbdev->ufb.base.bits_per_pixel / 8),
> -				     &urb, (char *) info->fix.smem_start,
> -				     &cmd, cur->index << PAGE_SHIFT,
> -				     cur->index << PAGE_SHIFT,
> -				     PAGE_SIZE, &bytes_identical, &bytes_sent))
> -			goto error;
> -		bytes_rendered += PAGE_SIZE;
> -	}
> -
> -	if (cmd > (char *) urb->transfer_buffer) {
> -		/* Send partial buffer remaining before exiting */
> -		int len = cmd - (char *) urb->transfer_buffer;
> -		udl_submit_urb(dev, urb, len);
> -		bytes_sent += len;
> -	} else
> -		udl_urb_completion(urb);
> -
> -error:
> -	atomic_add(bytes_sent, &udl->bytes_sent);
> -	atomic_add(bytes_identical, &udl->bytes_identical);
> -	atomic_add(bytes_rendered, &udl->bytes_rendered);
> -	end_cycles = get_cycles();
> -	atomic_add(((unsigned int) ((end_cycles - start_cycles)
> -		    >> 10)), /* Kcycles */
> -		   &udl->cpu_kcycles_used);
> -}
> -
>  int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
>  		      int width, int height)
>  {
> @@ -152,9 +90,6 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
>  	struct urb *urb;
>  	int aligned_x;
>  	int bpp = (fb->base.bits_per_pixel / 8);
> -	int x2, y2;
> -	bool store_for_later = false;
> -	unsigned long flags;
>  
>  	if (!fb->active_16)
>  		return 0;
> @@ -180,38 +115,6 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
>  	    (y + height > fb->base.height))
>  		return -EINVAL;
>  
> -	/* if we are in atomic just store the info
> -	   can't test inside spin lock */
> -	if (in_atomic())
> -		store_for_later = true;
> -
> -	x2 = x + width - 1;
> -	y2 = y + height - 1;
> -
> -	spin_lock_irqsave(&fb->dirty_lock, flags);
> -
> -	if (fb->y1 < y)
> -		y = fb->y1;
> -	if (fb->y2 > y2)
> -		y2 = fb->y2;
> -	if (fb->x1 < x)
> -		x = fb->x1;
> -	if (fb->x2 > x2)
> -		x2 = fb->x2;
> -
> -	if (store_for_later) {
> -		fb->x1 = x;
> -		fb->x2 = x2;
> -		fb->y1 = y;
> -		fb->y2 = y2;
> -		spin_unlock_irqrestore(&fb->dirty_lock, flags);
> -		return 0;
> -	}
> -
> -	fb->x1 = fb->y1 = INT_MAX;
> -	fb->x2 = fb->y2 = 0;
> -
> -	spin_unlock_irqrestore(&fb->dirty_lock, flags);
>  	start_cycles = get_cycles();
>  
>  	urb = udl_get_urb(dev);
> @@ -219,14 +122,14 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
>  		return 0;
>  	cmd = urb->transfer_buffer;
>  
> -	for (i = y; i <= y2 ; i++) {
> +	for (i = y; i < height ; i++) {
>  		const int line_offset = fb->base.pitches[0] * i;
>  		const int byte_offset = line_offset + (x * bpp);
>  		const int dev_byte_offset = (fb->base.width * bpp * i) + (x * bpp);
>  		if (udl_render_hline(dev, bpp, &urb,
>  				     (char *) fb->obj->vmapping,
>  				     &cmd, byte_offset, dev_byte_offset,
> -				     (x2 - x + 1) * bpp,
> +				     width * bpp,
>  				     &bytes_identical, &bytes_sent))
>  			goto error;
>  	}
> @@ -283,36 +186,6 @@ static int udl_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  	return 0;
>  }
>  
> -static void udl_fb_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
> -{
> -	struct udl_fbdev *ufbdev = info->par;
> -
> -	sys_fillrect(info, rect);
> -
> -	udl_handle_damage(&ufbdev->ufb, rect->dx, rect->dy, rect->width,
> -			  rect->height);
> -}
> -
> -static void udl_fb_copyarea(struct fb_info *info, const struct fb_copyarea *region)
> -{
> -	struct udl_fbdev *ufbdev = info->par;
> -
> -	sys_copyarea(info, region);
> -
> -	udl_handle_damage(&ufbdev->ufb, region->dx, region->dy, region->width,
> -			  region->height);
> -}
> -
> -static void udl_fb_imageblit(struct fb_info *info, const struct fb_image *image)
> -{
> -	struct udl_fbdev *ufbdev = info->par;
> -
> -	sys_imageblit(info, image);
> -
> -	udl_handle_damage(&ufbdev->ufb, image->dx, image->dy, image->width,
> -			  image->height);
> -}
> -
>  /*
>   * It's common for several clients to have framebuffer open simultaneously.
>   * e.g. both fbcon and X. Makes things interesting.
> @@ -330,20 +203,20 @@ static int udl_fb_open(struct fb_info *info, int user)
>  
>  	ufbdev->fb_count++;
>  
> -	if (fb_defio && (info->fbdefio == NULL)) {
> -		/* enable defio at last moment if not disabled by client */
> +	if (!info->fbdefio) {
> +		/* enable defio at last moment */
>  
>  		struct fb_deferred_io *fbdefio;
>  
>  		fbdefio = kmalloc(sizeof(struct fb_deferred_io), GFP_KERNEL);
> -
>  		if (fbdefio) {
>  			fbdefio->delay = DL_DEFIO_WRITE_DELAY;
> -			fbdefio->deferred_io = udlfb_dpy_deferred_io;
> +			fbdefio->deferred_io = drm_fb_helper_deferred_io;

Why all these changes here? I figured just exchanging the deferred_io
pointer should be all that's really needed in the setup code?
-Daniel

> +			info->fbdefio = fbdefio;
> +			fb_deferred_io_init(info);
> +			if (!fb_defio) /* see commit 677d23b */
> +				info->fbops->fb_mmap = udl_fb_mmap;
>  		}
> -
> -		info->fbdefio = fbdefio;
> -		fb_deferred_io_init(info);
>  	}
>  
>  	pr_notice("open /dev/fb%d user=%d fb_info=%p count=%d\n",
> @@ -379,9 +252,9 @@ static struct fb_ops udlfb_ops = {
>  	.owner = THIS_MODULE,
>  	.fb_check_var = drm_fb_helper_check_var,
>  	.fb_set_par = drm_fb_helper_set_par,
> -	.fb_fillrect = udl_fb_fillrect,
> -	.fb_copyarea = udl_fb_copyarea,
> -	.fb_imageblit = udl_fb_imageblit,
> +	.fb_fillrect = drm_fb_helper_sys_fillrect,
> +	.fb_copyarea = drm_fb_helper_sys_copyarea,
> +	.fb_imageblit = drm_fb_helper_sys_imageblit,
>  	.fb_pan_display = drm_fb_helper_pan_display,
>  	.fb_blank = drm_fb_helper_blank,
>  	.fb_setcmap = drm_fb_helper_setcmap,
> @@ -458,7 +331,6 @@ udl_framebuffer_init(struct drm_device *dev,
>  {
>  	int ret;
>  
> -	spin_lock_init(&ufb->dirty_lock);
>  	ufb->obj = obj;
>  	drm_helper_mode_fill_fb_struct(&ufb->base, mode_cmd);
>  	ret = drm_framebuffer_init(dev, &ufb->base, &udlfb_funcs);
> -- 
> 2.2.2
> 

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

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