// SPDX-License-Identifier: MIT
/*
 * Copyright © 2014 Intel Corporation
 */

#include <linux/circ_buf.h>

#include "gem/i915_gem_context.h"

#include "gt/intel_context.h"
#include "gt/intel_engine_pm.h"
#include "gt/intel_gt.h"
#include "gt/intel_gt_pm.h"
#include "gt/intel_lrc_reg.h"
#include "intel_guc_submission.h"

#include "i915_drv.h"
#include "i915_trace.h"

enum {
	GUC_PREEMPT_NONE = 0,
	GUC_PREEMPT_INPROGRESS,
	GUC_PREEMPT_FINISHED,
};
#define GUC_PREEMPT_BREADCRUMB_DWORDS	0x8
#define GUC_PREEMPT_BREADCRUMB_BYTES	\
	(sizeof(u32) * GUC_PREEMPT_BREADCRUMB_DWORDS)

/**
 * DOC: GuC-based command submission
 *
 * IMPORTANT NOTE: GuC submission is currently not supported in i915. The GuC
 * firmware is moving to an updated submission interface and we plan to
 * turn submission back on when that lands. The below documentation (and related
 * code) matches the old submission model and will be updated as part of the
 * upgrade to the new flow.
 *
 * GuC client:
 * A intel_guc_client refers to a submission path through GuC. Currently, there
 * is only one client, which 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 stage 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 intel_guc_client and a
 * guc_stage_desc (via the client's stage_id), so effectively only one
 * gets used. This stage 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_stage_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_add_request()
 *
 */

static inline struct i915_priolist *to_priolist(struct rb_node *rb)
{
	return rb_entry(rb, struct i915_priolist, node);
}

static inline bool is_high_priority(struct intel_guc_client *client)
{
	return (client->priority == GUC_CLIENT_PRIORITY_KMD_HIGH ||
		client->priority == GUC_CLIENT_PRIORITY_HIGH);
}

static int reserve_doorbell(struct intel_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, end, offset);
	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->stage_id, yesno(is_high_priority(client)),
			 id);
	return 0;
}

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

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

static void unreserve_doorbell(struct intel_guc_client *client)
{
	GEM_BUG_ON(!has_doorbell(client));

	__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 stage_id)
{
	u32 action[] = {
		INTEL_GUC_ACTION_ALLOCATE_DOORBELL,
		stage_id
	};

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

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

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

static struct guc_stage_desc *__get_stage_desc(struct intel_guc_client *client)
{
	struct guc_stage_desc *base = client->guc->stage_desc_pool_vaddr;

	return &base[client->stage_id];
}

/*
 * 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 void __update_doorbell_desc(struct intel_guc_client *client, u16 new_id)
{
	struct guc_stage_desc *desc;

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

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

static bool __doorbell_valid(struct intel_guc *guc, u16 db_id)
{
	struct intel_uncore *uncore = guc_to_gt(guc)->uncore;

	GEM_BUG_ON(db_id >= GUC_NUM_DOORBELLS);
	return intel_uncore_read(uncore, GEN8_DRBREGL(db_id)) & GEN8_DRB_VALID;
}

static void __init_doorbell(struct intel_guc_client *client)
{
	struct guc_doorbell_info *doorbell;

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

static void __fini_doorbell(struct intel_guc_client *client)
{
	struct guc_doorbell_info *doorbell;
	u16 db_id = client->doorbell_id;

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

	/* 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(!__doorbell_valid(client->guc, db_id), 10))
		WARN_ONCE(true, "Doorbell never became invalid after disable\n");
}

static int create_doorbell(struct intel_guc_client *client)
{
	int ret;

	if (WARN_ON(!has_doorbell(client)))
		return -ENODEV; /* internal setup error, should never happen */

	__update_doorbell_desc(client, client->doorbell_id);
	__init_doorbell(client);

	ret = __guc_allocate_doorbell(client->guc, client->stage_id);
	if (ret) {
		__fini_doorbell(client);
		__update_doorbell_desc(client, GUC_DOORBELL_INVALID);
		DRM_DEBUG_DRIVER("Couldn't create client %u doorbell: %d\n",
				 client->stage_id, ret);
		return ret;
	}

	return 0;
}

static int destroy_doorbell(struct intel_guc_client *client)
{
	int ret;

