drivers/gpu/drm/i915/i915_guc_submission.c

/*
 * Copyright © 2014 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.
 *
 */
#include <linux/circ_buf.h>
#include "i915_drv.h"
#include "intel_uc.h"

#include <trace/events/dma_fence.h>

/**
 * DOC: GuC-based command submission
 *
 * GuC client:
 * A i915_guc_client refers to a submission path through GuC. Currently, there
 * is only one of these (the execbuf_client) and this one is charged with all
 * submissions to the GuC. This struct is the owner of a doorbell, a process
 * descriptor and a workqueue (all of them inside a single gem object that
 * contains all required pages for these elements).
 *
 * GuC context descriptor:
 * During initialization, the driver allocates a static pool of 1024 such
 * descriptors, and shares them with the GuC.
 * Currently, there exists a 1:1 mapping between a i915_guc_client and a
 * guc_context_desc (via the client's context_index), so effectively only
 * one guc_context_desc gets used. This context descriptor lets the GuC know
 * about the doorbell, workqueue and process descriptor. Theoretically, it also
 * lets the GuC know about our HW contexts (Context ID, etc...), but we actually
 * employ a kind of submission where the GuC uses the LRCA sent via the work
 * item instead (the single guc_context_desc associated to execbuf client
 * contains information about the default kernel context only, but this is
 * essentially unused). This is called a "proxy" submission.
 *
 * The Scratch registers:
 * There are 16 MMIO-based registers start from 0xC180. The kernel driver writes
 * a value to the action register (SOFT_SCRATCH_0) along with any data. It then
 * triggers an interrupt on the GuC via another register write (0xC4C8).
 * Firmware writes a success/fail code back to the action register after
 * processes the request. The kernel driver polls waiting for this update and
 * then proceeds.
 * See intel_guc_send()
 *
 * Doorbells:
 * Doorbells are interrupts to uKernel. A doorbell is a single cache line (QW)
 * mapped into process space.
 *
 * Work Items:
 * There are several types of work items that the host may place into a
 * workqueue, each with its own requirements and limitations. Currently only
 * WQ_TYPE_INORDER is needed to support legacy submission via GuC, which
 * represents in-order queue. The kernel driver packs ring tail pointer and an
 * ELSP context descriptor dword into Work Item.
 * See guc_wq_item_append()
 *
 * ADS:
 * The Additional Data Struct (ADS) has pointers for different buffers used by
 * the GuC. One single gem object contains the ADS struct itself (guc_ads), the
 * scheduling policies (guc_policies), a structure describing a collection of
 * register sets (guc_mmio_reg_state) and some extra pages for the GuC to save
 * its internal state for sleep.
 *
 */

static inline bool is_high_priority(struct i915_guc_client* client)
{
	return client->priority <= GUC_CTX_PRIORITY_HIGH;
}

static int __reserve_doorbell(struct i915_guc_client *client)
{
	unsigned long offset;
	unsigned long end;
	u16 id;

	GEM_BUG_ON(client->doorbell_id != GUC_DOORBELL_INVALID);

	/*
	 * The bitmap tracks which doorbell registers are currently in use.
	 * It is split into two halves; the first half is used for normal
	 * priority contexts, the second half for high-priority ones.
	 */
	offset = 0;
	end = GUC_NUM_DOORBELLS/2;
	if (is_high_priority(client)) {
		offset = end;
		end += offset;
	}

	id = find_next_zero_bit(client->guc->doorbell_bitmap, offset, end);
	if (id == end)
		return -ENOSPC;

	__set_bit(id, client->guc->doorbell_bitmap);
	client->doorbell_id = id;
	DRM_DEBUG_DRIVER("client %u (high prio=%s) reserved doorbell: %d\n",
			 client->ctx_index, yesno(is_high_priority(client)),
			 id);
	return 0;
}

static void __unreserve_doorbell(struct i915_guc_client *client)
{
	GEM_BUG_ON(client->doorbell_id == GUC_DOORBELL_INVALID);

	__clear_bit(client->doorbell_id, client->guc->doorbell_bitmap);
	client->doorbell_id = GUC_DOORBELL_INVALID;
}

/*
 * Tell the GuC to allocate or deallocate a specific doorbell
 */

static int __guc_allocate_doorbell(struct intel_guc *guc, u32 ctx_index)
{
	u32 action[] = {
		INTEL_GUC_ACTION_ALLOCATE_DOORBELL,
		ctx_index
	};

	return intel_guc_send(guc, action, ARRAY_SIZE(action));
}

static int __guc_deallocate_doorbell(struct intel_guc *guc, u32 ctx_index)
{
	u32 action[] = {
		INTEL_GUC_ACTION_DEALLOCATE_DOORBELL,
		ctx_index
	};

	return intel_guc_send(guc, action, ARRAY_SIZE(action));
}

static struct guc_context_desc *__get_context_desc(struct i915_guc_client *client)
{
	struct guc_context_desc *base = client->guc->ctx_pool_vaddr;

	return &base[client->ctx_index];
}

/*
 * Initialise, update, or clear doorbell data shared with the GuC
 *
 * These functions modify shared data and so need access to the mapped
 * client object which contains the page being used for the doorbell
 */

static int __update_doorbell_desc(struct i915_guc_client *client, u16 new_id)
{
	struct guc_context_desc *desc;

