/*
 * 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.
 *
 * Authors:
 *      Daniel Vetter <daniel.vetter@ffwll.ch>
 */

/**
 * DOC: frontbuffer tracking
 *
 * Many features require us to track changes to the currently active
 * frontbuffer, especially rendering targeted at the frontbuffer.
 *
 * To be able to do so we track frontbuffers using a bitmask for all possible
 * frontbuffer slots through intel_frontbuffer_track(). The functions in this
 * file are then called when the contents of the frontbuffer are invalidated,
 * when frontbuffer rendering has stopped again to flush out all the changes
 * and when the frontbuffer is exchanged with a flip. Subsystems interested in
 * frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
 * into the relevant places and filter for the frontbuffer slots that they are
 * interested int.
 *
 * On a high level there are two types of powersaving features. The first one
 * work like a special cache (FBC and PSR) and are interested when they should
 * stop caching and when to restart caching. This is done by placing callbacks
 * into the invalidate and the flush functions: At invalidate the caching must
 * be stopped and at flush time it can be restarted. And maybe they need to know
 * when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
 * and flush on its own) which can be achieved with placing callbacks into the
 * flip functions.
 *
 * The other type of display power saving feature only cares about busyness
 * (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
 * busyness. There is no direct way to detect idleness. Instead an idle timer
 * work delayed work should be started from the flush and flip functions and
 * cancelled as soon as busyness is detected.
 */

#include "display/intel_dp.h"

#include "i915_drv.h"
#include "intel_display_types.h"
#include "intel_fbc.h"
#include "intel_frontbuffer.h"
#include "intel_psr.h"

/**
 * frontbuffer_flush - flush frontbuffer
 * @i915: i915 device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 * @origin: which operation caused the flush
 *
 * This function gets called every time rendering on the given planes has
 * completed and frontbuffer caching can be started again. Flushes will get
 * delayed if they're blocked by some outstanding asynchronous rendering.
 *
 * Can be called without any locks held.
 */
static void frontbuffer_flush(struct drm_i915_private *i915,
                              unsigned int frontbuffer_bits,
                              enum fb_op_origin origin)
{
        /* Delay flushing when rings are still busy.*/
        spin_lock(&i915->fb_tracking.lock);
        frontbuffer_bits &= ~i915->fb_tracking.busy_bits;
        spin_unlock(&i915->fb_tracking.lock);

        if (!frontbuffer_bits)
                return;

        might_sleep();
        intel_edp_drrs_flush(i915, frontbuffer_bits);
        intel_psr_flush(i915, frontbuffer_bits, origin);
        intel_fbc_flush(i915, frontbuffer_bits, origin);
}

/**
 * intel_frontbuffer_flip_prepare - prepare asynchronous frontbuffer flip
 * @i915: i915 device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after scheduling a flip on @obj. The actual
 * frontbuffer flushing will be delayed until completion is signalled with
 * intel_frontbuffer_flip_complete. If an invalidate happens in between this
 * flush will be cancelled.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flip_prepare(struct drm_i915_private *i915,
                                    unsigned frontbuffer_bits)
{
        spin_lock(&i915->fb_tracking.lock);
        i915->fb_tracking.flip_bits |= frontbuffer_bits;
        /* Remove stale busy bits due to the old buffer. */
        i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
        spin_unlock(&i915->fb_tracking.lock);
}

/**
 * intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flip
 * @i915: i915 device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after the flip has been latched and will complete
 * on the next vblank. It will execute the flush if it hasn't been cancelled yet.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flip_complete(struct drm_i915_private *i915,
                                     unsigned frontbuffer_bits)
{
        spin_lock(&i915->fb_tracking.lock);
        /* Mask any cancelled flips. */
        frontbuffer_bits &= i915->fb_tracking.flip_bits;
        i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
        spin_unlock(&i915->fb_tracking.lock);

        if (frontbuffer_bits)
                frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
}

/**
 * intel_frontbuffer_flip - synchronous frontbuffer flip
 * @i915: i915 device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after scheduling a flip on @obj. This is for
 * synchronous plane updates which will happen on the next vblank and which will
 * not get delayed by pending gpu rendering.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flip(struct drm_i915_private *i915,
                            unsigned frontbuffer_bits)
{
        spin_lock(&i915->fb_tracking.lock);
        /* Remove stale busy bits due to the old buffer. */
        i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
        spin_unlock(&i915->fb_tracking.lock);

        frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
}

void __intel_fb_invalidate(struct intel_frontbuffer *front,
                           enum fb_op_origin origin,
                           unsigned int frontbuffer_bits)
{
        struct drm_i915_private *i915 = to_i915(front->obj->base.dev);

        if (origin == ORIGIN_CS) {
                spin_lock(&i915->fb_tracking.lock);
                i915->fb_tracking.busy_bits |= frontbuffer_bits;
                i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
                spin_unlock(&i915->fb_tracking.lock);
        }

