[deliverable/linux.git] / drivers / gpu / drm / i915 / intel_ringbuffer.c

/*
 * Copyright © 2008-2010 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Eric Anholt <eric@anholt.net>
 *    Zou Nan hai <nanhai.zou@intel.com>
 *    Xiang Hai hao<haihao.xiang@intel.com>
 *
 */

#include "drmP.h"
#include "drm.h"
#include "i915_drv.h"
#include "i915_drm.h"
#include "i915_trace.h"
#include "intel_drv.h"

/*
 * 965+ support PIPE_CONTROL commands, which provide finer grained control
 * over cache flushing.
 */
struct pipe_control {
	struct drm_i915_gem_object *obj;
	volatile u32 *cpu_page;
	u32 gtt_offset;
};

static inline int ring_space(struct intel_ring_buffer *ring)
{
	int space = (ring->head & HEAD_ADDR) - (ring->tail + 8);
	if (space < 0)
		space += ring->size;
	return space;
}

static int
gen2_render_ring_flush(struct intel_ring_buffer *ring,
		       u32	invalidate_domains,
		       u32	flush_domains)
{
	u32 cmd;
	int ret;

	cmd = MI_FLUSH;
	if (((invalidate_domains|flush_domains) & I915_GEM_DOMAIN_RENDER) == 0)
		cmd |= MI_NO_WRITE_FLUSH;

	if (invalidate_domains & I915_GEM_DOMAIN_SAMPLER)
		cmd |= MI_READ_FLUSH;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring, cmd);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);

	return 0;
}

static int
gen4_render_ring_flush(struct intel_ring_buffer *ring,
		       u32	invalidate_domains,
		       u32	flush_domains)
{
	struct drm_device *dev = ring->dev;
	u32 cmd;
	int ret;

	/*
	 * read/write caches:
	 *
	 * I915_GEM_DOMAIN_RENDER is always invalidated, but is
	 * only flushed if MI_NO_WRITE_FLUSH is unset.  On 965, it is
	 * also flushed at 2d versus 3d pipeline switches.
	 *
	 * read-only caches:
	 *
	 * I915_GEM_DOMAIN_SAMPLER is flushed on pre-965 if
	 * MI_READ_FLUSH is set, and is always flushed on 965.
	 *
	 * I915_GEM_DOMAIN_COMMAND may not exist?
	 *
	 * I915_GEM_DOMAIN_INSTRUCTION, which exists on 965, is
	 * invalidated when MI_EXE_FLUSH is set.
	 *
	 * I915_GEM_DOMAIN_VERTEX, which exists on 965, is
	 * invalidated with every MI_FLUSH.
	 *
	 * TLBs:
	 *
	 * On 965, TLBs associated with I915_GEM_DOMAIN_COMMAND
	 * and I915_GEM_DOMAIN_CPU in are invalidated at PTE write and
	 * I915_GEM_DOMAIN_RENDER and I915_GEM_DOMAIN_SAMPLER
	 * are flushed at any MI_FLUSH.
	 */

	cmd = MI_FLUSH | MI_NO_WRITE_FLUSH;
	if ((invalidate_domains|flush_domains) & I915_GEM_DOMAIN_RENDER)
		cmd &= ~MI_NO_WRITE_FLUSH;
	if (invalidate_domains & I915_GEM_DOMAIN_INSTRUCTION)
		cmd |= MI_EXE_FLUSH;

	if (invalidate_domains & I915_GEM_DOMAIN_COMMAND &&
	    (IS_G4X(dev) || IS_GEN5(dev)))
		cmd |= MI_INVALIDATE_ISP;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring, cmd);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);

	return 0;
}

/**
 * Emits a PIPE_CONTROL with a non-zero post-sync operation, for
 * implementing two workarounds on gen6.  From section 1.4.7.1
 * "PIPE_CONTROL" of the Sandy Bridge PRM volume 2 part 1:
 *
 * [DevSNB-C+{W/A}] Before any depth stall flush (including those
 * produced by non-pipelined state commands), software needs to first
 * send a PIPE_CONTROL with no bits set except Post-Sync Operation !=
 * 0.
 *
 * [Dev-SNB{W/A}]: Before a PIPE_CONTROL with Write Cache Flush Enable
 * =1, a PIPE_CONTROL with any non-zero post-sync-op is required.
 *
 * And the workaround for these two requires this workaround first:
 *
 * [Dev-SNB{W/A}]: Pipe-control with CS-stall bit set must be sent
 * BEFORE the pipe-control with a post-sync op and no write-cache
 * flushes.
 *
 * And this last workaround is tricky because of the requirements on
 * that bit.  From section 1.4.7.2.3 "Stall" of the Sandy Bridge PRM
 * volume 2 part 1:
 *
 *     "1 of the following must also be set:
 *      - Render Target Cache Flush Enable ([12] of DW1)
 *      - Depth Cache Flush Enable ([0] of DW1)
 *      - Stall at Pixel Scoreboard ([1] of DW1)
 *      - Depth Stall ([13] of DW1)
 *      - Post-Sync Operation ([13] of DW1)
 *      - Notify Enable ([8] of DW1)"
 *
 * The cache flushes require the workaround flush that triggered this
 * one, so we can't use it.  Depth stall would trigger the same.
 * Post-sync nonzero is what triggered this second workaround, so we
 * can't use that one either.  Notify enable is IRQs, which aren't
 * really our business.  That leaves only stall at scoreboard.
 */
static int
intel_emit_post_sync_nonzero_flush(struct intel_ring_buffer *ring)
{
	struct pipe_control *pc = ring->private;
	u32 scratch_addr = pc->gtt_offset + 128;
	int ret;


	ret = intel_ring_begin(ring, 6);
	if (ret)
		return ret;