	GEM_BUG_ON(!has_doorbell(client));

	__fini_doorbell(client);
	ret = __guc_deallocate_doorbell(client->guc, client->stage_id);
	if (ret)
		DRM_ERROR("Couldn't destroy client %u doorbell: %d\n",
			  client->stage_id, ret);

	__update_doorbell_desc(client, GUC_DOORBELL_INVALID);

	return ret;
}

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;
}

static inline struct guc_process_desc *
__get_process_desc(struct intel_guc_client *client)
{
	return client->vaddr + client->proc_desc_offset;
}

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

	desc = memset(__get_process_desc(client), 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->stage_id = client->stage_id;
	desc->wq_size_bytes = GUC_WQ_SIZE;
	desc->wq_status = WQ_STATUS_ACTIVE;
	desc->priority = client->priority;
}

static void guc_proc_desc_fini(struct intel_guc_client *client)
{
	struct guc_process_desc *desc;

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

static int guc_stage_desc_pool_create(struct intel_guc *guc)
{
	struct i915_vma *vma;
	void *vaddr;

	vma = intel_guc_allocate_vma(guc,
				     PAGE_ALIGN(sizeof(struct guc_stage_desc) *
				     GUC_MAX_STAGE_DESCRIPTORS));
	if (IS_ERR(vma))
		return PTR_ERR(vma);

	vaddr = i915_gem_object_pin_map(vma->obj, I915_MAP_WB);
	if (IS_ERR(vaddr)) {
		i915_vma_unpin_and_release(&vma, 0);
		return PTR_ERR(vaddr);
	}

	guc->stage_desc_pool = vma;
	guc->stage_desc_pool_vaddr = vaddr;
	ida_init(&guc->stage_ids);

	return 0;
}

static void guc_stage_desc_pool_destroy(struct intel_guc *guc)
{
	ida_destroy(&guc->stage_ids);
	i915_vma_unpin_and_release(&guc->stage_desc_pool, I915_VMA_RELEASE_MAP);
}

/*
 * Initialise/clear the stage 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_stage_desc_init(struct intel_guc_client *client)
{
	struct intel_guc *guc = client->guc;
	struct guc_stage_desc *desc;
	u32 gfx_addr;

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

	desc->attribute = GUC_STAGE_DESC_ATTR_ACTIVE |
			  GUC_STAGE_DESC_ATTR_KERNEL;
	if (is_high_priority(client))
		desc->attribute |= GUC_STAGE_DESC_ATTR_PREEMPT;
	desc->stage_id = client->stage_id;
	desc->priority = client->priority;
	desc->db_id = client->doorbell_id;

	/*
	 * The doorbell, process descriptor, and workqueue are all parts
	 * of the client object, which the GuC will reference via the GGTT
	 */
	gfx_addr = intel_guc_ggtt_offset(guc, client->vma);
	desc->db_trigger_phy = sg_dma_address(client->vma->pages->sgl) +
				client->doorbell_offset;
	desc->db_trigger_cpu = ptr_to_u64(__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 + GUC_DB_SIZE;
	desc->wq_size = GUC_WQ_SIZE;

	desc->desc_private = ptr_to_u64(client);
}

static void guc_stage_desc_fini(struct intel_guc_client *client)
{
	struct guc_stage_desc *desc;

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

/* Construct a Work Item and append it to the GuC's Work Queue */
static void guc_wq_item_append(struct intel_guc_client *client,
			       u32 target_engine, u32 context_desc,
			       u32 ring_tail, u32 fence_id)
{
	/* 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 guc_process_desc *desc = __get_process_desc(client);
	struct guc_wq_item *wqi;
	u32 wq_off;

	lockdep_assert_held(&client->wq_lock);

	/* 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);

	/* We expect the WQ to be active if we're appending items to it */
	GEM_BUG_ON(desc->wq_status != WQ_STATUS_ACTIVE);