	/* Update the GuC's idea of the doorbell ID */
	desc = __get_context_desc(client);
	desc->db_id = new_id;

	return 0;
}

static struct guc_doorbell_info *__get_doorbell(struct i915_guc_client *client)
{
	return client->vaddr + client->doorbell_offset;
}

static bool has_doorbell(struct i915_guc_client *client)
{
	if (client->doorbell_id == GUC_DOORBELL_INVALID)
		return false;

	return test_bit(client->doorbell_id, client->guc->doorbell_bitmap);
}

static int __create_doorbell(struct i915_guc_client *client)
{
	struct guc_doorbell_info *doorbell;
	int err;

	doorbell = __get_doorbell(client);
	doorbell->db_status = GUC_DOORBELL_ENABLED;
	doorbell->cookie = client->doorbell_cookie;

	err = __guc_allocate_doorbell(client->guc, client->ctx_index);
	if (err) {
		doorbell->db_status = GUC_DOORBELL_DISABLED;
		doorbell->cookie = 0;
	}
	return err;
}

static int __destroy_doorbell(struct i915_guc_client *client)
{
	struct drm_i915_private *dev_priv = guc_to_i915(client->guc);
	struct guc_doorbell_info *doorbell;
	u16 db_id = client->doorbell_id;

	GEM_BUG_ON(db_id >= GUC_DOORBELL_INVALID);

	doorbell = __get_doorbell(client);
	doorbell->db_status = GUC_DOORBELL_DISABLED;
	doorbell->cookie = 0;

	/* Doorbell release flow requires that we wait for GEN8_DRB_VALID bit
	 * to go to zero after updating db_status before we call the GuC to
	 * release the doorbell */
	if (wait_for_us(!(I915_READ(GEN8_DRBREGL(db_id)) & GEN8_DRB_VALID), 10))
		WARN_ONCE(true, "Doorbell never became invalid after disable\n");

	return __guc_deallocate_doorbell(client->guc, client->ctx_index);
}

static int destroy_doorbell(struct i915_guc_client *client)
{
	int err;

	GEM_BUG_ON(!has_doorbell(client));

	/* XXX: wait for any interrupts */
	/* XXX: wait for workqueue to drain */

	err = __destroy_doorbell(client);
	if (err)
		return err;

	__update_doorbell_desc(client, GUC_DOORBELL_INVALID);

	__unreserve_doorbell(client);

	return 0;
}

static unsigned long __select_cacheline(struct intel_guc* guc)
{
	unsigned long offset;

	/* Doorbell uses a single cache line within a page */
	offset = offset_in_page(guc->db_cacheline);

	/* Moving to next cache line to reduce contention */
	guc->db_cacheline += cache_line_size();

	DRM_DEBUG_DRIVER("reserved cacheline 0x%lx, next 0x%x, linesize %u\n",
			offset, guc->db_cacheline, cache_line_size());
	return offset;
}

/*
 * Initialise the process descriptor shared with the GuC firmware.
 */
static void guc_proc_desc_init(struct intel_guc *guc,
			       struct i915_guc_client *client)
{
	struct guc_process_desc *desc;

	desc = client->vaddr + client->proc_desc_offset;

	memset(desc, 0, sizeof(*desc));

	/*
	 * XXX: pDoorbell and WQVBaseAddress are pointers in process address
	 * space for ring3 clients (set them as in mmap_ioctl) or kernel
	 * space for kernel clients (map on demand instead? May make debug
	 * easier to have it mapped).
	 */
	desc->wq_base_addr = 0;
	desc->db_base_addr = 0;

	desc->context_id = client->ctx_index;
	desc->wq_size_bytes = client->wq_size;
	desc->wq_status = WQ_STATUS_ACTIVE;
	desc->priority = client->priority;
}

/*
 * Initialise/clear the context descriptor shared with the GuC firmware.
 *
 * This descriptor tells the GuC where (in GGTT space) to find the important
 * data structures relating to this client (doorbell, process descriptor,
 * write queue, etc).
 */
static void guc_ctx_desc_init(struct intel_guc *guc,
			      struct i915_guc_client *client)
{
	struct drm_i915_private *dev_priv = guc_to_i915(guc);
	struct intel_engine_cs *engine;
	struct i915_gem_context *ctx = client->owner;
	struct guc_context_desc *desc;
	unsigned int tmp;
	u32 gfx_addr;

	desc = __get_context_desc(client);
	memset(desc, 0, sizeof(*desc));

	desc->attribute = GUC_CTX_DESC_ATTR_ACTIVE | GUC_CTX_DESC_ATTR_KERNEL;
	desc->context_id = client->ctx_index;
	desc->priority = client->priority;
	desc->db_id = client->doorbell_id;

	for_each_engine_masked(engine, dev_priv, client->engines, tmp) {
		struct intel_context *ce = &ctx->engine[engine->id];
		uint32_t guc_engine_id = engine->guc_id;
		struct guc_execlist_context *lrc = &desc->lrc[guc_engine_id];

		/* TODO: We have a design issue to be solved here. Only when we
		 * receive the first batch, we know which engine is used by the
		 * user. But here GuC expects the lrc and ring to be pinned. It
		 * is not an issue for default context, which is the only one
		 * for now who owns a GuC client. But for future owner of GuC
		 * client, need to make sure lrc is pinned prior to enter here.
		 */
		if (!ce->state)
			break;	/* XXX: continue? */

		/*
		 * XXX: When this is a GUC_CTX_DESC_ATTR_KERNEL client (proxy
		 * submission or, in other words, not using a direct submission
		 * model) the KMD's LRCA is not used for any work submission.
		 * Instead, the GuC uses the LRCA of the user mode context (see
		 * guc_wq_item_append below).
		 */
		lrc->context_desc = lower_32_bits(ce->lrc_desc);