	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(5));
	intel_ring_emit(ring, PIPE_CONTROL_CS_STALL |
			PIPE_CONTROL_STALL_AT_SCOREBOARD);
	intel_ring_emit(ring, scratch_addr | PIPE_CONTROL_GLOBAL_GTT); /* address */
	intel_ring_emit(ring, 0); /* low dword */
	intel_ring_emit(ring, 0); /* high dword */
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);

	ret = intel_ring_begin(ring, 6);
	if (ret)
		return ret;

	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(5));
	intel_ring_emit(ring, PIPE_CONTROL_QW_WRITE);
	intel_ring_emit(ring, scratch_addr | PIPE_CONTROL_GLOBAL_GTT); /* address */
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);

	return 0;
}

static int
gen6_render_ring_flush(struct intel_ring_buffer *ring,
                         u32 invalidate_domains, u32 flush_domains)
{
	u32 flags = 0;
	struct pipe_control *pc = ring->private;
	u32 scratch_addr = pc->gtt_offset + 128;
	int ret;

	/* Force SNB workarounds for PIPE_CONTROL flushes */
	intel_emit_post_sync_nonzero_flush(ring);

	/* Just flush everything.  Experiments have shown that reducing the
	 * number of bits based on the write domains has little performance
	 * impact.
	 */
	flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
	flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
	flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
	flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
	flags |= PIPE_CONTROL_VF_CACHE_INVALIDATE;
	flags |= PIPE_CONTROL_CONST_CACHE_INVALIDATE;
	flags |= PIPE_CONTROL_STATE_CACHE_INVALIDATE;

	ret = intel_ring_begin(ring, 6);
	if (ret)
		return ret;

	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(5));
	intel_ring_emit(ring, flags);
	intel_ring_emit(ring, scratch_addr | PIPE_CONTROL_GLOBAL_GTT);
	intel_ring_emit(ring, 0); /* lower dword */
	intel_ring_emit(ring, 0); /* uppwer dword */
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);

	return 0;
}

static void ring_write_tail(struct intel_ring_buffer *ring,
			    u32 value)
{
	drm_i915_private_t *dev_priv = ring->dev->dev_private;
	I915_WRITE_TAIL(ring, value);
}

u32 intel_ring_get_active_head(struct intel_ring_buffer *ring)
{
	drm_i915_private_t *dev_priv = ring->dev->dev_private;
	u32 acthd_reg = INTEL_INFO(ring->dev)->gen >= 4 ?
			RING_ACTHD(ring->mmio_base) : ACTHD;

	return I915_READ(acthd_reg);
}

static int init_ring_common(struct intel_ring_buffer *ring)
{
	drm_i915_private_t *dev_priv = ring->dev->dev_private;
	struct drm_i915_gem_object *obj = ring->obj;
	u32 head;

	/* Stop the ring if it's running. */
	I915_WRITE_CTL(ring, 0);
	I915_WRITE_HEAD(ring, 0);
	ring->write_tail(ring, 0);

	/* Initialize the ring. */
	I915_WRITE_START(ring, obj->gtt_offset);
	head = I915_READ_HEAD(ring) & HEAD_ADDR;

	/* G45 ring initialization fails to reset head to zero */
	if (head != 0) {
		DRM_DEBUG_KMS("%s head not reset to zero "
			      "ctl %08x head %08x tail %08x start %08x\n",
			      ring->name,
			      I915_READ_CTL(ring),
			      I915_READ_HEAD(ring),
			      I915_READ_TAIL(ring),
			      I915_READ_START(ring));

		I915_WRITE_HEAD(ring, 0);

		if (I915_READ_HEAD(ring) & HEAD_ADDR) {
			DRM_ERROR("failed to set %s head to zero "
				  "ctl %08x head %08x tail %08x start %08x\n",
				  ring->name,
				  I915_READ_CTL(ring),
				  I915_READ_HEAD(ring),
				  I915_READ_TAIL(ring),
				  I915_READ_START(ring));
		}
	}

	I915_WRITE_CTL(ring,
			((ring->size - PAGE_SIZE) & RING_NR_PAGES)
			| RING_VALID);

	/* If the head is still not zero, the ring is dead */
	if (wait_for((I915_READ_CTL(ring) & RING_VALID) != 0 &&
		     I915_READ_START(ring) == obj->gtt_offset &&
		     (I915_READ_HEAD(ring) & HEAD_ADDR) == 0, 50)) {
		DRM_ERROR("%s initialization failed "
				"ctl %08x head %08x tail %08x start %08x\n",
				ring->name,
				I915_READ_CTL(ring),
				I915_READ_HEAD(ring),
				I915_READ_TAIL(ring),
				I915_READ_START(ring));
		return -EIO;
	}

	if (!drm_core_check_feature(ring->dev, DRIVER_MODESET))
		i915_kernel_lost_context(ring->dev);
	else {
		ring->head = I915_READ_HEAD(ring);
		ring->tail = I915_READ_TAIL(ring) & TAIL_ADDR;
		ring->space = ring_space(ring);
		ring->last_retired_head = -1;
	}

	return 0;
}

static int
init_pipe_control(struct intel_ring_buffer *ring)
{
	struct pipe_control *pc;
	struct drm_i915_gem_object *obj;
	int ret;

	if (ring->private)
		return 0;

	pc = kmalloc(sizeof(*pc), GFP_KERNEL);
	if (!pc)
		return -ENOMEM;

	obj = i915_gem_alloc_object(ring->dev, 4096);
	if (obj == NULL) {
		DRM_ERROR("Failed to allocate seqno page\n");
		ret = -ENOMEM;
		goto err;
	}