	/* Free space is guaranteed. */
	wq_off = READ_ONCE(desc->tail);
	GEM_BUG_ON(CIRC_SPACE(wq_off, READ_ONCE(desc->head),
			      GUC_WQ_SIZE) < wqi_size);
	GEM_BUG_ON(wq_off & (wqi_size - 1));

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

	if (I915_SELFTEST_ONLY(client->use_nop_wqi)) {
		wqi->header = WQ_TYPE_NOOP | (wqi_len << WQ_LEN_SHIFT);
	} else {
		/* Now fill in the 4-word work queue item */
		wqi->header = WQ_TYPE_INORDER |
			      (wqi_len << WQ_LEN_SHIFT) |
			      (target_engine << WQ_TARGET_SHIFT) |
			      WQ_NO_WCFLUSH_WAIT;
		wqi->context_desc = context_desc;
		wqi->submit_element_info = ring_tail << WQ_RING_TAIL_SHIFT;
		GEM_BUG_ON(ring_tail > WQ_RING_TAIL_MAX);
		wqi->fence_id = fence_id;
	}

	/* Make the update visible to GuC */
	WRITE_ONCE(desc->tail, (wq_off + wqi_size) & (GUC_WQ_SIZE - 1));
}

static void guc_ring_doorbell(struct intel_guc_client *client)
{
	struct guc_doorbell_info *db;
	u32 cookie;

	lockdep_assert_held(&client->wq_lock);

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

	/*
	 * We're not expecting the doorbell cookie to change behind our back,
	 * we also need to treat 0 as a reserved value.
	 */
	cookie = READ_ONCE(db->cookie);
	WARN_ON_ONCE(xchg(&db->cookie, cookie + 1 ?: cookie + 2) != cookie);

	/* XXX: doorbell was lost and need to acquire it again */
	GEM_BUG_ON(db->db_status != GUC_DOORBELL_ENABLED);
}

static void guc_add_request(struct intel_guc *guc, struct i915_request *rq)
{
	struct intel_guc_client *client = guc->execbuf_client;
	struct intel_engine_cs *engine = rq->engine;
	u32 ctx_desc = lower_32_bits(rq->hw_context->lrc_desc);
	u32 ring_tail = intel_ring_set_tail(rq->ring, rq->tail) / sizeof(u64);

	guc_wq_item_append(client, engine->guc_id, ctx_desc,
			   ring_tail, rq->fence.seqno);
	guc_ring_doorbell(client);
}

/*
 * When we're doing submissions using regular execlists backend, writing to
 * ELSP from CPU side is enough to make sure that writes to ringbuffer pages
 * pinned in mappable aperture portion of GGTT are visible to command streamer.
 * Writes done by GuC on our behalf are not guaranteeing such ordering,
 * therefore, to ensure the flush, we're issuing a POSTING READ.
 */
static void flush_ggtt_writes(struct i915_vma *vma)
{
	struct drm_i915_private *i915 = vma->vm->i915;

	if (i915_vma_is_map_and_fenceable(vma))
		intel_uncore_posting_read_fw(&i915->uncore, GUC_STATUS);
}

static void guc_submit(struct intel_engine_cs *engine,
		       struct i915_request **out,
		       struct i915_request **end)
{
	struct intel_guc *guc = &engine->gt->uc.guc;
	struct intel_guc_client *client = guc->execbuf_client;

	spin_lock(&client->wq_lock);

	do {
		struct i915_request *rq = *out++;

		flush_ggtt_writes(rq->ring->vma);
		guc_add_request(guc, rq);
	} while (out != end);

	spin_unlock(&client->wq_lock);
}

static inline int rq_prio(const struct i915_request *rq)
{
	return rq->sched.attr.priority | __NO_PREEMPTION;
}

static struct i915_request *schedule_in(struct i915_request *rq, int idx)
{
	trace_i915_request_in(rq, idx);

