drm/qxl: add delayed fb operations

Due to the nature of qxl hw we cannot queue operations while in an irq
context, so we queue these operations as best we can until atomic allocations
fail, and dequeue them later in a work queue.

Daniel looked over the locking on the list and agrees it should be sufficent.

The atomic allocs use no warn, as the last thing we want if we haven't memory
to allocate space for a printk in an irq context is more printks.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/qxl/qxl_drv.h

@@ -314,6 +314,7 @@ struct qxl_device {
 	struct workqueue_struct *gc_queue;
 	struct work_struct gc_work;
 
+	struct work_struct fb_work;
 };
 
 /* forward declaration for QXL_INFO_IO */

drivers/gpu/drm/qxl/qxl_fb.c

@@ -37,12 +37,29 @@
 
 #define QXL_DIRTY_DELAY (HZ / 30)
 
+#define QXL_FB_OP_FILLRECT 1
+#define QXL_FB_OP_COPYAREA 2
+#define QXL_FB_OP_IMAGEBLIT 3
+
+struct qxl_fb_op {
+	struct list_head head;
+	int op_type;
+	union {
+		struct fb_fillrect fr;
+		struct fb_copyarea ca;
+		struct fb_image ib;
+	} op;
+	void *img_data;
+};
+
 struct qxl_fbdev {
 	struct drm_fb_helper helper;
 	struct qxl_framebuffer	qfb;
 	struct list_head	fbdev_list;
 	struct qxl_device	*qdev;
 
+	spinlock_t delayed_ops_lock;
+	struct list_head delayed_ops;
 	void *shadow;
 	int size;
 
@@ -164,8 +181,69 @@ static struct fb_deferred_io qxl_defio = {
 	.deferred_io	= qxl_deferred_io,
 };
 
-static void qxl_fb_fillrect(struct fb_info *info,
-			    const struct fb_fillrect *fb_rect)
+static void qxl_fb_delayed_fillrect(struct qxl_fbdev *qfbdev,
+				    const struct fb_fillrect *fb_rect)
+{
+	struct qxl_fb_op *op;
+	unsigned long flags;
+
+	op = kmalloc(sizeof(struct qxl_fb_op), GFP_ATOMIC | __GFP_NOWARN);
+	if (!op)
+		return;
+
+	op->op.fr = *fb_rect;
+	op->img_data = NULL;
+	op->op_type = QXL_FB_OP_FILLRECT;
+
+	spin_lock_irqsave(&qfbdev->delayed_ops_lock, flags);
+	list_add_tail(&op->head, &qfbdev->delayed_ops);
+	spin_unlock_irqrestore(&qfbdev->delayed_ops_lock, flags);
+}
+
+static void qxl_fb_delayed_copyarea(struct qxl_fbdev *qfbdev,
+				    const struct fb_copyarea *fb_copy)
+{
+	struct qxl_fb_op *op;
+	unsigned long flags;
+
+	op = kmalloc(sizeof(struct qxl_fb_op), GFP_ATOMIC | __GFP_NOWARN);
+	if (!op)
+		return;
+
+	op->op.ca = *fb_copy;
+	op->img_data = NULL;
+	op->op_type = QXL_FB_OP_COPYAREA;
+
+	spin_lock_irqsave(&qfbdev->delayed_ops_lock, flags);
+	list_add_tail(&op->head, &qfbdev->delayed_ops);
+	spin_unlock_irqrestore(&qfbdev->delayed_ops_lock, flags);
+}
+
+static void qxl_fb_delayed_imageblit(struct qxl_fbdev *qfbdev,
+				     const struct fb_image *fb_image)
+{
+	struct qxl_fb_op *op;
+	unsigned long flags;
+	uint32_t size = fb_image->width * fb_image->height * (fb_image->depth >= 8 ? fb_image->depth / 8 : 1);
+
+	op = kmalloc(sizeof(struct qxl_fb_op) + size, GFP_ATOMIC | __GFP_NOWARN);
+	if (!op)
+		return;
+
+	op->op.ib = *fb_image;
+	op->img_data = (void *)(op + 1);
+	op->op_type = QXL_FB_OP_IMAGEBLIT;
+
+	memcpy(op->img_data, fb_image->data, size);
+
+	op->op.ib.data = op->img_data;
+	spin_lock_irqsave(&qfbdev->delayed_ops_lock, flags);
+	list_add_tail(&op->head, &qfbdev->delayed_ops);
+	spin_unlock_irqrestore(&qfbdev->delayed_ops_lock, flags);
+}
+
+static void qxl_fb_fillrect_internal(struct fb_info *info,
+				     const struct fb_fillrect *fb_rect)
 {
 	struct qxl_fbdev *qfbdev = info->par;
 	struct qxl_device *qdev = qfbdev->qdev;
@@ -203,17 +281,28 @@ static void qxl_fb_fillrect(struct fb_info *info,
 	qxl_draw_fill_rec.rect = rect;
 	qxl_draw_fill_rec.color = color;
 	qxl_draw_fill_rec.rop = rop;
+
+	qxl_draw_fill(&qxl_draw_fill_rec);
+}
+
+static void qxl_fb_fillrect(struct fb_info *info,
+			    const struct fb_fillrect *fb_rect)
+{
+	struct qxl_fbdev *qfbdev = info->par;
+	struct qxl_device *qdev = qfbdev->qdev;
+
 	if (!drm_can_sleep()) {
-		qxl_io_log(qdev,
-			"%s: TODO use RCU, mysterious locks with spin_lock\n",
-			__func__);
+		qxl_fb_delayed_fillrect(qfbdev, fb_rect);
+		schedule_work(&qdev->fb_work);
 		return;
 	}
-	qxl_draw_fill(&qxl_draw_fill_rec);
+	/* make sure any previous work is done */
+	flush_work(&qdev->fb_work);
+	qxl_fb_fillrect_internal(info, fb_rect);
 }
 
