Add support for interrupt triggered driver callback with lock held to DRM core.

(cherry picked from d817cc1f30 commit)

linux-core/drmP.h

@@ -919,6 +919,8 @@ typedef struct drm_device {
 	drm_vbl_sig_t vbl_sigs;		/**< signal list to send on VBLANK */
 	drm_vbl_sig_t vbl_sigs2;	/**< signals to send on secondary VBLANK */
 	unsigned int vbl_pending;
+	spinlock_t tasklet_lock;	/**< For drm_locked_tasklet */
+	void (*locked_tasklet_func)(struct drm_device *dev);
 
 	/*@} */
 	cycles_t ctx_start;
@@ -1230,6 +1232,7 @@ extern int drm_wait_vblank(struct inode *inode, struct file *filp,
 			   unsigned int cmd, unsigned long arg);
 extern int drm_vblank_wait(drm_device_t * dev, unsigned int *vbl_seq);
 extern void drm_vbl_send_signals(drm_device_t * dev);
+extern void drm_locked_tasklet(drm_device_t *dev, void(*func)(drm_device_t*));
 
 				/* AGP/GART support (drm_agpsupport.h) */
 extern drm_agp_head_t *drm_agp_init(drm_device_t *dev);

linux-core/drm_irq.c

@@ -118,6 +118,7 @@ static int drm_irq_install(drm_device_t * dev)
 		init_waitqueue_head(&dev->vbl_queue);
 
 		spin_lock_init(&dev->vbl_lock);
+		spin_lock_init(&dev->tasklet_lock);
 
 		INIT_LIST_HEAD(&dev->vbl_sigs.head);
 		INIT_LIST_HEAD(&dev->vbl_sigs2.head);
@@ -396,3 +397,76 @@ void drm_vbl_send_signals(drm_device_t * dev)
 	spin_unlock_irqrestore(&dev->vbl_lock, flags);
 }
 EXPORT_SYMBOL(drm_vbl_send_signals);
+
+/**
+ * Tasklet wrapper function.
+ *
+ * \param data DRM device in disguise.
+ *
+ * Attempts to grab the HW lock and calls the driver callback on success. On
+ * failure, leave the lock marked as contended so the callback can be called
+ * from drm_unlock().
+ */
+static void drm_locked_tasklet_func(unsigned long data)
+{
+	drm_device_t *dev = (drm_device_t*)data;
+	unsigned int irqflags;
+
+	spin_lock_irqsave(&dev->tasklet_lock, irqflags);
+
+	if (!dev->locked_tasklet_func ||
+	    !drm_lock_take(&dev->lock.hw_lock->lock,
+			   DRM_KERNEL_CONTEXT)) {
+		spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
+		return;
+	}
+
+	dev->lock.lock_time = jiffies;
+	atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
+
+	dev->locked_tasklet_func(dev);
+
+	drm_lock_free(dev, &dev->lock.hw_lock->lock,
+		      DRM_KERNEL_CONTEXT);
+
+	dev->locked_tasklet_func = NULL;
+
+	spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
+}
+
+/**
+ * Schedule a tasklet to call back a driver hook with the HW lock held.
+ *
+ * \param dev DRM device.
+ * \param func Driver callback.
+ *
+ * This is intended for triggering actions that require the HW lock from an
+ * interrupt handler. The lock will be grabbed ASAP after the interrupt handler
+ * completes. Note that the callback may be called from interrupt or process
+ * context, it must not make any assumptions about this. Also, the HW lock will
+ * be held with the kernel context or any client context.
+ */
+void drm_locked_tasklet(drm_device_t *dev, void (*func)(drm_device_t*))
+{
+	unsigned int irqflags;
+	static DECLARE_TASKLET(drm_tasklet, drm_locked_tasklet_func, 0);
+
+	if (test_bit(TASKLET_STATE_SCHED, &drm_tasklet.state))
+		return;
+
+	spin_lock_irqsave(&dev->tasklet_lock, irqflags);
+
+	if (dev->locked_tasklet_func) {
+		spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
+		return;
+	}
+
+	dev->locked_tasklet_func = func;
+
+	spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
+
+	drm_tasklet.data = (unsigned long)dev;
+
+	tasklet_hi_schedule(&drm_tasklet);
+}
+EXPORT_SYMBOL(drm_locked_tasklet);

linux-core/drm_lock.c

@@ -155,6 +155,7 @@ int drm_unlock(struct inode *inode, struct file *filp,
 	drm_file_t *priv = filp->private_data;
 	drm_device_t *dev = priv->head->dev;
 	drm_lock_t lock;
+	unsigned int irqflags;
 
 	if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
 		return -EFAULT;
@@ -165,6 +166,16 @@ int drm_unlock(struct inode *inode, struct file *filp,
 		return -EINVAL;
 	}
 
+	spin_lock_irqsave(&dev->tasklet_lock, irqflags);
+
+	if (dev->locked_tasklet_func) {
+		dev->locked_tasklet_func(dev);
+
+		dev->locked_tasklet_func = NULL;
+	}
+
+	spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
+
 	atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 
 	/* kernel_context_switch isn't used by any of the x86 drm