		/* The state page is after PPHWSP */
		lrc->ring_lrca =
			guc_ggtt_offset(ce->state) + LRC_STATE_PN * PAGE_SIZE;
		lrc->context_id = (client->ctx_index << GUC_ELC_CTXID_OFFSET) |
				(guc_engine_id << GUC_ELC_ENGINE_OFFSET);

		lrc->ring_begin = guc_ggtt_offset(ce->ring->vma);
		lrc->ring_end = lrc->ring_begin + ce->ring->size - 1;
		lrc->ring_next_free_location = lrc->ring_begin;
		lrc->ring_current_tail_pointer_value = 0;

		desc->engines_used |= (1 << guc_engine_id);
	}

	DRM_DEBUG_DRIVER("Host engines 0x%x => GuC engines used 0x%x\n",
			client->engines, desc->engines_used);
	WARN_ON(desc->engines_used == 0);

	/*
	 * The doorbell, process descriptor, and workqueue are all parts
	 * of the client object, which the GuC will reference via the GGTT
	 */
	gfx_addr = guc_ggtt_offset(client->vma);
	desc->db_trigger_phy = sg_dma_address(client->vma->pages->sgl) +
				client->doorbell_offset;
	desc->db_trigger_cpu = (uintptr_t)__get_doorbell(client);
	desc->db_trigger_uk = gfx_addr + client->doorbell_offset;
	desc->process_desc = gfx_addr + client->proc_desc_offset;
	desc->wq_addr = gfx_addr + client->wq_offset;
	desc->wq_size = client->wq_size;

	desc->desc_private = (uintptr_t)client;
}

static void guc_ctx_desc_fini(struct intel_guc *guc,
			      struct i915_guc_client *client)
{
	struct guc_context_desc *desc;

	desc = __get_context_desc(client);
	memset(desc, 0, sizeof(*desc));
}

/**
 * i915_guc_wq_reserve() - reserve space in the GuC's workqueue
 * @request:	request associated with the commands
 *
 * Return:	0 if space is available
 *		-EAGAIN if space is not currently available
 *
 * This function must be called (and must return 0) before a request
 * is submitted to the GuC via i915_guc_submit() below. Once a result
 * of 0 has been returned, it must be balanced by a corresponding
 * call to submit().
 *
 * Reservation allows the caller to determine in advance that space
 * will be available for the next submission before committing resources
 * to it, and helps avoid late failures with complicated recovery paths.
 */
int i915_guc_wq_reserve(struct drm_i915_gem_request *request)
{
	const size_t wqi_size = sizeof(struct guc_wq_item);
	struct i915_guc_client *client = request->i915->guc.execbuf_client;
	struct guc_process_desc *desc = client->vaddr +
					client->proc_desc_offset;
	u32 freespace;
	int ret;

	spin_lock_irq(&client->wq_lock);
	freespace = CIRC_SPACE(client->wq_tail, desc->head, client->wq_size);
	freespace -= client->wq_rsvd;
	if (likely(freespace >= wqi_size)) {
		client->wq_rsvd += wqi_size;
		ret = 0;
	} else {
		client->no_wq_space++;
		ret = -EAGAIN;
	}
	spin_unlock_irq(&client->wq_lock);

	return ret;
}

static void guc_client_update_wq_rsvd(struct i915_guc_client *client, int size)
{
	unsigned long flags;

	spin_lock_irqsave(&client->wq_lock, flags);
	client->wq_rsvd += size;
	spin_unlock_irqrestore(&client->wq_lock, flags);
}

void i915_guc_wq_unreserve(struct drm_i915_gem_request *request)
{
	const int wqi_size = sizeof(struct guc_wq_item);
	struct i915_guc_client *client = request->i915->guc.execbuf_client;

	GEM_BUG_ON(READ_ONCE(client->wq_rsvd) < wqi_size);
	guc_client_update_wq_rsvd(client, -wqi_size);
}

/* Construct a Work Item and append it to the GuC's Work Queue */
static void guc_wq_item_append(struct i915_guc_client *client,
			       struct drm_i915_gem_request *rq)
{
	/* wqi_len is in DWords, and does not include the one-word header */
	const size_t wqi_size = sizeof(struct guc_wq_item);
	const u32 wqi_len = wqi_size/sizeof(u32) - 1;
	struct intel_engine_cs *engine = rq->engine;
	struct guc_process_desc *desc;
	struct guc_wq_item *wqi;
	u32 freespace, tail, wq_off;

	desc = client->vaddr + client->proc_desc_offset;

	/* Free space is guaranteed, see i915_guc_wq_reserve() above */
	freespace = CIRC_SPACE(client->wq_tail, desc->head, client->wq_size);
	GEM_BUG_ON(freespace < wqi_size);

	/* The GuC firmware wants the tail index in QWords, not bytes */
	tail = rq->tail;
	GEM_BUG_ON(tail & 7);
	tail >>= 3;
	GEM_BUG_ON(tail > WQ_RING_TAIL_MAX);

	/* For now workqueue item is 4 DWs; workqueue buffer is 2 pages. So we
	 * should not have the case where structure wqi is across page, neither
	 * wrapped to the beginning. This simplifies the implementation below.
	 *
	 * XXX: if not the case, we need save data to a temp wqi and copy it to
	 * workqueue buffer dw by dw.
	 */
	BUILD_BUG_ON(wqi_size != 16);
	GEM_BUG_ON(client->wq_rsvd < wqi_size);

	/* postincrement WQ tail for next time */
	wq_off = client->wq_tail;
	GEM_BUG_ON(wq_off & (wqi_size - 1));
	client->wq_tail += wqi_size;
	client->wq_tail &= client->wq_size - 1;
	client->wq_rsvd -= wqi_size;

	/* WQ starts from the page after doorbell / process_desc */
	wqi = client->vaddr + wq_off + GUC_DB_SIZE;

	/* Now fill in the 4-word work queue item */
	wqi->header = WQ_TYPE_INORDER |
			(wqi_len << WQ_LEN_SHIFT) |
			(engine->guc_id << WQ_TARGET_SHIFT) |
			WQ_NO_WCFLUSH_WAIT;