-static void qxl_fb_copyarea(struct fb_info *info,
-			    const struct fb_copyarea *region)
+static void qxl_fb_copyarea_internal(struct fb_info *info,
+				     const struct fb_copyarea *region)
 {
 	struct qxl_fbdev *qfbdev = info->par;
 
@@ -223,37 +312,89 @@ static void qxl_fb_copyarea(struct fb_info *info,
 			  region->dx, region->dy);
 }
 
+static void qxl_fb_copyarea(struct fb_info *info,
+			    const struct fb_copyarea *region)
+{
+	struct qxl_fbdev *qfbdev = info->par;
+	struct qxl_device *qdev = qfbdev->qdev;
+
+	if (!drm_can_sleep()) {
+		qxl_fb_delayed_copyarea(qfbdev, region);
+		schedule_work(&qdev->fb_work);
+		return;
+	}
+	/* make sure any previous work is done */
+	flush_work(&qdev->fb_work);
+	qxl_fb_copyarea_internal(info, region);
+}
+
 static void qxl_fb_imageblit_safe(struct qxl_fb_image *qxl_fb_image)
 {
 	qxl_draw_opaque_fb(qxl_fb_image, 0);
 }
 
+static void qxl_fb_imageblit_internal(struct fb_info *info,
+				      const struct fb_image *image)
+{
+	struct qxl_fbdev *qfbdev = info->par;
+	struct qxl_fb_image qxl_fb_image;
+
+	/* ensure proper order  rendering operations - TODO: must do this
+	 * for everything. */
+	qxl_fb_image_init(&qxl_fb_image, qfbdev->qdev, info, image);
+	qxl_fb_imageblit_safe(&qxl_fb_image);
+}
+
 static void qxl_fb_imageblit(struct fb_info *info,
 			     const struct fb_image *image)
 {
 	struct qxl_fbdev *qfbdev = info->par;
 	struct qxl_device *qdev = qfbdev->qdev;
-	struct qxl_fb_image qxl_fb_image;
 
 	if (!drm_can_sleep()) {
-		/* we cannot do any ttm_bo allocation since that will fail on
-		 * ioremap_wc..__get_vm_area_node, so queue the work item
-		 * instead This can happen from printk inside an interrupt
-		 * context, i.e.: smp_apic_timer_interrupt..check_cpu_stall */
-		qxl_io_log(qdev,
-			"%s: TODO use RCU, mysterious locks with spin_lock\n",
-			   __func__);
+		qxl_fb_delayed_imageblit(qfbdev, image);
+		schedule_work(&qdev->fb_work);
 		return;
 	}
+	/* make sure any previous work is done */
+	flush_work(&qdev->fb_work);
+	qxl_fb_imageblit_internal(info, image);
+}
 
-	/* ensure proper order of rendering operations - TODO: must do this
-	 * for everything. */
-	qxl_fb_image_init(&qxl_fb_image, qfbdev->qdev, info, image);
-	qxl_fb_imageblit_safe(&qxl_fb_image);
+static void qxl_fb_work(struct work_struct *work)
+{
+	struct qxl_device *qdev = container_of(work, struct qxl_device, fb_work);
+	unsigned long flags;
+	struct qxl_fb_op *entry, *tmp;
+	struct qxl_fbdev *qfbdev = qdev->mode_info.qfbdev;
+
+	/* since the irq context just adds entries to the end of the
+	   list dropping the lock should be fine, as entry isn't modified
+	   in the operation code */
+	spin_lock_irqsave(&qfbdev->delayed_ops_lock, flags);
+	list_for_each_entry_safe(entry, tmp, &qfbdev->delayed_ops, head) {
+		spin_unlock_irqrestore(&qfbdev->delayed_ops_lock, flags);
+		switch (entry->op_type) {
+		case QXL_FB_OP_FILLRECT:
+			qxl_fb_fillrect_internal(qfbdev->helper.fbdev, &entry->op.fr);
+			break;
+		case QXL_FB_OP_COPYAREA:
+			qxl_fb_copyarea_internal(qfbdev->helper.fbdev, &entry->op.ca);
+			break;
+		case QXL_FB_OP_IMAGEBLIT:
+			qxl_fb_imageblit_internal(qfbdev->helper.fbdev, &entry->op.ib);
+			break;
+		}
+		spin_lock_irqsave(&qfbdev->delayed_ops_lock, flags);
+		list_del(&entry->head);
+		kfree(entry);
+	}
+	spin_unlock_irqrestore(&qfbdev->delayed_ops_lock, flags);
 }
 
 int qxl_fb_init(struct qxl_device *qdev)
 {
+	INIT_WORK(&qdev->fb_work, qxl_fb_work);
 	return 0;
 }
 
@@ -536,7 +677,8 @@ int qxl_fbdev_init(struct qxl_device *qdev)
 	qfbdev->qdev = qdev;
 	qdev->mode_info.qfbdev = qfbdev;
 	qfbdev->helper.funcs = &qxl_fb_helper_funcs;
-
+	spin_lock_init(&qfbdev->delayed_ops_lock);
+	INIT_LIST_HEAD(&qfbdev->delayed_ops);
 	ret = drm_fb_helper_init(qdev->ddev, &qfbdev->helper,
 				 qxl_num_crtc /* num_crtc - QXL supports just 1 */,
 				 QXLFB_CONN_LIMIT);