	/*
	 * Currently we are not tracking the rq->context being inflight
	 * (ce->inflight = rq->engine). It is only used by the execlists
	 * backend at the moment, a similar counting strategy would be
	 * required if we generalise the inflight tracking.
	 */

	intel_gt_pm_get(rq->engine->gt);
	return i915_request_get(rq);
}

static void schedule_out(struct i915_request *rq)
{
	trace_i915_request_out(rq);

	intel_gt_pm_put(rq->engine->gt);
	i915_request_put(rq);
}

static void __guc_dequeue(struct intel_engine_cs *engine)
{
	struct intel_engine_execlists * const execlists = &engine->execlists;
	struct i915_request **first = execlists->inflight;
	struct i915_request ** const last_port = first + execlists->port_mask;
	struct i915_request *last = first[0];
	struct i915_request **port;
	bool submit = false;
	struct rb_node *rb;

	lockdep_assert_held(&engine->active.lock);

	if (last) {
		if (*++first)
			return;

		last = NULL;
	}

	/*
	 * We write directly into the execlists->inflight queue and don't use
	 * the execlists->pending queue, as we don't have a distinct switch
	 * event.
	 */
	port = first;
	while ((rb = rb_first_cached(&execlists->queue))) {
		struct i915_priolist *p = to_priolist(rb);
		struct i915_request *rq, *rn;
		int i;

		priolist_for_each_request_consume(rq, rn, p, i) {
			if (last && rq->hw_context != last->hw_context) {
				if (port == last_port)
					goto done;

				*port = schedule_in(last,
						    port - execlists->inflight);
				port++;
			}

			list_del_init(&rq->sched.link);
			__i915_request_submit(rq);
			submit = true;
			last = rq;
		}

		rb_erase_cached(&p->node, &execlists->queue);
		i915_priolist_free(p);
	}
done:
	execlists->queue_priority_hint =
		rb ? to_priolist(rb)->priority : INT_MIN;
	if (submit) {
		*port = schedule_in(last, port - execlists->inflight);
		*++port = NULL;
		guc_submit(engine, first, port);
	}
	execlists->active = execlists->inflight;
}

static void guc_submission_tasklet(unsigned long data)
{
	struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
	struct intel_engine_execlists * const execlists = &engine->execlists;
	struct i915_request **port, *rq;
	unsigned long flags;

	spin_lock_irqsave(&engine->active.lock, flags);

	for (port = execlists->inflight; (rq = *port); port++) {
		if (!i915_request_completed(rq))
			break;

		schedule_out(rq);
	}
	if (port != execlists->inflight) {
		int idx = port - execlists->inflight;
		int rem = ARRAY_SIZE(execlists->inflight) - idx;
		memmove(execlists->inflight, port, rem * sizeof(*port));
	}

	__guc_dequeue(engine);

	spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void guc_reset_prepare(struct intel_engine_cs *engine)
{
	struct intel_engine_execlists * const execlists = &engine->execlists;

	GEM_TRACE("%s\n", engine->name);

	/*
	 * Prevent request submission to the hardware until we have
	 * completed the reset in i915_gem_reset_finish(). If a request
	 * is completed by one engine, it may then queue a request
	 * to a second via its execlists->tasklet *just* as we are
	 * calling engine->init_hw() and also writing the ELSP.
	 * Turning off the execlists->tasklet until the reset is over
	 * prevents the race.
	 */
	__tasklet_disable_sync_once(&execlists->tasklet);
}

static void
cancel_port_requests(struct intel_engine_execlists * const execlists)
{
	struct i915_request * const *port, *rq;

	/* Note we are only using the inflight and not the pending queue */

	for (port = execlists->active; (rq = *port); port++)
		schedule_out(rq);
	execlists->active =
		memset(execlists->inflight, 0, sizeof(execlists->inflight));
}

static void guc_reset(struct intel_engine_cs *engine, bool stalled)
{
	struct intel_engine_execlists * const execlists = &engine->execlists;
	struct i915_request *rq;
	unsigned long flags;

	spin_lock_irqsave(&engine->active.lock, flags);

	cancel_port_requests(execlists);

