drm: Rework vblank-wait handling to allow interrupt reduction.

Previously, drivers supporting vblank interrupt waits would run the interrupt
all the time, or all the time that any 3d client was running, preventing the
CPU from sleeping for long when the system was otherwise idle.  Now, interrupts
are disabled any time that no client is waiting on a vblank event. The new
method uses vblank counters on the chipsets when the interrupts are turned
off, rather than counting interrupts, so that we can continue to present
accurate vblank numbers.

Co-author: Michel Dänzer <michel@tungstengraphics.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 53 insertions, 21 deletions

diff --git a/drivers/gpu/drm/mga/mga_irq.c b/drivers/gpu/drm/mga/mga_irq.c
index 9302cb8f0f83..bab42f41188b 100644
--- a/drivers/gpu/drm/mga/mga_irq.c
+++ b/drivers/gpu/drm/mga/mga_irq.c
@@ -1,5 +1,6 @@
 /* mga_irq.c -- IRQ handling for radeon -*- linux-c -*-
- *
+ */
+/*
  * Copyright (C) The Weather Channel, Inc.  2002.  All Rights Reserved.
  *
  * The Weather Channel (TM) funded Tungsten Graphics to develop the
@@ -35,6 +36,18 @@
 #include "mga_drm.h"
 #include "mga_drv.h"
 
+u32 mga_get_vblank_counter(struct drm_device *dev, int crtc)
+{
+	const drm_mga_private_t *const dev_priv =
+		(drm_mga_private_t *) dev->dev_private;
+
+	if (crtc != 0)
+		return 0;
+
+	return atomic_read(&dev_priv->vbl_received);
+}
+
+
 irqreturn_t mga_driver_irq_handler(DRM_IRQ_ARGS)
 {
 	struct drm_device *dev = (struct drm_device *) arg;
@@ -47,9 +60,8 @@ irqreturn_t mga_driver_irq_handler(DRM_IRQ_ARGS)
 	/* VBLANK interrupt */
 	if (status & MGA_VLINEPEN) {
 		MGA_WRITE(MGA_ICLEAR, MGA_VLINEICLR);
-		atomic_inc(&dev->vbl_received);
-		DRM_WAKEUP(&dev->vbl_queue);
-		drm_vbl_send_signals(dev);
+		atomic_inc(&dev_priv->vbl_received);
+		drm_handle_vblank(dev, 0);
 		handled = 1;
 	}
 
@@ -58,6 +70,7 @@ irqreturn_t mga_driver_irq_handler(DRM_IRQ_ARGS)
 		const u32 prim_start = MGA_READ(MGA_PRIMADDRESS);
 		const u32 prim_end = MGA_READ(MGA_PRIMEND);
 
+
 		MGA_WRITE(MGA_ICLEAR, MGA_SOFTRAPICLR);
 
 		/* In addition to clearing the interrupt-pending bit, we
@@ -72,28 +85,39 @@ irqreturn_t mga_driver_irq_handler(DRM_IRQ_ARGS)
 		handled = 1;
 	}
 
-	if (handled) {
+	if (handled)
 		return IRQ_HANDLED;
-	}
 	return IRQ_NONE;
 }
 
-int mga_driver_vblank_wait(struct drm_device * dev, unsigned int *sequence)
+int mga_enable_vblank(struct drm_device *dev, int crtc)
 {
-	unsigned int cur_vblank;
-	int ret = 0;
+	drm_mga_private_t *dev_priv = (drm_mga_private_t *) dev->dev_private;
 
-	/* Assume that the user has missed the current sequence number
-	 * by about a day rather than she wants to wait for years
-	 * using vertical blanks...
-	 */
-	DRM_WAIT_ON(ret, dev->vbl_queue, 3 * DRM_HZ,
-		    (((cur_vblank = atomic_read(&dev->vbl_received))
-		      - *sequence) <= (1 << 23)));
+	if (crtc != 0) {
+		DRM_ERROR("tried to enable vblank on non-existent crtc %d\n",
+			  crtc);
+		return 0;
+	}
 
-	*sequence = cur_vblank;
+	MGA_WRITE(MGA_IEN, MGA_VLINEIEN | MGA_SOFTRAPEN);
+	return 0;
+}
 
-	return ret;
+
+void mga_disable_vblank(struct drm_device *dev, int crtc)
+{
+	if (crtc != 0) {
+		DRM_ERROR("tried to disable vblank on non-existent crtc %d\n",
+			  crtc);
+	}
+
+	/* Do *NOT* disable the vertical refresh interrupt.  MGA doesn't have
+	 * a nice hardware counter that tracks the number of refreshes when
+	 * the interrupt is disabled, and the kernel doesn't know the refresh
+	 * rate to calculate an estimate.
+	 */
+	/* MGA_WRITE(MGA_IEN, MGA_VLINEIEN | MGA_SOFTRAPEN); */
 }
 
 int mga_driver_fence_wait(struct drm_device * dev, unsigned int *sequence)
@@ -125,14 +149,22 @@ void mga_driver_irq_preinstall(struct drm_device * dev)
 	MGA_WRITE(MGA_ICLEAR, ~0);
 }
 
-void mga_driver_irq_postinstall(struct drm_device * dev)
+int mga_driver_irq_postinstall(struct drm_device *dev)
 {
 	drm_mga_private_t *dev_priv = (drm_mga_private_t *) dev->dev_private;
+	int ret;
+
+	ret = drm_vblank_init(dev, 1);
+	if (ret)
+		return ret;
 
 	DRM_INIT_WAITQUEUE(&dev_priv->fence_queue);
 
-	/* Turn on vertical blank interrupt and soft trap interrupt. */
-	MGA_WRITE(MGA_IEN, MGA_VLINEIEN | MGA_SOFTRAPEN);
+	/* Turn on soft trap interrupt.  Vertical blank interrupts are enabled
+	 * in mga_enable_vblank.
+	 */
+	MGA_WRITE(MGA_IEN, MGA_SOFTRAPEN);
+	return 0;
 }
 
 void mga_driver_irq_uninstall(struct drm_device * dev)