        might_sleep();
        intel_psr_invalidate(i915, frontbuffer_bits, origin);
        intel_edp_drrs_invalidate(i915, frontbuffer_bits);
        intel_fbc_invalidate(i915, frontbuffer_bits, origin);
}

void __intel_fb_flush(struct intel_frontbuffer *front,
                      enum fb_op_origin origin,
                      unsigned int frontbuffer_bits)
{
        struct drm_i915_private *i915 = to_i915(front->obj->base.dev);

        if (origin == ORIGIN_CS) {
                spin_lock(&i915->fb_tracking.lock);
                /* Filter out new bits since rendering started. */
                frontbuffer_bits &= i915->fb_tracking.busy_bits;
                i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
                spin_unlock(&i915->fb_tracking.lock);
        }

        if (frontbuffer_bits)
                frontbuffer_flush(i915, frontbuffer_bits, origin);
}

static int frontbuffer_active(struct i915_active *ref)
{
        struct intel_frontbuffer *front =
                container_of(ref, typeof(*front), write);

        kref_get(&front->ref);
        return 0;
}

__i915_active_call
static void frontbuffer_retire(struct i915_active *ref)
{
        struct intel_frontbuffer *front =
                container_of(ref, typeof(*front), write);

        intel_frontbuffer_flush(front, ORIGIN_CS);
        intel_frontbuffer_put(front);
}

static void frontbuffer_release(struct kref *ref)
        __releases(&to_i915(front->obj->base.dev)->fb_tracking.lock)
{
        struct intel_frontbuffer *front =
                container_of(ref, typeof(*front), ref);
        struct drm_i915_gem_object *obj = front->obj;
        struct i915_vma *vma;

        spin_lock(&obj->vma.lock);
        for_each_ggtt_vma(vma, obj) {
                i915_vma_clear_scanout(vma);
                vma->display_alignment = I915_GTT_MIN_ALIGNMENT;
        }
        spin_unlock(&obj->vma.lock);

        RCU_INIT_POINTER(obj->frontbuffer, NULL);
        spin_unlock(&to_i915(obj->base.dev)->fb_tracking.lock);

        i915_active_fini(&front->write);

        i915_gem_object_put(obj);
        kfree_rcu(front, rcu);
}

struct intel_frontbuffer *
intel_frontbuffer_get(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        struct intel_frontbuffer *front;

        front = __intel_frontbuffer_get(obj);
        if (front)
                return front;

        front = kmalloc(sizeof(*front), GFP_KERNEL);
        if (!front)
                return NULL;

        front->obj = obj;
        kref_init(&front->ref);
        atomic_set(&front->bits, 0);
        i915_active_init(&front->write,
                         frontbuffer_active,
                         i915_active_may_sleep(frontbuffer_retire));

        spin_lock(&i915->fb_tracking.lock);
        if (rcu_access_pointer(obj->frontbuffer)) {
                kfree(front);
                front = rcu_dereference_protected(obj->frontbuffer, true);
                kref_get(&front->ref);
        } else {
                i915_gem_object_get(obj);
                rcu_assign_pointer(obj->frontbuffer, front);
        }
        spin_unlock(&i915->fb_tracking.lock);

        return front;
}

void intel_frontbuffer_put(struct intel_frontbuffer *front)
{
        kref_put_lock(&front->ref,
                      frontbuffer_release,
                      &to_i915(front->obj->base.dev)->fb_tracking.lock);
}

/**
 * intel_frontbuffer_track - update frontbuffer tracking
 * @old: current buffer for the frontbuffer slots
 * @new: new buffer for the frontbuffer slots
 * @frontbuffer_bits: bitmask of frontbuffer slots
 *
 * This updates the frontbuffer tracking bits @frontbuffer_bits by clearing them
 * from @old and setting them in @new. Both @old and @new can be NULL.
 */
void intel_frontbuffer_track(struct intel_frontbuffer *old,
                             struct intel_frontbuffer *new,
                             unsigned int frontbuffer_bits)
{
        /*
         * Control of individual bits within the mask are guarded by
         * the owning plane->mutex, i.e. we can never see concurrent
         * manipulation of individual bits. But since the bitfield as a whole
         * is updated using RMW, we need to use atomics in order to update
         * the bits.
         */
        BUILD_BUG_ON(INTEL_FRONTBUFFER_BITS_PER_PIPE * I915_MAX_PIPES >
                     BITS_PER_TYPE(atomic_t));

        if (old) {
                drm_WARN_ON(old->obj->base.dev,
                            !(atomic_read(&old->bits) & frontbuffer_bits));
                atomic_andnot(frontbuffer_bits, &old->bits);
        }

        if (new) {
                drm_WARN_ON(new->obj->base.dev,
                            atomic_read(&new->bits) & frontbuffer_bits);
                atomic_or(frontbuffer_bits, &new->bits);
        }
}