	i915_gem_object_set_cache_level(obj, I915_CACHE_LLC);

	ret = i915_gem_object_pin(obj, 4096, true);
	if (ret)
		goto err_unref;

	pc->gtt_offset = obj->gtt_offset;
	pc->cpu_page =  kmap(obj->pages[0]);
	if (pc->cpu_page == NULL)
		goto err_unpin;

	pc->obj = obj;
	ring->private = pc;
	return 0;

err_unpin:
	i915_gem_object_unpin(obj);
err_unref:
	drm_gem_object_unreference(&obj->base);
err:
	kfree(pc);
	return ret;
}

static void
cleanup_pipe_control(struct intel_ring_buffer *ring)
{
	struct pipe_control *pc = ring->private;
	struct drm_i915_gem_object *obj;

	if (!ring->private)
		return;

	obj = pc->obj;
	kunmap(obj->pages[0]);
	i915_gem_object_unpin(obj);
	drm_gem_object_unreference(&obj->base);

	kfree(pc);
	ring->private = NULL;
}

static int init_render_ring(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	struct drm_i915_private *dev_priv = dev->dev_private;
	int ret = init_ring_common(ring);

	if (INTEL_INFO(dev)->gen > 3) {
		I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(VS_TIMER_DISPATCH));
		if (IS_GEN7(dev))
			I915_WRITE(GFX_MODE_GEN7,
				   _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
				   _MASKED_BIT_ENABLE(GFX_REPLAY_MODE));
	}

	if (INTEL_INFO(dev)->gen >= 5) {
		ret = init_pipe_control(ring);
		if (ret)
			return ret;
	}

	if (IS_GEN6(dev)) {
		/* From the Sandybridge PRM, volume 1 part 3, page 24:
		 * "If this bit is set, STCunit will have LRA as replacement
		 *  policy. [...] This bit must be reset.  LRA replacement
		 *  policy is not supported."
		 */
		I915_WRITE(CACHE_MODE_0,
			   _MASKED_BIT_DISABLE(CM0_STC_EVICT_DISABLE_LRA_SNB));
	}

	if (INTEL_INFO(dev)->gen >= 6)
		I915_WRITE(INSTPM, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));

	return ret;
}

static void render_ring_cleanup(struct intel_ring_buffer *ring)
{
	if (!ring->private)
		return;

	cleanup_pipe_control(ring);
}

static void
update_mboxes(struct intel_ring_buffer *ring,
	    u32 seqno,
	    u32 mmio_offset)
{
	intel_ring_emit(ring, MI_SEMAPHORE_MBOX |
			      MI_SEMAPHORE_GLOBAL_GTT |
			      MI_SEMAPHORE_REGISTER |
			      MI_SEMAPHORE_UPDATE);
	intel_ring_emit(ring, seqno);
	intel_ring_emit(ring, mmio_offset);
}

/**
 * gen6_add_request - Update the semaphore mailbox registers
 * 
 * @ring - ring that is adding a request
 * @seqno - return seqno stuck into the ring
 *
 * Update the mailbox registers in the *other* rings with the current seqno.
 * This acts like a signal in the canonical semaphore.
 */
static int
gen6_add_request(struct intel_ring_buffer *ring,
		 u32 *seqno)
{
	u32 mbox1_reg;
	u32 mbox2_reg;
	int ret;

	ret = intel_ring_begin(ring, 10);
	if (ret)
		return ret;

	mbox1_reg = ring->signal_mbox[0];
	mbox2_reg = ring->signal_mbox[1];

	*seqno = i915_gem_next_request_seqno(ring);

	update_mboxes(ring, *seqno, mbox1_reg);
	update_mboxes(ring, *seqno, mbox2_reg);
	intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
	intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
	intel_ring_emit(ring, *seqno);
	intel_ring_emit(ring, MI_USER_INTERRUPT);
	intel_ring_advance(ring);

	return 0;
}

/**
 * intel_ring_sync - sync the waiter to the signaller on seqno
 *
 * @waiter - ring that is waiting
 * @signaller - ring which has, or will signal
 * @seqno - seqno which the waiter will block on
 */
static int
gen6_ring_sync(struct intel_ring_buffer *waiter,
	       struct intel_ring_buffer *signaller,
	       u32 seqno)
{
	int ret;
	u32 dw1 = MI_SEMAPHORE_MBOX |
		  MI_SEMAPHORE_COMPARE |
		  MI_SEMAPHORE_REGISTER;

	/* Throughout all of the GEM code, seqno passed implies our current
	 * seqno is >= the last seqno executed. However for hardware the
	 * comparison is strictly greater than.
	 */
	seqno -= 1;

	WARN_ON(signaller->semaphore_register[waiter->id] ==
		MI_SEMAPHORE_SYNC_INVALID);

	ret = intel_ring_begin(waiter, 4);
	if (ret)
		return ret;

	intel_ring_emit(waiter,
			dw1 | signaller->semaphore_register[waiter->id]);
	intel_ring_emit(waiter, seqno);
	intel_ring_emit(waiter, 0);
	intel_ring_emit(waiter, MI_NOOP);
	intel_ring_advance(waiter);

	return 0;
}

#define PIPE_CONTROL_FLUSH(ring__, addr__)					\
do {									\
	intel_ring_emit(ring__, GFX_OP_PIPE_CONTROL(4) | PIPE_CONTROL_QW_WRITE |		\
		 PIPE_CONTROL_DEPTH_STALL);				\
	intel_ring_emit(ring__, (addr__) | PIPE_CONTROL_GLOBAL_GTT);			\
	intel_ring_emit(ring__, 0);							\
	intel_ring_emit(ring__, 0);							\
} while (0)

static int
pc_render_add_request(struct intel_ring_buffer *ring,
		      u32 *result)
{
	u32 seqno = i915_gem_next_request_seqno(ring);
	struct pipe_control *pc = ring->private;
	u32 scratch_addr = pc->gtt_offset + 128;
	int ret;