	/* The GuC wants only the low-order word of the context descriptor */
	wqi->context_desc = (u32)intel_lr_context_descriptor(rq->ctx, engine);

	wqi->submit_element_info = tail << WQ_RING_TAIL_SHIFT;
	wqi->fence_id = rq->global_seqno;
}

static int guc_ring_doorbell(struct i915_guc_client *client)
{
	struct guc_process_desc *desc;
	union guc_doorbell_qw db_cmp, db_exc, db_ret;
	union guc_doorbell_qw *db;
	int attempt = 2, ret = -EAGAIN;

	desc = client->vaddr + client->proc_desc_offset;

	/* Update the tail so it is visible to GuC */
	desc->tail = client->wq_tail;

	/* current cookie */
	db_cmp.db_status = GUC_DOORBELL_ENABLED;
	db_cmp.cookie = client->doorbell_cookie;

	/* cookie to be updated */
	db_exc.db_status = GUC_DOORBELL_ENABLED;
	db_exc.cookie = client->doorbell_cookie + 1;
	if (db_exc.cookie == 0)
		db_exc.cookie = 1;

	/* pointer of current doorbell cacheline */
	db = (union guc_doorbell_qw *)__get_doorbell(client);

	while (attempt--) {
		/* lets ring the doorbell */
		db_ret.value_qw = atomic64_cmpxchg((atomic64_t *)db,
			db_cmp.value_qw, db_exc.value_qw);

		/* if the exchange was successfully executed */
		if (db_ret.value_qw == db_cmp.value_qw) {
			/* db was successfully rung */
			client->doorbell_cookie = db_exc.cookie;
			ret = 0;
			break;
		}

		/* XXX: doorbell was lost and need to acquire it again */
		if (db_ret.db_status == GUC_DOORBELL_DISABLED)
			break;

		DRM_WARN("Cookie mismatch. Expected %d, found %d\n",
			 db_cmp.cookie, db_ret.cookie);

		/* update the cookie to newly read cookie from GuC */
		db_cmp.cookie = db_ret.cookie;
		db_exc.cookie = db_ret.cookie + 1;
		if (db_exc.cookie == 0)
			db_exc.cookie = 1;
	}

	return ret;
}

/**
 * __i915_guc_submit() - Submit commands through GuC
 * @rq:		request associated with the commands
 *
 * The caller must have already called i915_guc_wq_reserve() above with
 * a result of 0 (success), guaranteeing that there is space in the work
 * queue for the new request, so enqueuing the item cannot fail.
 *
 * Bad Things Will Happen if the caller violates this protocol e.g. calls
 * submit() when _reserve() says there's no space, or calls _submit()
 * a different number of times from (successful) calls to _reserve().
 *
 * The only error here arises if the doorbell hardware isn't functioning
 * as expected, which really shouln't happen.
 */
static void __i915_guc_submit(struct drm_i915_gem_request *rq)
{
	struct drm_i915_private *dev_priv = rq->i915;
	struct intel_engine_cs *engine = rq->engine;
	unsigned int engine_id = engine->id;
	struct intel_guc *guc = &rq->i915->guc;
	struct i915_guc_client *client = guc->execbuf_client;
	unsigned long flags;
	int b_ret;

	/* WA to flush out the pending GMADR writes to ring buffer. */
	if (i915_vma_is_map_and_fenceable(rq->ring->vma))
		POSTING_READ_FW(GUC_STATUS);

	spin_lock_irqsave(&client->wq_lock, flags);

	guc_wq_item_append(client, rq);
	b_ret = guc_ring_doorbell(client);

	client->submissions[engine_id] += 1;
	client->retcode = b_ret;
	if (b_ret)
		client->b_fail += 1;

	guc->submissions[engine_id] += 1;
	guc->last_seqno[engine_id] = rq->global_seqno;

	spin_unlock_irqrestore(&client->wq_lock, flags);
}

static void i915_guc_submit(struct drm_i915_gem_request *rq)
{
	__i915_gem_request_submit(rq);
	__i915_guc_submit(rq);
}

static void nested_enable_signaling(struct drm_i915_gem_request *rq)
{
	/* If we use dma_fence_enable_sw_signaling() directly, lockdep
	 * detects an ordering issue between the fence lockclass and the
	 * global_timeline. This circular dependency can only occur via 2
	 * different fences (but same fence lockclass), so we use the nesting
	 * annotation here to prevent the warn, equivalent to the nesting
	 * inside i915_gem_request_submit() for when we also enable the
	 * signaler.
	 */

	if (test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
			     &rq->fence.flags))
		return;

	GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags));
	trace_dma_fence_enable_signal(&rq->fence);

	spin_lock_nested(&rq->lock, SINGLE_DEPTH_NESTING);
	intel_engine_enable_signaling(rq);
	spin_unlock(&rq->lock);
}

static bool i915_guc_dequeue(struct intel_engine_cs *engine)
{
	struct execlist_port *port = engine->execlist_port;
	struct drm_i915_gem_request *last = port[0].request;
	struct rb_node *rb;
	bool submit = false;

