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

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

3 files changed, 90 insertions, 0 deletions

diff --git a/drivers/char/drm/drmP.h b/drivers/char/drm/drmP.h
index 01e1f2528659..2f18329c5eb8 100644
--- a/drivers/char/drm/drmP.h
+++ b/drivers/char/drm/drmP.h
@@ -715,6 +715,8 @@ 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;
@@ -966,6 +968,7 @@ 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);
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);
diff --git a/drivers/char/drm/drm_lock.c b/drivers/char/drm/drm_lock.c
index f9e45303498d..e0abe5c68423 100644
--- a/drivers/char/drm/drm_lock.c
+++ b/drivers/char/drm/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