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

Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 76 insertions, 0 deletions

diff --git a/drivers/char/drm/drm_irq.c b/drivers/char/drm/drm_irq.c
index 3c77756aad9c..2b10e5b60cfa 100644
--- a/drivers/char/drm/drm_irq.c
+++ b/drivers/char/drm/drm_irq.c
@@ -119,6 +119,7 @@ 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);
@@ -176,6 +177,8 @@ int drm_irq_uninstall(drm_device_t * dev)
 
         free_irq(dev->irq, dev);
 
+        dev->locked_tasklet_func = NULL;
+
         return 0;
 }
 
@@ -399,3 +402,76 @@ void drm_vbl_send_signals(drm_device_t * dev)
 }
 
 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 long 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 long 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);