	/* For Ironlake, MI_USER_INTERRUPT was deprecated and apparently
	 * incoherent with writes to memory, i.e. completely fubar,
	 * so we need to use PIPE_NOTIFY instead.
	 *
	 * However, we also need to workaround the qword write
	 * incoherence by flushing the 6 PIPE_NOTIFY buffers out to
	 * memory before requesting an interrupt.
	 */
	ret = intel_ring_begin(ring, 32);
	if (ret)
		return ret;

	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(4) | PIPE_CONTROL_QW_WRITE |
			PIPE_CONTROL_WRITE_FLUSH |
			PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE);
	intel_ring_emit(ring, pc->gtt_offset | PIPE_CONTROL_GLOBAL_GTT);
	intel_ring_emit(ring, seqno);
	intel_ring_emit(ring, 0);
	PIPE_CONTROL_FLUSH(ring, scratch_addr);
	scratch_addr += 128; /* write to separate cachelines */
	PIPE_CONTROL_FLUSH(ring, scratch_addr);
	scratch_addr += 128;
	PIPE_CONTROL_FLUSH(ring, scratch_addr);
	scratch_addr += 128;
	PIPE_CONTROL_FLUSH(ring, scratch_addr);
	scratch_addr += 128;
	PIPE_CONTROL_FLUSH(ring, scratch_addr);
	scratch_addr += 128;
	PIPE_CONTROL_FLUSH(ring, scratch_addr);

	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(4) | PIPE_CONTROL_QW_WRITE |
			PIPE_CONTROL_WRITE_FLUSH |
			PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE |
			PIPE_CONTROL_NOTIFY);
	intel_ring_emit(ring, pc->gtt_offset | PIPE_CONTROL_GLOBAL_GTT);
	intel_ring_emit(ring, seqno);
	intel_ring_emit(ring, 0);
	intel_ring_advance(ring);

	*result = seqno;
	return 0;
}

static u32
gen6_ring_get_seqno(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;

	/* Workaround to force correct ordering between irq and seqno writes on
	 * ivb (and maybe also on snb) by reading from a CS register (like
	 * ACTHD) before reading the status page. */
	if (IS_GEN6(dev) || IS_GEN7(dev))
		intel_ring_get_active_head(ring);
	return intel_read_status_page(ring, I915_GEM_HWS_INDEX);
}

static u32
ring_get_seqno(struct intel_ring_buffer *ring)
{
	return intel_read_status_page(ring, I915_GEM_HWS_INDEX);
}

static u32
pc_render_get_seqno(struct intel_ring_buffer *ring)
{
	struct pipe_control *pc = ring->private;
	return pc->cpu_page[0];
}

static bool
gen5_ring_get_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	if (!dev->irq_enabled)
		return false;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (ring->irq_refcount++ == 0) {
		dev_priv->gt_irq_mask &= ~ring->irq_enable_mask;
		I915_WRITE(GTIMR, dev_priv->gt_irq_mask);
		POSTING_READ(GTIMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

	return true;
}

static void
gen5_ring_put_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (--ring->irq_refcount == 0) {
		dev_priv->gt_irq_mask |= ring->irq_enable_mask;
		I915_WRITE(GTIMR, dev_priv->gt_irq_mask);
		POSTING_READ(GTIMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
}

static bool
i9xx_ring_get_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	if (!dev->irq_enabled)
		return false;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (ring->irq_refcount++ == 0) {
		dev_priv->irq_mask &= ~ring->irq_enable_mask;
		I915_WRITE(IMR, dev_priv->irq_mask);
		POSTING_READ(IMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

	return true;
}

static void
i9xx_ring_put_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (--ring->irq_refcount == 0) {
		dev_priv->irq_mask |= ring->irq_enable_mask;
		I915_WRITE(IMR, dev_priv->irq_mask);
		POSTING_READ(IMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
}

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;
	unsigned long flags;

	if (!dev->irq_enabled)
		return false;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	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_irqrestore(&dev_priv->irq_lock, flags);

	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;
	unsigned long flags;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	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_irqrestore(&dev_priv->irq_lock, flags);
}

void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = ring->dev->dev_private;
	u32 mmio = 0;

	/* The ring status page addresses are no longer next to the rest of
	 * the ring registers as of gen7.
	 */
	if (IS_GEN7(dev)) {
		switch (ring->id) {
		case RCS:
			mmio = RENDER_HWS_PGA_GEN7;
			break;
		case BCS:
			mmio = BLT_HWS_PGA_GEN7;
			break;
		case VCS:
			mmio = BSD_HWS_PGA_GEN7;
			break;
		}
	} else if (IS_GEN6(ring->dev)) {
		mmio = RING_HWS_PGA_GEN6(ring->mmio_base);
	} else {
		mmio = RING_HWS_PGA(ring->mmio_base);
	}

	I915_WRITE(mmio, (u32)ring->status_page.gfx_addr);
	POSTING_READ(mmio);
}

static int
bsd_ring_flush(struct intel_ring_buffer *ring,
	       u32     invalidate_domains,
	       u32     flush_domains)
{
	int ret;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring, MI_FLUSH);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);
	return 0;
}

static int
i9xx_add_request(struct intel_ring_buffer *ring,
		 u32 *result)
{
	u32 seqno;
	int ret;

	ret = intel_ring_begin(ring, 4);
	if (ret)
		return ret;

	seqno = i915_gem_next_request_seqno(ring);

	intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
	intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
	intel_ring_emit(ring, seqno);
	intel_ring_emit(ring, MI_USER_INTERRUPT);
	intel_ring_advance(ring);