	/* After execlist_first is updated, the tasklet will be rescheduled.
	 *
	 * If we are currently running (inside the tasklet) and a third
	 * party queues a request and so updates engine->execlist_first under
	 * the spinlock (which we have elided), it will atomically set the
	 * TASKLET_SCHED flag causing the us to be re-executed and pick up
	 * the change in state (the update to TASKLET_SCHED incurs a memory
	 * barrier making this cross-cpu checking safe).
	 */
	if (!READ_ONCE(engine->execlist_first))
		return false;

	spin_lock_irq(&engine->timeline->lock);
	rb = engine->execlist_first;
	while (rb) {
		struct drm_i915_gem_request *rq =
			rb_entry(rb, typeof(*rq), priotree.node);

		if (last && rq->ctx != last->ctx) {
			if (port != engine->execlist_port)
				break;

			i915_gem_request_assign(&port->request, last);
			nested_enable_signaling(last);
			port++;
		}

		rb = rb_next(rb);
		rb_erase(&rq->priotree.node, &engine->execlist_queue);
		RB_CLEAR_NODE(&rq->priotree.node);
		rq->priotree.priority = INT_MAX;

		i915_guc_submit(rq);
		trace_i915_gem_request_in(rq, port - engine->execlist_port);
		last = rq;
		submit = true;
	}
	if (submit) {
		i915_gem_request_assign(&port->request, last);
		nested_enable_signaling(last);
		engine->execlist_first = rb;
	}
	spin_unlock_irq(&engine->timeline->lock);

	return submit;
}

static void i915_guc_irq_handler(unsigned long data)
{
	struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
	struct execlist_port *port = engine->execlist_port;
	struct drm_i915_gem_request *rq;
	bool submit;

	do {
		rq = port[0].request;
		while (rq && i915_gem_request_completed(rq)) {
			trace_i915_gem_request_out(rq);
			i915_gem_request_put(rq);
			port[0].request = port[1].request;
			port[1].request = NULL;
			rq = port[0].request;
		}

		submit = false;
		if (!port[1].request)
			submit = i915_guc_dequeue(engine);
	} while (submit);
}

/*
 * Everything below here is concerned with setup & teardown, and is
 * therefore not part of the somewhat time-critical batch-submission
 * path of i915_guc_submit() above.
 */

/**
 * intel_guc_allocate_vma() - Allocate a GGTT VMA for GuC usage
 * @guc:	the guc
 * @size:	size of area to allocate (both virtual space and memory)
 *
 * This is a wrapper to create an object for use with the GuC. In order to
 * use it inside the GuC, an object needs to be pinned lifetime, so we allocate
 * both some backing storage and a range inside the Global GTT. We must pin
 * it in the GGTT somewhere other than than [0, GUC_WOPCM_TOP) because that
 * range is reserved inside GuC.
 *
 * Return:	A i915_vma if successful, otherwise an ERR_PTR.
 */
struct i915_vma *intel_guc_allocate_vma(struct intel_guc *guc, u32 size)
{
	struct drm_i915_private *dev_priv = guc_to_i915(guc);
	struct drm_i915_gem_object *obj;
	struct i915_vma *vma;
	int ret;

	obj = i915_gem_object_create(dev_priv, size);
	if (IS_ERR(obj))
		return ERR_CAST(obj);

	vma = i915_vma_instance(obj, &dev_priv->ggtt.base, NULL);
	if (IS_ERR(vma))
		goto err;

	ret = i915_vma_pin(vma, 0, PAGE_SIZE,
			   PIN_GLOBAL | PIN_OFFSET_BIAS | GUC_WOPCM_TOP);
	if (ret) {
		vma = ERR_PTR(ret);
		goto err;
	}

	return vma;

err:
	i915_gem_object_put(obj);
	return vma;
}

static void guc_client_free(struct i915_guc_client *client)
{
	/*
	 * XXX: wait for any outstanding submissions before freeing memory.
	 * Be sure to drop any locks
	 */
	guc_ctx_desc_fini(client->guc, client);
	i915_gem_object_unpin_map(client->vma->obj);
	i915_vma_unpin_and_release(&client->vma);
	ida_simple_remove(&client->guc->ctx_ids, client->ctx_index);
	kfree(client);
}

/* Check that a doorbell register is in the expected state */
static bool doorbell_ok(struct intel_guc *guc, u16 db_id)
{
	struct drm_i915_private *dev_priv = guc_to_i915(guc);
	u32 drbregl;
	bool valid;

	GEM_BUG_ON(db_id >= GUC_DOORBELL_INVALID);

	drbregl = I915_READ(GEN8_DRBREGL(db_id));
	valid = drbregl & GEN8_DRB_VALID;

	if (test_bit(db_id, guc->doorbell_bitmap) == valid)
		return true;

	DRM_DEBUG_DRIVER("Doorbell %d has unexpected state (0x%x): valid=%s\n",
			 db_id, drbregl, yesno(valid));

	return false;
}

/*
 * If the GuC thinks that the doorbell is unassigned (e.g. because we reset and
 * reloaded the GuC FW) we can use this function to tell the GuC to reassign the
 * doorbell to the rightful owner.
 */
static int __reset_doorbell(struct i915_guc_client* client, u16 db_id)
{
	int err;

	err = __update_doorbell_desc(client, db_id);
	if (!err)
		err = __create_doorbell(client);
	if (!err)
		err = __destroy_doorbell(client);

	return err;
}

/*
 * Borrow the first client to set up & tear down each unused doorbell
 * in turn, to ensure that all doorbell h/w is (re)initialised.
 */
static int guc_init_doorbell_hw(struct intel_guc *guc)
{
	struct i915_guc_client *client = guc->execbuf_client;
	int err;
	int i;

	if (has_doorbell(client))
		destroy_doorbell(client);

	for (i = 0; i < GUC_NUM_DOORBELLS; ++i) {
		if (doorbell_ok(guc, i))
			continue;

		err = __reset_doorbell(client, i);
		WARN(err, "Doorbell %d reset failed, err %d\n", i, err);
	}

