drm/i915: i8xx interrupt handler

gen2 hardware has some significant differences from the other interrupt
routines that were glossed over and then forgotten about in the
transition to KMS. Such as

- 16bit IIR
- PendingFlip status bit

This patch reintroduces a handler specifically for gen2 for the purpose
of handling pageflips correctly, simplifying code in the process.

v2: Also fixup ring get/put irq to only access 16bit registers (Daniel)

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=24202
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41793
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: use posting_read16 in intel_ringbuffer.c and kill _driver
from the function names.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -2446,6 +2446,152 @@ static void i915_driver_irq_uninstall(struct drm_device * dev)
 	I915_WRITE(IIR, I915_READ(IIR));
 }
 
+static void i8xx_irq_preinstall(struct drm_device * dev)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+	int pipe;
+
+	atomic_set(&dev_priv->irq_received, 0);
+
+	for_each_pipe(pipe)
+		I915_WRITE(PIPESTAT(pipe), 0);
+	I915_WRITE16(IMR, 0xffff);
+	I915_WRITE16(IER, 0x0);
+	POSTING_READ16(IER);
+}
+
+static int i8xx_irq_postinstall(struct drm_device *dev)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+
+	dev_priv->vblank_pipe = DRM_I915_VBLANK_PIPE_A | DRM_I915_VBLANK_PIPE_B;
+
+	dev_priv->pipestat[0] = 0;
+	dev_priv->pipestat[1] = 0;
+
+	I915_WRITE16(EMR,
+		     ~(I915_ERROR_PAGE_TABLE | I915_ERROR_MEMORY_REFRESH));
+
+	/* Unmask the interrupts that we always want on. */
+	dev_priv->irq_mask =
+		~(I915_DISPLAY_PIPE_A_EVENT_INTERRUPT |
+		  I915_DISPLAY_PIPE_B_EVENT_INTERRUPT |
+		  I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT |
+		  I915_DISPLAY_PLANE_B_FLIP_PENDING_INTERRUPT |
+		  I915_RENDER_COMMAND_PARSER_ERROR_INTERRUPT);
+	I915_WRITE16(IMR, dev_priv->irq_mask);
+
+	I915_WRITE16(IER,
+		     I915_DISPLAY_PIPE_A_EVENT_INTERRUPT |
+		     I915_DISPLAY_PIPE_B_EVENT_INTERRUPT |
+		     I915_RENDER_COMMAND_PARSER_ERROR_INTERRUPT |
+		     I915_USER_INTERRUPT);
+	POSTING_READ16(IER);
+
+	return 0;
+}
+
+static irqreturn_t i8xx_irq_handler(DRM_IRQ_ARGS)
+{
+	struct drm_device *dev = (struct drm_device *) arg;
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+	struct drm_i915_master_private *master_priv;
+	u16 iir, new_iir;
+	u32 pipe_stats[2];
+	unsigned long irqflags;
+	int irq_received;
+	int pipe;
+	u16 flip_mask =
+		I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT |
+		I915_DISPLAY_PLANE_B_FLIP_PENDING_INTERRUPT;
+
+	atomic_inc(&dev_priv->irq_received);
+
+	iir = I915_READ16(IIR);
+	if (iir == 0)
+		return IRQ_NONE;
+
+	while (iir & ~flip_mask) {
+		/* Can't rely on pipestat interrupt bit in iir as it might
+		 * have been cleared after the pipestat interrupt was received.
+		 * It doesn't set the bit in iir again, but it still produces
+		 * interrupts (for non-MSI).
+		 */
+		spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+		if (iir & I915_RENDER_COMMAND_PARSER_ERROR_INTERRUPT)
+			i915_handle_error(dev, false);
+
+		for_each_pipe(pipe) {
+			int reg = PIPESTAT(pipe);
+			pipe_stats[pipe] = I915_READ(reg);
+
+			/*
+			 * Clear the PIPE*STAT regs before the IIR
+			 */
+			if (pipe_stats[pipe] & 0x8000ffff) {
+				if (pipe_stats[pipe] & PIPE_FIFO_UNDERRUN_STATUS)
+					DRM_DEBUG_DRIVER("pipe %c underrun\n",
+							 pipe_name(pipe));
+				I915_WRITE(reg, pipe_stats[pipe]);
+				irq_received = 1;
+			}
+		}
+		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
+
+		I915_WRITE16(IIR, iir & ~flip_mask);
+		new_iir = I915_READ16(IIR); /* Flush posted writes */
+
+		if (dev->primary->master) {
+			master_priv = dev->primary->master->driver_priv;
+			if (master_priv->sarea_priv)
+				master_priv->sarea_priv->last_dispatch =
+					READ_BREADCRUMB(dev_priv);
+		}
+
+		if (iir & I915_USER_INTERRUPT)
+			notify_ring(dev, &dev_priv->ring[RCS]);
+
+		if (pipe_stats[0] & PIPE_VBLANK_INTERRUPT_STATUS &&
+		    drm_handle_vblank(dev, 0)) {
+			if (iir & I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT) {
+				intel_prepare_page_flip(dev, 0);
+				intel_finish_page_flip(dev, 0);
+				flip_mask &= ~I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT;
+			}
+		}
+
+		if (pipe_stats[1] & PIPE_VBLANK_INTERRUPT_STATUS &&
+		    drm_handle_vblank(dev, 1)) {
+			if (iir & I915_DISPLAY_PLANE_B_FLIP_PENDING_INTERRUPT) {
+				intel_prepare_page_flip(dev, 1);
+				intel_finish_page_flip(dev, 1);
+				flip_mask &= ~I915_DISPLAY_PLANE_B_FLIP_PENDING_INTERRUPT;
+			}
+		}
+
+		iir = new_iir;
+	}
+
+	return IRQ_HANDLED;
+}
+
+static void i8xx_irq_uninstall(struct drm_device * dev)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+	int pipe;
+
+	dev_priv->vblank_pipe = 0;
+
+	for_each_pipe(pipe) {
+		/* Clear enable bits; then clear status bits */
+		I915_WRITE(PIPESTAT(pipe), 0);
+		I915_WRITE(PIPESTAT(pipe), I915_READ(PIPESTAT(pipe)));
+	}
+	I915_WRITE16(IMR, 0xffff);
+	I915_WRITE16(IER, 0x0);
+	I915_WRITE16(IIR, I915_READ16(IIR));
+}
+
 void intel_irq_init(struct drm_device *dev)
 {
 	dev->driver->get_vblank_counter = i915_get_vblank_counter;
@@ -2485,10 +2631,17 @@ void intel_irq_init(struct drm_device *dev)
 		dev->driver->enable_vblank = ironlake_enable_vblank;
 		dev->driver->disable_vblank = ironlake_disable_vblank;
 	} else {
-		dev->driver->irq_preinstall = i915_driver_irq_preinstall;
-		dev->driver->irq_postinstall = i915_driver_irq_postinstall;
-		dev->driver->irq_uninstall = i915_driver_irq_uninstall;
-		dev->driver->irq_handler = i915_driver_irq_handler;
+		if (INTEL_INFO(dev)->gen == 2) {
+			dev->driver->irq_preinstall = i8xx_irq_preinstall;
+			dev->driver->irq_postinstall = i8xx_irq_postinstall;
+			dev->driver->irq_handler = i8xx_irq_handler;
+			dev->driver->irq_uninstall = i8xx_irq_uninstall;
+		} else {
+			dev->driver->irq_preinstall = i915_driver_irq_preinstall;
+			dev->driver->irq_postinstall = i915_driver_irq_postinstall;
+			dev->driver->irq_uninstall = i915_driver_irq_uninstall;
+			dev->driver->irq_handler = i915_driver_irq_handler;
+		}
 		dev->driver->enable_vblank = i915_enable_vblank;
 		dev->driver->disable_vblank = i915_disable_vblank;
 	}