	/* Push back any incomplete requests for replay after the reset. */
	rq = execlists_unwind_incomplete_requests(execlists);
	if (!rq)
		goto out_unlock;

	if (!i915_request_started(rq))
		stalled = false;

	__i915_request_reset(rq, stalled);
	intel_lr_context_reset(engine, rq->hw_context, rq->head, stalled);

out_unlock:
	spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void guc_cancel_requests(struct intel_engine_cs *engine)
{
	struct intel_engine_execlists * const execlists = &engine->execlists;
	struct i915_request *rq, *rn;
	struct rb_node *rb;
	unsigned long flags;

	GEM_TRACE("%s\n", engine->name);

	/*
	 * Before we call engine->cancel_requests(), we should have exclusive
	 * access to the submission state. This is arranged for us by the
	 * caller disabling the interrupt generation, the tasklet and other
	 * threads that may then access the same state, giving us a free hand
	 * to reset state. However, we still need to let lockdep be aware that
	 * we know this state may be accessed in hardirq context, so we
	 * disable the irq around this manipulation and we want to keep
	 * the spinlock focused on its duties and not accidentally conflate
	 * coverage to the submission's irq state. (Similarly, although we
	 * shouldn't need to disable irq around the manipulation of the
	 * submission's irq state, we also wish to remind ourselves that
	 * it is irq state.)
	 */
	spin_lock_irqsave(&engine->active.lock, flags);

	/* Cancel the requests on the HW and clear the ELSP tracker. */
	cancel_port_requests(execlists);

	/* Mark all executing requests as skipped. */
	list_for_each_entry(rq, &engine->active.requests, sched.link) {
		if (!i915_request_signaled(rq))
			dma_fence_set_error(&rq->fence, -EIO);

		i915_request_mark_complete(rq);
	}

	/* Flush the queued requests to the timeline list (for retiring). */
	while ((rb = rb_first_cached(&execlists->queue))) {
		struct i915_priolist *p = to_priolist(rb);
		int i;

		priolist_for_each_request_consume(rq, rn, p, i) {
			list_del_init(&rq->sched.link);
			__i915_request_submit(rq);
			dma_fence_set_error(&rq->fence, -EIO);
			i915_request_mark_complete(rq);
		}

		rb_erase_cached(&p->node, &execlists->queue);
		i915_priolist_free(p);
	}

	/* Remaining _unready_ requests will be nop'ed when submitted */

	execlists->queue_priority_hint = INT_MIN;
	execlists->queue = RB_ROOT_CACHED;

	spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void guc_reset_finish(struct intel_engine_cs *engine)
{
	struct intel_engine_execlists * const execlists = &engine->execlists;

	if (__tasklet_enable(&execlists->tasklet))
		/* And kick in case we missed a new request submission. */
		tasklet_hi_schedule(&execlists->tasklet);

	GEM_TRACE("%s: depth->%d\n", engine->name,
		  atomic_read(&execlists->tasklet.count));
}

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

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

	GEM_BUG_ON(db_id >= GUC_NUM_DOORBELLS);

	valid = __doorbell_valid(guc, db_id);

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

	DRM_DEBUG_DRIVER("Doorbell %u has unexpected state: valid=%s\n",
			 db_id, yesno(valid));

	return false;
}

static bool guc_verify_doorbells(struct intel_guc *guc)
{
	bool doorbells_ok = true;
	u16 db_id;

	for (db_id = 0; db_id < GUC_NUM_DOORBELLS; ++db_id)
		if (!doorbell_ok(guc, db_id))
			doorbells_ok = false;

	return doorbells_ok;
}

/**
 * guc_client_alloc() - Allocate an intel_guc_client
 * @guc:	the intel_guc structure
 * @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.
 *
 * Return:	An intel_guc_client object if success, else NULL.
 */
static struct intel_guc_client *
guc_client_alloc(struct intel_guc *guc, u32 priority)
{
	struct intel_guc_client *client;
	struct i915_vma *vma;
	void *vaddr;
	int ret;

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

	client->guc = guc;
	client->priority = priority;
	client->doorbell_id = GUC_DOORBELL_INVALID;
	spin_lock_init(&client->wq_lock);

