drm/udl: make usage as a console safer

Okay you don't really want to use udl devices as your console, but if
you are unlucky enough to do so, you run into a lot of schedule while atomic
due to printk being called from all sorts of funky places. So check if we
are in an atomic context, and queue the damage for later, the next printk
should cause it to appear. This isn't ideal, but it is simple, and seems to
work okay in my testing here.

(dirty area idea came from xenfb)

fixes a bunch of sleeping while atomic issues running fbcon on udl devices.

Cc: [e-mail]
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/udl/udl_drv.h

···
 	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)

drivers/gpu/drm/udl/udl_fb.c

···
 	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;
···
 		}
 	}
 
-	start_cycles = get_cycles();
-
 	aligned_x = DL_ALIGN_DOWN(x, sizeof(unsigned long));
 	width = DL_ALIGN_UP(width + (x-aligned_x), sizeof(unsigned long));
 	x = aligned_x;
···
 	    (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);
 	if (!urb)
 		return 0;
 	cmd = urb->transfer_buffer;
 
-	for (i = y; i < y + height ; i++) {
+	for (i = y; i <= y2 ; 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,
-				     width * bpp,
+				     (x2 - x + 1) * bpp,
 				     &bytes_identical, &bytes_sent))
 			goto error;
 	}
···
 {
 	int ret;
 
+	spin_lock_init(&ufb->dirty_lock);
 	ufb->obj = obj;
 	ret = drm_framebuffer_init(dev, &ufb->base, &udlfb_funcs);
 	drm_helper_mode_fill_fb_struct(&ufb->base, mode_cmd);