	/* Read back & verify all doorbell registers */
	for (i = 0; i < GUC_NUM_DOORBELLS; ++i)
		WARN_ON(!doorbell_ok(guc, i));

	err = __reserve_doorbell(client);
	if (err)
		return err;

	err = __update_doorbell_desc(client, client->doorbell_id);
	if (err)
		goto err_reserve;

	err = __create_doorbell(client);
	if (err)
		goto err_update;

	return 0;
err_reserve:
	__unreserve_doorbell(client);
err_update:
	__update_doorbell_desc(client, GUC_DOORBELL_INVALID);
	return err;
}

/**
 * guc_client_alloc() - Allocate an i915_guc_client
 * @dev_priv:	driver private data structure
 * @engines:	The set of engines to enable for this client
 * @priority:	four levels priority _CRITICAL, _HIGH, _NORMAL and _LOW
 * 		The kernel client to replace ExecList submission is created with
 * 		NORMAL priority. Priority of a client for scheduler can be HIGH,
 * 		while a preemption context can use CRITICAL.
 * @ctx:	the context that owns the client (we use the default render
 * 		context)
 *
 * Return:	An i915_guc_client object if success, else NULL.
 */
static struct i915_guc_client *
guc_client_alloc(struct drm_i915_private *dev_priv,
		 uint32_t engines,
		 uint32_t priority,
		 struct i915_gem_context *ctx)
{
	struct i915_guc_client *client;
	struct intel_guc *guc = &dev_priv->guc;
	struct i915_vma *vma;
	void *vaddr;
	int ret;

	client = kzalloc(sizeof(*client), GFP_KERNEL);
	if (!client)
		return ERR_PTR(-ENOMEM);

	client->guc = guc;
	client->owner = ctx;
	client->engines = engines;
	client->priority = priority;
	client->doorbell_id = GUC_DOORBELL_INVALID;
	client->wq_offset = GUC_DB_SIZE;
	client->wq_size = GUC_WQ_SIZE;
	spin_lock_init(&client->wq_lock);

	ret = ida_simple_get(&guc->ctx_ids, 0, GUC_MAX_GPU_CONTEXTS,
				GFP_KERNEL);
	if (ret < 0)
		goto err_client;

	client->ctx_index = ret;

	/* The first page is doorbell/proc_desc. Two followed pages are wq. */
	vma = intel_guc_allocate_vma(guc, GUC_DB_SIZE + GUC_WQ_SIZE);
	if (IS_ERR(vma)) {
		ret = PTR_ERR(vma);
		goto err_id;
	}

	/* We'll keep just the first (doorbell/proc) page permanently kmap'd. */
	client->vma = vma;

	vaddr = i915_gem_object_pin_map(vma->obj, I915_MAP_WB);
	if (IS_ERR(vaddr)) {
		ret = PTR_ERR(vaddr);
		goto err_vma;
	}
	client->vaddr = vaddr;

	client->doorbell_offset = __select_cacheline(guc);

	/*
	 * Since the doorbell only requires a single cacheline, we can save
	 * space by putting the application process descriptor in the same
	 * page. Use the half of the page that doesn't include the doorbell.
	 */
	if (client->doorbell_offset >= (GUC_DB_SIZE / 2))
		client->proc_desc_offset = 0;
	else
		client->proc_desc_offset = (GUC_DB_SIZE / 2);

	guc_proc_desc_init(guc, client);
	guc_ctx_desc_init(guc, client);

	/* FIXME: Runtime client allocation (which currently we don't do) will
	 * require that the doorbell gets created now. The static execbuf_client
	 * is now getting its doorbell later (on submission enable) but maybe we
	 * also want to reorder things in the future so that we don't have to
	 * special case the doorbell creation */

	DRM_DEBUG_DRIVER("new priority %u client %p for engine(s) 0x%x: ctx_index %u\n",
			 priority, client, client->engines, client->ctx_index);
	DRM_DEBUG_DRIVER("doorbell id %u, cacheline offset 0x%lx\n",
			 client->doorbell_id, client->doorbell_offset);

	return client;
err_vma:
	i915_vma_unpin_and_release(&client->vma);
err_id:
	ida_simple_remove(&guc->ctx_ids, client->ctx_index);
err_client:
	kfree(client);
	return ERR_PTR(ret);
}

static void guc_policies_init(struct guc_policies *policies)
{
	struct guc_policy *policy;
	u32 p, i;

	policies->dpc_promote_time = 500000;
	policies->max_num_work_items = POLICY_MAX_NUM_WI;

	for (p = 0; p < GUC_CTX_PRIORITY_NUM; p++) {
		for (i = GUC_RENDER_ENGINE; i < GUC_MAX_ENGINES_NUM; i++) {
			policy = &policies->policy[p][i];

			policy->execution_quantum = 1000000;
			policy->preemption_time = 500000;
			policy->fault_time = 250000;
			policy->policy_flags = 0;
		}
	}

	policies->is_valid = 1;
}

static int guc_ads_create(struct intel_guc *guc)
{
	struct drm_i915_private *dev_priv = guc_to_i915(guc);
	struct i915_vma *vma;
	struct page *page;
	/* The ads obj includes the struct itself and buffers passed to GuC */
	struct {
		struct guc_ads ads;
		struct guc_policies policies;
		struct guc_mmio_reg_state reg_state;
		u8 reg_state_buffer[GUC_S3_SAVE_SPACE_PAGES * PAGE_SIZE];
	} __packed *blob;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	u32 base;

	GEM_BUG_ON(guc->ads_vma);

	vma = intel_guc_allocate_vma(guc, PAGE_ALIGN(sizeof(*blob)));
	if (IS_ERR(vma))
		return PTR_ERR(vma);

	guc->ads_vma = vma;

	page = i915_vma_first_page(vma);
	blob = kmap(page);

	/* GuC scheduling policies */
	guc_policies_init(&blob->policies);