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

	client->stage_id = 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;

	ret = reserve_doorbell(client);
	if (ret)
		goto err_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);

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

	return client;

err_vaddr:
	i915_gem_object_unpin_map(client->vma->obj);
err_vma:
	i915_vma_unpin_and_release(&client->vma, 0);
err_id:
	ida_simple_remove(&guc->stage_ids, client->stage_id);
err_client:
	kfree(client);
	return ERR_PTR(ret);
}

static void guc_client_free(struct intel_guc_client *client)
{
	unreserve_doorbell(client);
	i915_vma_unpin_and_release(&client->vma, I915_VMA_RELEASE_MAP);
	ida_simple_remove(&client->guc->stage_ids, client->stage_id);
	kfree(client);
}

static inline bool ctx_save_restore_disabled(struct intel_context *ce)
{
	u32 sr = ce->lrc_reg_state[CTX_CONTEXT_CONTROL + 1];

#define SR_DISABLED \
	_MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT | \
			   CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT)

	return (sr & SR_DISABLED) == SR_DISABLED;

#undef SR_DISABLED
}

static int guc_clients_create(struct intel_guc *guc)
{
	struct intel_guc_client *client;

	GEM_BUG_ON(guc->execbuf_client);

	client = guc_client_alloc(guc, GUC_CLIENT_PRIORITY_KMD_NORMAL);
	if (IS_ERR(client)) {
		DRM_ERROR("Failed to create GuC client for submission!\n");
		return PTR_ERR(client);
	}
	guc->execbuf_client = client;

	return 0;
}

static void guc_clients_destroy(struct intel_guc *guc)
{
	struct intel_guc_client *client;

	client = fetch_and_zero(&guc->execbuf_client);
	if (client)
		guc_client_free(client);
}

static int __guc_client_enable(struct intel_guc_client *client)
{
	int ret;

	guc_proc_desc_init(client);
	guc_stage_desc_init(client);

	ret = create_doorbell(client);
	if (ret)
		goto fail;

	return 0;

fail:
	guc_stage_desc_fini(client);
	guc_proc_desc_fini(client);
	return ret;
}

static void __guc_client_disable(struct intel_guc_client *client)
{
	/*
	 * By the time we're here, GuC may have already been reset. if that is
	 * the case, instead of trying (in vain) to communicate with it, let's
	 * just cleanup the doorbell HW and our internal state.
	 */
	if (intel_guc_is_running(client->guc))
		destroy_doorbell(client);
	else
		__fini_doorbell(client);

	guc_stage_desc_fini(client);
	guc_proc_desc_fini(client);
}

static int guc_clients_enable(struct intel_guc *guc)
{
	return __guc_client_enable(guc->execbuf_client);
}

static void guc_clients_disable(struct intel_guc *guc)
{
	if (guc->execbuf_client)
		__guc_client_disable(guc->execbuf_client);
}

/*
 * Set up the memory resources to be shared with the GuC (via the GGTT)
 * at firmware loading time.
 */
int intel_guc_submission_init(struct intel_guc *guc)
{
	int ret;

	if (guc->stage_desc_pool)
		return 0;

	ret = guc_stage_desc_pool_create(guc);
	if (ret)
		return ret;
	/*
	 * Keep static analysers happy, let them know that we allocated the
	 * vma after testing that it didn't exist earlier.
	 */
	GEM_BUG_ON(!guc->stage_desc_pool);

	WARN_ON(!guc_verify_doorbells(guc));
	ret = guc_clients_create(guc);
	if (ret)
		goto err_pool;

	return 0;

err_pool:
	guc_stage_desc_pool_destroy(guc);
	return ret;
}

void intel_guc_submission_fini(struct intel_guc *guc)
{
	guc_clients_destroy(guc);
	WARN_ON(!guc_verify_doorbells(guc));

