[dragonfly.git] / sys / dev / drm / i915 / i915_gem_context.c

/*
 * Copyright © 2011-2012 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:
 *    Ben Widawsky <ben@bwidawsk.net>
 *
 */

/*
 * This file implements HW context support. On gen5+ a HW context consists of an
 * opaque GPU object which is referenced at times of context saves and restores.
 * With RC6 enabled, the context is also referenced as the GPU enters and exists
 * from RC6 (GPU has it's own internal power context, except on gen5). Though
 * something like a context does exist for the media ring, the code only
 * supports contexts for the render ring.
 *
 * In software, there is a distinction between contexts created by the user,
 * and the default HW context. The default HW context is used by GPU clients
 * that do not request setup of their own hardware context. The default
 * context's state is never restored to help prevent programming errors. This
 * would happen if a client ran and piggy-backed off another clients GPU state.
 * The default context only exists to give the GPU some offset to load as the
 * current to invoke a save of the context we actually care about. In fact, the
 * code could likely be constructed, albeit in a more complicated fashion, to
 * never use the default context, though that limits the driver's ability to
 * swap out, and/or destroy other contexts.
 *
 * All other contexts are created as a request by the GPU client. These contexts
 * store GPU state, and thus allow GPU clients to not re-emit state (and
 * potentially query certain state) at any time. The kernel driver makes
 * certain that the appropriate commands are inserted.
 *
 * The context life cycle is semi-complicated in that context BOs may live
 * longer than the context itself because of the way the hardware, and object
 * tracking works. Below is a very crude representation of the state machine
 * describing the context life.
 *                                         refcount     pincount     active
 * S0: initial state                          0            0           0
 * S1: context created                        1            0           0
 * S2: context is currently running           2            1           X
 * S3: GPU referenced, but not current        2            0           1
 * S4: context is current, but destroyed      1            1           0
 * S5: like S3, but destroyed                 1            0           1
 *
 * The most common (but not all) transitions:
 * S0->S1: client creates a context
 * S1->S2: client submits execbuf with context
 * S2->S3: other clients submits execbuf with context
 * S3->S1: context object was retired
 * S3->S2: clients submits another execbuf
 * S2->S4: context destroy called with current context
 * S3->S5->S0: destroy path
 * S4->S5->S0: destroy path on current context
 *
 * There are two confusing terms used above:
 *  The "current context" means the context which is currently running on the
 *  GPU. The GPU has loaded it's state already and has stored away the gtt
 *  offset of the BO. The GPU is not actively referencing the data at this
 *  offset, but it will on the next context switch. The only way to avoid this
 *  is to do a GPU reset.
 *
 *  An "active context' is one which was previously the "current context" and is
 *  on the active list waiting for the next context switch to occur. Until this
 *  happens, the object must remain at the same gtt offset. It is therefore
 *  possible to destroy a context, but it is still active.
 *
 */

#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include <linux/err.h>

/* This is a HW constraint. The value below is the largest known requirement
 * I've seen in a spec to date, and that was a workaround for a non-shipping
 * part. It should be safe to decrease this, but it's more future proof as is.
 */
#define CONTEXT_ALIGN (64<<10)

static struct i915_hw_context *
i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id);
static int do_switch(struct i915_hw_context *to);

static int get_context_size(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;
        u32 reg;

        switch (INTEL_INFO(dev)->gen) {
        case 6:
                reg = I915_READ(CXT_SIZE);
                ret = GEN6_CXT_TOTAL_SIZE(reg) * 64;
                break;
        case 7:
                reg = I915_READ(GEN7_CXT_SIZE);
                if (IS_HASWELL(dev))
                        ret = HSW_CXT_TOTAL_SIZE(reg) * 64;
                else
                        ret = GEN7_CXT_TOTAL_SIZE(reg) * 64;
                break;
        default:
                BUG();
        }

        return ret;
}

static void do_destroy(struct i915_hw_context *ctx)
{
        if (ctx->file_priv)
                idr_remove(&ctx->file_priv->context_idr, ctx->id);

        drm_gem_object_unreference(&ctx->obj->base);
        kfree(ctx);
}

static struct i915_hw_context *
create_hw_context(struct drm_device *dev,
                  struct drm_i915_file_private *file_priv)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct i915_hw_context *ctx;
        int ret;