	/* MMIO reg state */
	for_each_engine(engine, dev_priv, id) {
		blob->reg_state.mmio_white_list[engine->guc_id].mmio_start =
			engine->mmio_base + GUC_MMIO_WHITE_LIST_START;

		/* Nothing to be saved or restored for now. */
		blob->reg_state.mmio_white_list[engine->guc_id].count = 0;
	}

	/*
	 * The GuC requires a "Golden Context" when it reinitialises
	 * engines after a reset. Here we use the Render ring default
	 * context, which must already exist and be pinned in the GGTT,
	 * so its address won't change after we've told the GuC where
	 * to find it.
	 */
	blob->ads.golden_context_lrca =
		dev_priv->engine[RCS]->status_page.ggtt_offset;

	for_each_engine(engine, dev_priv, id)
		blob->ads.eng_state_size[engine->guc_id] =
			intel_lr_context_size(engine);

	base = guc_ggtt_offset(vma);
	blob->ads.scheduler_policies = base + ptr_offset(blob, policies);
	blob->ads.reg_state_buffer = base + ptr_offset(blob, reg_state_buffer);
	blob->ads.reg_state_addr = base + ptr_offset(blob, reg_state);

	kunmap(page);

	return 0;
}

static void guc_ads_destroy(struct intel_guc *guc)
{
	i915_vma_unpin_and_release(&guc->ads_vma);
}

/*
 * Set up the memory resources to be shared with the GuC.  At this point,
 * we require just one object that can be mapped through the GGTT.
 */
int i915_guc_submission_init(struct drm_i915_private *dev_priv)
{
	const size_t ctxsize = sizeof(struct guc_context_desc);
	const size_t poolsize = GUC_MAX_GPU_CONTEXTS * ctxsize;
	const size_t gemsize = round_up(poolsize, PAGE_SIZE);
	struct intel_guc *guc = &dev_priv->guc;
	struct i915_vma *vma;
	void *vaddr;
	int ret;

	if (!HAS_GUC_SCHED(dev_priv))
		return 0;

	/* Wipe bitmap & delete client in case of reinitialisation */
	bitmap_clear(guc->doorbell_bitmap, 0, GUC_NUM_DOORBELLS);
	i915_guc_submission_disable(dev_priv);

	if (!i915.enable_guc_submission)
		return 0;

	if (guc->ctx_pool)
		return 0;

	vma = intel_guc_allocate_vma(guc, gemsize);
	if (IS_ERR(vma))
		return PTR_ERR(vma);

	guc->ctx_pool = vma;

	vaddr = i915_gem_object_pin_map(guc->ctx_pool->obj, I915_MAP_WB);
	if (IS_ERR(vaddr)) {
		ret = PTR_ERR(vaddr);
		goto err_vma;
	}

	guc->ctx_pool_vaddr = vaddr;

	ret = intel_guc_log_create(guc);
	if (ret < 0)
		goto err_vaddr;

	ret = guc_ads_create(guc);
	if (ret < 0)
		goto err_log;

	ida_init(&guc->ctx_ids);

	guc->execbuf_client = guc_client_alloc(dev_priv,
					       INTEL_INFO(dev_priv)->ring_mask,
					       GUC_CTX_PRIORITY_KMD_NORMAL,
					       dev_priv->kernel_context);
	if (IS_ERR(guc->execbuf_client)) {
		DRM_ERROR("Failed to create GuC client for execbuf!\n");
		ret = PTR_ERR(guc->execbuf_client);
		goto err_ads;
	}

	return 0;

err_ads:
	guc_ads_destroy(guc);
err_log:
	intel_guc_log_destroy(guc);
err_vaddr:
	i915_gem_object_unpin_map(guc->ctx_pool->obj);
err_vma:
	i915_vma_unpin_and_release(&guc->ctx_pool);
	return ret;
}

void i915_guc_submission_fini(struct drm_i915_private *dev_priv)
{
	struct intel_guc *guc = &dev_priv->guc;

	if (!i915.enable_guc_submission)
		return 0;

	guc_client_free(guc->execbuf_client);
	guc->execbuf_client = NULL;
	ida_destroy(&guc->ctx_ids);
	guc_ads_destroy(guc);
	intel_guc_log_destroy(guc);
	i915_gem_object_unpin_map(guc->ctx_pool->obj);
	i915_vma_unpin_and_release(&guc->ctx_pool);
}

static void guc_reset_wq(struct i915_guc_client *client)
{
	struct guc_process_desc *desc = client->vaddr +
					client->proc_desc_offset;

	desc->head = 0;
	desc->tail = 0;

	client->wq_tail = 0;
}

static void guc_interrupts_capture(struct drm_i915_private *dev_priv)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int irqs;

	/* tell all command streamers to forward interrupts (but not vblank) to GuC */
	irqs = _MASKED_BIT_ENABLE(GFX_INTERRUPT_STEERING);
	for_each_engine(engine, dev_priv, id)
		I915_WRITE(RING_MODE_GEN7(engine), irqs);

	/* route USER_INTERRUPT to Host, all others are sent to GuC. */
	irqs = GT_RENDER_USER_INTERRUPT << GEN8_RCS_IRQ_SHIFT |
	       GT_RENDER_USER_INTERRUPT << GEN8_BCS_IRQ_SHIFT;
	/* These three registers have the same bit definitions */
	I915_WRITE(GUC_BCS_RCS_IER, ~irqs);
	I915_WRITE(GUC_VCS2_VCS1_IER, ~irqs);
	I915_WRITE(GUC_WD_VECS_IER, ~irqs);