	*result = seqno;
	return 0;
}

static bool
gen6_ring_get_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	if (!dev->irq_enabled)
	       return false;

	/* It looks like we need to prevent the gt from suspending while waiting
	 * for an notifiy irq, otherwise irqs seem to get lost on at least the
	 * blt/bsd rings on ivb. */
	gen6_gt_force_wake_get(dev_priv);

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (ring->irq_refcount++ == 0) {
		I915_WRITE_IMR(ring, ~ring->irq_enable_mask);
		dev_priv->gt_irq_mask &= ~ring->irq_enable_mask;
		I915_WRITE(GTIMR, dev_priv->gt_irq_mask);
		POSTING_READ(GTIMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

	return true;
}

static void
gen6_ring_put_irq(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	drm_i915_private_t *dev_priv = dev->dev_private;
	unsigned long flags;

	spin_lock_irqsave(&dev_priv->irq_lock, flags);
	if (--ring->irq_refcount == 0) {
		I915_WRITE_IMR(ring, ~0);
		dev_priv->gt_irq_mask |= ring->irq_enable_mask;
		I915_WRITE(GTIMR, dev_priv->gt_irq_mask);
		POSTING_READ(GTIMR);
	}
	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

	gen6_gt_force_wake_put(dev_priv);
}

static int
i965_dispatch_execbuffer(struct intel_ring_buffer *ring, u32 offset, u32 length)
{
	int ret;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring,
			MI_BATCH_BUFFER_START |
			MI_BATCH_GTT |
			MI_BATCH_NON_SECURE_I965);
	intel_ring_emit(ring, offset);
	intel_ring_advance(ring);

	return 0;
}

static int
i830_dispatch_execbuffer(struct intel_ring_buffer *ring,
				u32 offset, u32 len)
{
	int ret;

	ret = intel_ring_begin(ring, 4);
	if (ret)
		return ret;

	intel_ring_emit(ring, MI_BATCH_BUFFER);
	intel_ring_emit(ring, offset | MI_BATCH_NON_SECURE);
	intel_ring_emit(ring, offset + len - 8);
	intel_ring_emit(ring, 0);
	intel_ring_advance(ring);

	return 0;
}

static int
i915_dispatch_execbuffer(struct intel_ring_buffer *ring,
				u32 offset, u32 len)
{
	int ret;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring, MI_BATCH_BUFFER_START | MI_BATCH_GTT);
	intel_ring_emit(ring, offset | MI_BATCH_NON_SECURE);
	intel_ring_advance(ring);

	return 0;
}

static void cleanup_status_page(struct intel_ring_buffer *ring)
{
	struct drm_i915_gem_object *obj;

	obj = ring->status_page.obj;
	if (obj == NULL)
		return;

	kunmap(obj->pages[0]);
	i915_gem_object_unpin(obj);
	drm_gem_object_unreference(&obj->base);
	ring->status_page.obj = NULL;
}

static int init_status_page(struct intel_ring_buffer *ring)
{
	struct drm_device *dev = ring->dev;
	struct drm_i915_gem_object *obj;
	int ret;

	obj = i915_gem_alloc_object(dev, 4096);
	if (obj == NULL) {
		DRM_ERROR("Failed to allocate status page\n");
		ret = -ENOMEM;
		goto err;
	}

	i915_gem_object_set_cache_level(obj, I915_CACHE_LLC);

	ret = i915_gem_object_pin(obj, 4096, true);
	if (ret != 0) {
		goto err_unref;
	}

	ring->status_page.gfx_addr = obj->gtt_offset;
	ring->status_page.page_addr = kmap(obj->pages[0]);
	if (ring->status_page.page_addr == NULL) {
		goto err_unpin;
	}
	ring->status_page.obj = obj;
	memset(ring->status_page.page_addr, 0, PAGE_SIZE);

	intel_ring_setup_status_page(ring);
	DRM_DEBUG_DRIVER("%s hws offset: 0x%08x\n",
			ring->name, ring->status_page.gfx_addr);

	return 0;

err_unpin:
	i915_gem_object_unpin(obj);
err_unref:
	drm_gem_object_unreference(&obj->base);
err:
	return ret;
}

static int intel_init_ring_buffer(struct drm_device *dev,
				  struct intel_ring_buffer *ring)
{
	struct drm_i915_gem_object *obj;
	int ret;

	ring->dev = dev;
	INIT_LIST_HEAD(&ring->active_list);
	INIT_LIST_HEAD(&ring->request_list);
	INIT_LIST_HEAD(&ring->gpu_write_list);
	ring->size = 32 * PAGE_SIZE;

	init_waitqueue_head(&ring->irq_queue);

	if (I915_NEED_GFX_HWS(dev)) {
		ret = init_status_page(ring);
		if (ret)
			return ret;
	}

	obj = i915_gem_alloc_object(dev, ring->size);
	if (obj == NULL) {
		DRM_ERROR("Failed to allocate ringbuffer\n");
		ret = -ENOMEM;
		goto err_hws;
	}

	ring->obj = obj;

	ret = i915_gem_object_pin(obj, PAGE_SIZE, true);
	if (ret)
		goto err_unref;

	ring->virtual_start = ioremap_wc(dev->agp->base + obj->gtt_offset,
					 ring->size);
	if (ring->virtual_start == NULL) {
		DRM_ERROR("Failed to map ringbuffer.\n");
		ret = -EINVAL;
		goto err_unpin;
	}

	ret = ring->init(ring);
	if (ret)
		goto err_unmap;