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -678,6 +678,41 @@ i9xx_ring_put_irq(struct intel_ring_buffer *ring)
 	spin_unlock(&ring->irq_lock);
 }
 
+static bool
+i8xx_ring_get_irq(struct intel_ring_buffer *ring)
+{
+	struct drm_device *dev = ring->dev;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+
+	if (!dev->irq_enabled)
+		return false;
+
+	spin_lock(&ring->irq_lock);
+	if (ring->irq_refcount++ == 0) {
+		dev_priv->irq_mask &= ~ring->irq_enable_mask;
+		I915_WRITE16(IMR, dev_priv->irq_mask);
+		POSTING_READ16(IMR);
+	}
+	spin_unlock(&ring->irq_lock);
+
+	return true;
+}
+
+static void
+i8xx_ring_put_irq(struct intel_ring_buffer *ring)
+{
+	struct drm_device *dev = ring->dev;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+
+	spin_lock(&ring->irq_lock);
+	if (--ring->irq_refcount == 0) {
+		dev_priv->irq_mask |= ring->irq_enable_mask;
+		I915_WRITE16(IMR, dev_priv->irq_mask);
+		POSTING_READ16(IMR);
+	}
+	spin_unlock(&ring->irq_lock);
+}
+
 void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
 {
 	struct drm_device *dev = ring->dev;
@@ -1310,8 +1345,13 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
 		else
 			ring->flush = gen4_render_ring_flush;
 		ring->get_seqno = ring_get_seqno;
-		ring->irq_get = i9xx_ring_get_irq;
-		ring->irq_put = i9xx_ring_put_irq;
+		if (IS_GEN2(dev)) {
+			ring->irq_get = i8xx_ring_get_irq;
+			ring->irq_put = i8xx_ring_put_irq;
+		} else {
+			ring->irq_get = i9xx_ring_get_irq;
+			ring->irq_put = i9xx_ring_put_irq;
+		}
 		ring->irq_enable_mask = I915_USER_INTERRUPT;
 	}
 	ring->write_tail = ring_write_tail;
@@ -1358,8 +1398,13 @@ int intel_render_ring_init_dri(struct drm_device *dev, u64 start, u32 size)
 	else
 		ring->flush = gen4_render_ring_flush;
 	ring->get_seqno = ring_get_seqno;
-	ring->irq_get = i9xx_ring_get_irq;
-	ring->irq_put = i9xx_ring_put_irq;
+	if (IS_GEN2(dev)) {
+		ring->irq_get = i8xx_ring_get_irq;
+		ring->irq_put = i8xx_ring_put_irq;
+	} else {
+		ring->irq_get = i9xx_ring_get_irq;
+		ring->irq_put = i9xx_ring_put_irq;
+	}
 	ring->irq_enable_mask = I915_USER_INTERRUPT;
 	ring->write_tail = ring_write_tail;
 	if (INTEL_INFO(dev)->gen >= 4)