	if (guc->stage_desc_pool)
		guc_stage_desc_pool_destroy(guc);
}

static void guc_interrupts_capture(struct intel_gt *gt)
{
	struct intel_rps *rps = &gt->i915->gt_pm.rps;
	struct intel_uncore *uncore = gt->uncore;
	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, gt, id)
		ENGINE_WRITE(engine, RING_MODE_GEN7, 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 */
	intel_uncore_write(uncore, GUC_BCS_RCS_IER, ~irqs);
	intel_uncore_write(uncore, GUC_VCS2_VCS1_IER, ~irqs);
	intel_uncore_write(uncore, 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!
	 */
	rps->pm_intrmsk_mbz |= ARAT_EXPIRED_INTRMSK;
	rps->pm_intrmsk_mbz &= ~GEN8_PMINTR_DISABLE_REDIRECT_TO_GUC;
}

static void guc_interrupts_release(struct intel_gt *gt)
{
	struct intel_rps *rps = &gt->i915->gt_pm.rps;
	struct intel_uncore *uncore = gt->uncore;
	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, gt, id)
		ENGINE_WRITE(engine, RING_MODE_GEN7, irqs);

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

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

static void guc_set_default_submission(struct intel_engine_cs *engine)
{
	/*
	 * We inherit a bunch of functions from execlists that we'd like
	 * to keep using:
	 *
	 *    engine->submit_request = execlists_submit_request;
	 *    engine->cancel_requests = execlists_cancel_requests;
	 *    engine->schedule = execlists_schedule;
	 *
	 * But we need to override the actual submission backend in order
	 * to talk to the GuC.
	 */
	intel_execlists_set_default_submission(engine);

	engine->execlists.tasklet.func = guc_submission_tasklet;

	/* do not use execlists park/unpark */
	engine->park = engine->unpark = NULL;

	engine->reset.prepare = guc_reset_prepare;
	engine->reset.reset = guc_reset;
	engine->reset.finish = guc_reset_finish;

	engine->cancel_requests = guc_cancel_requests;

	engine->flags &= ~I915_ENGINE_SUPPORTS_STATS;
	engine->flags |= I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;

	/*
	 * For the breadcrumb irq to work we need the interrupts to stay
	 * enabled. However, on all platforms on which we'll have support for
	 * GuC submission we don't allow disabling the interrupts at runtime, so
	 * we're always safe with the current flow.
	 */
	GEM_BUG_ON(engine->irq_enable || engine->irq_disable);
}

int intel_guc_submission_enable(struct intel_guc *guc)
{
	struct intel_gt *gt = guc_to_gt(guc);
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int err;

	err = i915_inject_load_error(gt->i915, -ENXIO);
	if (err)
		return err;

	/*
	 * We're using GuC work items for submitting work through GuC. Since
	 * we're coalescing multiple requests from a single context into a
	 * single work item prior to assigning it to execlist_port, we can
	 * never have more work items than the total number of ports (for all
	 * engines). The GuC firmware is controlling the HEAD of work queue,
	 * and it is guaranteed that it will remove the work item from the
	 * queue before our request is completed.
	 */
	BUILD_BUG_ON(ARRAY_SIZE(engine->execlists.inflight) *
		     sizeof(struct guc_wq_item) *
		     I915_NUM_ENGINES > GUC_WQ_SIZE);

	GEM_BUG_ON(!guc->execbuf_client);

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

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

	for_each_engine(engine, gt, id) {
		engine->set_default_submission = guc_set_default_submission;
		engine->set_default_submission(engine);
	}

	return 0;
}

void intel_guc_submission_disable(struct intel_guc *guc)
{
	struct intel_gt *gt = guc_to_gt(guc);

	GEM_BUG_ON(gt->awake); /* GT should be parked first */

	guc_interrupts_release(gt);
	guc_clients_disable(guc);
}

static bool __guc_submission_support(struct intel_guc *guc)
{
	/* XXX: GuC submission is unavailable for now */
	return false;

	if (!intel_guc_is_supported(guc))
		return false;

	return i915_modparams.enable_guc & ENABLE_GUC_SUBMISSION;
}

void intel_guc_submission_init_early(struct intel_guc *guc)
{
	guc->submission_supported = __guc_submission_support(guc);
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_guc.c"
#endif