	/* Workaround an erratum on the i830 which causes a hang if
	 * the TAIL pointer points to within the last 2 cachelines
	 * of the buffer.
	 */
	ring->effective_size = ring->size;
	if (IS_I830(ring->dev) || IS_845G(ring->dev))
		ring->effective_size -= 128;

	return 0;

err_unmap:
	iounmap(ring->virtual_start);
err_unpin:
	i915_gem_object_unpin(obj);
err_unref:
	drm_gem_object_unreference(&obj->base);
	ring->obj = NULL;
err_hws:
	cleanup_status_page(ring);
	return ret;
}

void intel_cleanup_ring_buffer(struct intel_ring_buffer *ring)
{
	struct drm_i915_private *dev_priv;
	int ret;

	if (ring->obj == NULL)
		return;

	/* Disable the ring buffer. The ring must be idle at this point */
	dev_priv = ring->dev->dev_private;
	ret = intel_wait_ring_idle(ring);
	if (ret)
		DRM_ERROR("failed to quiesce %s whilst cleaning up: %d\n",
			  ring->name, ret);

	I915_WRITE_CTL(ring, 0);

	iounmap(ring->virtual_start);

	i915_gem_object_unpin(ring->obj);
	drm_gem_object_unreference(&ring->obj->base);
	ring->obj = NULL;

	if (ring->cleanup)
		ring->cleanup(ring);

	cleanup_status_page(ring);
}

static int intel_wrap_ring_buffer(struct intel_ring_buffer *ring)
{
	uint32_t __iomem *virt;
	int rem = ring->size - ring->tail;

	if (ring->space < rem) {
		int ret = intel_wait_ring_buffer(ring, rem);
		if (ret)
			return ret;
	}

	virt = ring->virtual_start + ring->tail;
	rem /= 4;
	while (rem--)
		iowrite32(MI_NOOP, virt++);

	ring->tail = 0;
	ring->space = ring_space(ring);

	return 0;
}

static int intel_ring_wait_seqno(struct intel_ring_buffer *ring, u32 seqno)
{
	struct drm_i915_private *dev_priv = ring->dev->dev_private;
	bool was_interruptible;
	int ret;

	/* XXX As we have not yet audited all the paths to check that
	 * they are ready for ERESTARTSYS from intel_ring_begin, do not
	 * allow us to be interruptible by a signal.
	 */
	was_interruptible = dev_priv->mm.interruptible;
	dev_priv->mm.interruptible = false;

	ret = i915_wait_request(ring, seqno);

	dev_priv->mm.interruptible = was_interruptible;
	if (!ret)
		i915_gem_retire_requests_ring(ring);

	return ret;
}

static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
{
	struct drm_i915_gem_request *request;
	u32 seqno = 0;
	int ret;

	i915_gem_retire_requests_ring(ring);

	if (ring->last_retired_head != -1) {
		ring->head = ring->last_retired_head;
		ring->last_retired_head = -1;
		ring->space = ring_space(ring);
		if (ring->space >= n)
			return 0;
	}

	list_for_each_entry(request, &ring->request_list, list) {
		int space;

		if (request->tail == -1)
			continue;

		space = request->tail - (ring->tail + 8);
		if (space < 0)
			space += ring->size;
		if (space >= n) {
			seqno = request->seqno;
			break;
		}

		/* Consume this request in case we need more space than
		 * is available and so need to prevent a race between
		 * updating last_retired_head and direct reads of
		 * I915_RING_HEAD. It also provides a nice sanity check.
		 */
		request->tail = -1;
	}

	if (seqno == 0)
		return -ENOSPC;

	ret = intel_ring_wait_seqno(ring, seqno);
	if (ret)
		return ret;

	if (WARN_ON(ring->last_retired_head == -1))
		return -ENOSPC;

	ring->head = ring->last_retired_head;
	ring->last_retired_head = -1;
	ring->space = ring_space(ring);
	if (WARN_ON(ring->space < n))
		return -ENOSPC;

	return 0;
}

int intel_wait_ring_buffer(struct intel_ring_buffer *ring, int n)
{
	struct drm_device *dev = ring->dev;
	struct drm_i915_private *dev_priv = dev->dev_private;
	unsigned long end;
	int ret;

	ret = intel_ring_wait_request(ring, n);
	if (ret != -ENOSPC)
		return ret;

	trace_i915_ring_wait_begin(ring);
	/* With GEM the hangcheck timer should kick us out of the loop,
	 * leaving it early runs the risk of corrupting GEM state (due
	 * to running on almost untested codepaths). But on resume
	 * timers don't work yet, so prevent a complete hang in that
	 * case by choosing an insanely large timeout. */
	end = jiffies + 60 * HZ;

	do {
		ring->head = I915_READ_HEAD(ring);
		ring->space = ring_space(ring);
		if (ring->space >= n) {
			trace_i915_ring_wait_end(ring);
			return 0;
		}

		if (dev->primary->master) {
			struct drm_i915_master_private *master_priv = dev->primary->master->driver_priv;
			if (master_priv->sarea_priv)
				master_priv->sarea_priv->perf_boxes |= I915_BOX_WAIT;
		}

		msleep(1);
		if (atomic_read(&dev_priv->mm.wedged))
			return -EAGAIN;
	} while (!time_after(jiffies, end));
	trace_i915_ring_wait_end(ring);
	return -EBUSY;
}

int intel_ring_begin(struct intel_ring_buffer *ring,
		     int num_dwords)
{
	struct drm_i915_private *dev_priv = ring->dev->dev_private;
	int n = 4*num_dwords;
	int ret;