	/*
	 * The REDIRECT_TO_GUC bit of the PMINTRMSK register directs all
	 * (unmasked) PM interrupts to the GuC. All other bits of this
	 * register *disable* generation of a specific interrupt.
	 *
	 * 'pm_intrmsk_mbz' indicates bits that are NOT to be set when
	 * writing to the PM interrupt mask register, i.e. interrupts
	 * that must not be disabled.
	 *
	 * If the GuC is handling these interrupts, then we must not let
	 * the PM code disable ANY interrupt that the GuC is expecting.
	 * So for each ENABLED (0) bit in this register, we must SET the
	 * bit in pm_intrmsk_mbz so that it's left enabled for the GuC.
	 * GuC needs ARAT expired interrupt unmasked hence it is set in
	 * pm_intrmsk_mbz.
	 *
	 * Here we CLEAR REDIRECT_TO_GUC bit in pm_intrmsk_mbz, which will
	 * result in the register bit being left SET!
	 */
	dev_priv->rps.pm_intrmsk_mbz |= ARAT_EXPIRED_INTRMSK;
	dev_priv->rps.pm_intrmsk_mbz &= ~GEN8_PMINTR_DISABLE_REDIRECT_TO_GUC;
}

int i915_guc_submission_enable(struct drm_i915_private *dev_priv)
{
	struct intel_guc *guc = &dev_priv->guc;
	struct i915_guc_client *client = guc->execbuf_client;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int err;

	if (!client)
		return -ENODEV;

	err = intel_guc_sample_forcewake(guc);
	if (err)
		return err;

	guc_reset_wq(client);
	err = guc_init_doorbell_hw(guc);
	if (err)
		return err;

	/* Take over from manual control of ELSP (execlists) */
	guc_interrupts_capture(dev_priv);

	for_each_engine(engine, dev_priv, id) {
		const int wqi_size = sizeof(struct guc_wq_item);
		struct drm_i915_gem_request *rq;

		/* The tasklet was initialised by execlists, and may be in
		 * a state of flux (across a reset) and so we just want to
		 * take over the callback without changing any other state
		 * in the tasklet.
		 */
		engine->irq_tasklet.func = i915_guc_irq_handler;
		clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);

		/* Replay the current set of previously submitted requests */
		spin_lock_irq(&engine->timeline->lock);
		list_for_each_entry(rq, &engine->timeline->requests, link) {
			guc_client_update_wq_rsvd(client, wqi_size);
			__i915_guc_submit(rq);
		}
		spin_unlock_irq(&engine->timeline->lock);
	}

	return 0;
}

static void guc_interrupts_release(struct drm_i915_private *dev_priv)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int irqs;

	/*
	 * tell all command streamers NOT to forward interrupts or vblank
	 * to GuC.
	 */
	irqs = _MASKED_FIELD(GFX_FORWARD_VBLANK_MASK, GFX_FORWARD_VBLANK_NEVER);
	irqs |= _MASKED_BIT_DISABLE(GFX_INTERRUPT_STEERING);
	for_each_engine(engine, dev_priv, id)
		I915_WRITE(RING_MODE_GEN7(engine), irqs);

	/* route all GT interrupts to the host */
	I915_WRITE(GUC_BCS_RCS_IER, 0);
	I915_WRITE(GUC_VCS2_VCS1_IER, 0);
	I915_WRITE(GUC_WD_VECS_IER, 0);

	dev_priv->rps.pm_intrmsk_mbz |= GEN8_PMINTR_DISABLE_REDIRECT_TO_GUC;
	dev_priv->rps.pm_intrmsk_mbz &= ~ARAT_EXPIRED_INTRMSK;
}

void i915_guc_submission_disable(struct drm_i915_private *dev_priv)
{
	struct intel_guc *guc = &dev_priv->guc;

	guc_interrupts_release(dev_priv);

	if (!guc->execbuf_client)
		return;

	/* FIXME: in many cases, by the time we get here the GuC has been
	 * reset, so we cannot destroy the doorbell properly. Ignore the
	 * error message for now */
	destroy_doorbell(guc->execbuf_client);

	/* Revert back to manual ELSP submission */
	intel_engines_reset_default_submission(dev_priv);
}

/**
 * intel_guc_suspend() - notify GuC entering suspend state
 * @dev_priv:	i915 device private
 */
int intel_guc_suspend(struct drm_i915_private *dev_priv)
{
	struct intel_guc *guc = &dev_priv->guc;
	struct i915_gem_context *ctx;
	u32 data[3];

	if (guc->fw.load_status != INTEL_UC_FIRMWARE_SUCCESS)
		return 0;

	gen9_disable_guc_interrupts(dev_priv);

	ctx = dev_priv->kernel_context;

	data[0] = INTEL_GUC_ACTION_ENTER_S_STATE;
	/* any value greater than GUC_POWER_D0 */
	data[1] = GUC_POWER_D1;
	/* first page is shared data with GuC */
	data[2] = guc_ggtt_offset(ctx->engine[RCS].state);

	return intel_guc_send(guc, data, ARRAY_SIZE(data));
}


/**
 * intel_guc_resume() - notify GuC resuming from suspend state
 * @dev_priv:	i915 device private
 */
int intel_guc_resume(struct drm_i915_private *dev_priv)
{
	struct intel_guc *guc = &dev_priv->guc;
	struct i915_gem_context *ctx;
	u32 data[3];

	if (guc->fw.load_status != INTEL_UC_FIRMWARE_SUCCESS)
		return 0;

	if (i915.guc_log_level >= 0)
		gen9_enable_guc_interrupts(dev_priv);

	ctx = dev_priv->kernel_context;

	data[0] = INTEL_GUC_ACTION_EXIT_S_STATE;
	data[1] = GUC_POWER_D0;
	/* first page is shared data with GuC */
	data[2] = guc_ggtt_offset(ctx->engine[RCS].state);

	return intel_guc_send(guc, data, ARRAY_SIZE(data));
}