	if (unlikely(atomic_read(&dev_priv->mm.wedged)))
		return -EIO;

	if (unlikely(ring->tail + n > ring->effective_size)) {
		ret = intel_wrap_ring_buffer(ring);
		if (unlikely(ret))
			return ret;
	}

	if (unlikely(ring->space < n)) {
		ret = intel_wait_ring_buffer(ring, n);
		if (unlikely(ret))
			return ret;
	}

	ring->space -= n;
	return 0;
}

void intel_ring_advance(struct intel_ring_buffer *ring)
{
	struct drm_i915_private *dev_priv = ring->dev->dev_private;

	ring->tail &= ring->size - 1;
	if (dev_priv->stop_rings & intel_ring_flag(ring))
		return;
	ring->write_tail(ring, ring->tail);
}


static void gen6_bsd_ring_write_tail(struct intel_ring_buffer *ring,
				     u32 value)
{
	drm_i915_private_t *dev_priv = ring->dev->dev_private;

       /* Every tail move must follow the sequence below */
	I915_WRITE(GEN6_BSD_SLEEP_PSMI_CONTROL,
		GEN6_BSD_SLEEP_PSMI_CONTROL_RC_ILDL_MESSAGE_MODIFY_MASK |
		GEN6_BSD_SLEEP_PSMI_CONTROL_RC_ILDL_MESSAGE_DISABLE);
	I915_WRITE(GEN6_BSD_RNCID, 0x0);

	if (wait_for((I915_READ(GEN6_BSD_SLEEP_PSMI_CONTROL) &
		GEN6_BSD_SLEEP_PSMI_CONTROL_IDLE_INDICATOR) == 0,
		50))
	DRM_ERROR("timed out waiting for IDLE Indicator\n");

	I915_WRITE_TAIL(ring, value);
	I915_WRITE(GEN6_BSD_SLEEP_PSMI_CONTROL,
		GEN6_BSD_SLEEP_PSMI_CONTROL_RC_ILDL_MESSAGE_MODIFY_MASK |
		GEN6_BSD_SLEEP_PSMI_CONTROL_RC_ILDL_MESSAGE_ENABLE);
}

static int gen6_ring_flush(struct intel_ring_buffer *ring,
			   u32 invalidate, u32 flush)
{
	uint32_t cmd;
	int ret;

	ret = intel_ring_begin(ring, 4);
	if (ret)
		return ret;

	cmd = MI_FLUSH_DW;
	if (invalidate & I915_GEM_GPU_DOMAINS)
		cmd |= MI_INVALIDATE_TLB | MI_INVALIDATE_BSD;
	intel_ring_emit(ring, cmd);
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);
	return 0;
}

static int
gen6_ring_dispatch_execbuffer(struct intel_ring_buffer *ring,
			      u32 offset, u32 len)
{
	int ret;

	ret = intel_ring_begin(ring, 2);
	if (ret)
		return ret;

	intel_ring_emit(ring, MI_BATCH_BUFFER_START | MI_BATCH_NON_SECURE_I965);
	/* bit0-7 is the length on GEN6+ */
	intel_ring_emit(ring, offset);
	intel_ring_advance(ring);

	return 0;
}

/* Blitter support (SandyBridge+) */

static int blt_ring_flush(struct intel_ring_buffer *ring,
			  u32 invalidate, u32 flush)
{
	uint32_t cmd;
	int ret;

	ret = intel_ring_begin(ring, 4);
	if (ret)
		return ret;

	cmd = MI_FLUSH_DW;
	if (invalidate & I915_GEM_DOMAIN_RENDER)
		cmd |= MI_INVALIDATE_TLB;
	intel_ring_emit(ring, cmd);
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, 0);
	intel_ring_emit(ring, MI_NOOP);
	intel_ring_advance(ring);
	return 0;
}

int intel_init_render_ring_buffer(struct drm_device *dev)
{
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct intel_ring_buffer *ring = &dev_priv->ring[RCS];

	ring->name = "render ring";
	ring->id = RCS;
	ring->mmio_base = RENDER_RING_BASE;

	if (INTEL_INFO(dev)->gen >= 6) {
		ring->add_request = gen6_add_request;
		ring->flush = gen6_render_ring_flush;
		ring->irq_get = gen6_ring_get_irq;
		ring->irq_put = gen6_ring_put_irq;
		ring->irq_enable_mask = GT_USER_INTERRUPT;
		ring->get_seqno = gen6_ring_get_seqno;
		ring->sync_to = gen6_ring_sync;
		ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_INVALID;
		ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_RV;
		ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_RB;
		ring->signal_mbox[0] = GEN6_VRSYNC;
		ring->signal_mbox[1] = GEN6_BRSYNC;
	} else if (IS_GEN5(dev)) {
		ring->add_request = pc_render_add_request;
		ring->flush = gen4_render_ring_flush;
		ring->get_seqno = pc_render_get_seqno;
		ring->irq_get = gen5_ring_get_irq;
		ring->irq_put = gen5_ring_put_irq;
		ring->irq_enable_mask = GT_USER_INTERRUPT | GT_PIPE_NOTIFY;
	} else {
		ring->add_request = i9xx_add_request;
		if (INTEL_INFO(dev)->gen < 4)
			ring->flush = gen2_render_ring_flush;
		else
			ring->flush = gen4_render_ring_flush;
		ring->get_seqno = ring_get_seqno;
		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 >= 6)
		ring->dispatch_execbuffer = gen6_ring_dispatch_execbuffer;
	else if (INTEL_INFO(dev)->gen >= 4)
		ring->dispatch_execbuffer = i965_dispatch_execbuffer;
	else if (IS_I830(dev) || IS_845G(dev))
		ring->dispatch_execbuffer = i830_dispatch_execbuffer;
	else
		ring->dispatch_execbuffer = i915_dispatch_execbuffer;
	ring->init = init_render_ring;
	ring->cleanup = render_ring_cleanup;


	if (!I915_NEED_GFX_HWS(dev)) {
		ring->status_page.page_addr = dev_priv->status_page_dmah->vaddr;
		memset(ring->status_page.page_addr, 0, PAGE_SIZE);
	}

	return intel_init_ring_buffer(dev, ring);
}

int intel_render_ring_init_dri(struct drm_device *dev, u64 start, u32 size)
{
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct intel_ring_buffer *ring = &dev_priv->ring[RCS];

	ring->name = "render ring";
	ring->id = RCS;
	ring->mmio_base = RENDER_RING_BASE;

	if (INTEL_INFO(dev)->gen >= 6) {
		/* non-kms not supported on gen6+ */
		return -ENODEV;
	}

	/* Note: gem is not supported on gen5/ilk without kms (the corresponding
	 * gem_init ioctl returns with -ENODEV). Hence we do not need to set up
	 * the special gen5 functions. */
	ring->add_request = i9xx_add_request;
	if (INTEL_INFO(dev)->gen < 4)
		ring->flush = gen2_render_ring_flush;
	else
		ring->flush = gen4_render_ring_flush;
	ring->get_seqno = ring_get_seqno;
	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)
		ring->dispatch_execbuffer = i965_dispatch_execbuffer;
	else if (IS_I830(dev) || IS_845G(dev))
		ring->dispatch_execbuffer = i830_dispatch_execbuffer;
	else
		ring->dispatch_execbuffer = i915_dispatch_execbuffer;
	ring->init = init_render_ring;
	ring->cleanup = render_ring_cleanup;

	if (!I915_NEED_GFX_HWS(dev))
		ring->status_page.page_addr = dev_priv->status_page_dmah->vaddr;

	ring->dev = dev;
	INIT_LIST_HEAD(&ring->active_list);
	INIT_LIST_HEAD(&ring->request_list);
	INIT_LIST_HEAD(&ring->gpu_write_list);

	ring->size = size;
	ring->effective_size = ring->size;
	if (IS_I830(ring->dev))
		ring->effective_size -= 128;

	ring->virtual_start = ioremap_wc(start, size);
	if (ring->virtual_start == NULL) {
		DRM_ERROR("can not ioremap virtual address for"
			  " ring buffer\n");
		return -ENOMEM;
	}

	return 0;
}

int intel_init_bsd_ring_buffer(struct drm_device *dev)
{
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct intel_ring_buffer *ring = &dev_priv->ring[VCS];

	ring->name = "bsd ring";
	ring->id = VCS;

	ring->write_tail = ring_write_tail;
	if (IS_GEN6(dev) || IS_GEN7(dev)) {
		ring->mmio_base = GEN6_BSD_RING_BASE;
		/* gen6 bsd needs a special wa for tail updates */
		if (IS_GEN6(dev))
			ring->write_tail = gen6_bsd_ring_write_tail;
		ring->flush = gen6_ring_flush;
		ring->add_request = gen6_add_request;
		ring->get_seqno = gen6_ring_get_seqno;
		ring->irq_enable_mask = GEN6_BSD_USER_INTERRUPT;
		ring->irq_get = gen6_ring_get_irq;
		ring->irq_put = gen6_ring_put_irq;
		ring->dispatch_execbuffer = gen6_ring_dispatch_execbuffer;
		ring->sync_to = gen6_ring_sync;
		ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_VR;
		ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_INVALID;
		ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_VB;
		ring->signal_mbox[0] = GEN6_RVSYNC;
		ring->signal_mbox[1] = GEN6_BVSYNC;
	} else {
		ring->mmio_base = BSD_RING_BASE;
		ring->flush = bsd_ring_flush;
		ring->add_request = i9xx_add_request;
		ring->get_seqno = ring_get_seqno;
		if (IS_GEN5(dev)) {
			ring->irq_enable_mask = GT_BSD_USER_INTERRUPT;
			ring->irq_get = gen5_ring_get_irq;
			ring->irq_put = gen5_ring_put_irq;
		} else {
			ring->irq_enable_mask = I915_BSD_USER_INTERRUPT;
			ring->irq_get = i9xx_ring_get_irq;
			ring->irq_put = i9xx_ring_put_irq;
		}
		ring->dispatch_execbuffer = i965_dispatch_execbuffer;
	}
	ring->init = init_ring_common;


	return intel_init_ring_buffer(dev, ring);
}

int intel_init_blt_ring_buffer(struct drm_device *dev)
{
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct intel_ring_buffer *ring = &dev_priv->ring[BCS];

	ring->name = "blitter ring";
	ring->id = BCS;

	ring->mmio_base = BLT_RING_BASE;
	ring->write_tail = ring_write_tail;
	ring->flush = blt_ring_flush;
	ring->add_request = gen6_add_request;
	ring->get_seqno = gen6_ring_get_seqno;
	ring->irq_enable_mask = GEN6_BLITTER_USER_INTERRUPT;
	ring->irq_get = gen6_ring_get_irq;
	ring->irq_put = gen6_ring_put_irq;
	ring->dispatch_execbuffer = gen6_ring_dispatch_execbuffer;
	ring->sync_to = gen6_ring_sync;
	ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_BR;
	ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_BV;
	ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_INVALID;
	ring->signal_mbox[0] = GEN6_RBSYNC;
	ring->signal_mbox[1] = GEN6_VBSYNC;
	ring->init = init_ring_common;

	return intel_init_ring_buffer(dev, ring);
}