        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
        if (ctx == NULL)
                return ERR_PTR(-ENOMEM);

        ctx->obj = i915_gem_alloc_object(dev, dev_priv->hw_context_size);
        if (ctx->obj == NULL) {
                kfree(ctx);
                DRM_DEBUG_DRIVER("Context object allocated failed\n");
                return ERR_PTR(-ENOMEM);
        }

        if (INTEL_INFO(dev)->gen >= 7) {
                ret = i915_gem_object_set_cache_level(ctx->obj,
                                                      I915_CACHE_LLC_MLC);
                if (ret)
                        goto err_out;
        }

        /* The ring associated with the context object is handled by the normal
         * object tracking code. We give an initial ring value simple to pass an
         * assertion in the context switch code.
         */
        ctx->ring = &dev_priv->ring[RCS];

        /* Default context will never have a file_priv */
        if (file_priv == NULL)
                return ctx;

        ctx->file_priv = file_priv;

        ret = idr_alloc(&file_priv->context_idr, ctx, DEFAULT_CONTEXT_ID + 1, 0,
                        GFP_KERNEL);
        if (ret < 0)
                goto err_out;
        ctx->id = ret;

        return ctx;

err_out:
        do_destroy(ctx);
        return ERR_PTR(ret);
}

static inline bool is_default_context(struct i915_hw_context *ctx)
{
        return (ctx == ctx->ring->default_context);
}

/**
 * The default context needs to exist per ring that uses contexts. It stores the
 * context state of the GPU for applications that don't utilize HW contexts, as
 * well as an idle case.
 */
static int create_default_context(struct drm_i915_private *dev_priv)
{
        struct i915_hw_context *ctx;
        int ret;

        DRM_LOCK_ASSERT(dev_priv->dev);

        ctx = create_hw_context(dev_priv->dev, NULL);
        if (IS_ERR(ctx))
                return PTR_ERR(ctx);

        /* We may need to do things with the shrinker which require us to
         * immediately switch back to the default context. This can cause a
         * problem as pinning the default context also requires GTT space which
         * may not be available. To avoid this we always pin the
         * default context.
         */
        dev_priv->ring[RCS].default_context = ctx;
        ret = i915_gem_object_pin(ctx->obj, CONTEXT_ALIGN, false, false);
        if (ret)
                goto err_destroy;

        ret = do_switch(ctx);
        if (ret)
                goto err_unpin;

        DRM_DEBUG_DRIVER("Default HW context loaded\n");
        return 0;

err_unpin:
        i915_gem_object_unpin(ctx->obj);
err_destroy:
        do_destroy(ctx);
        return ret;
}

void i915_gem_context_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;

        if (!HAS_HW_CONTEXTS(dev)) {
                dev_priv->hw_contexts_disabled = true;
                return;
        }

        /* If called from reset, or thaw... we've been here already */
        if (dev_priv->hw_contexts_disabled ||
            dev_priv->ring[RCS].default_context)
                return;

        dev_priv->hw_context_size = round_up(get_context_size(dev), 4096);

        if (dev_priv->hw_context_size > (1<<20)) {
                dev_priv->hw_contexts_disabled = true;
                return;
        }

        if (create_default_context(dev_priv)) {
                dev_priv->hw_contexts_disabled = true;
                return;
        }

        DRM_DEBUG_DRIVER("HW context support initialized\n");
}

void i915_gem_context_fini(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;

        if (dev_priv->hw_contexts_disabled)
                return;

        /* The only known way to stop the gpu from accessing the hw context is
         * to reset it. Do this as the very last operation to avoid confusing
         * other code, leading to spurious errors. */
        intel_gpu_reset(dev);

        i915_gem_object_unpin(dev_priv->ring[RCS].default_context->obj);

        do_destroy(dev_priv->ring[RCS].default_context);
}

static int context_idr_cleanup(int id, void *p, void *data)
{
        struct i915_hw_context *ctx = p;

        BUG_ON(id == DEFAULT_CONTEXT_ID);

        do_destroy(ctx);

        return 0;
}

void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;

        mutex_lock(&dev->struct_mutex);
        idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
        idr_destroy(&file_priv->context_idr);
        mutex_unlock(&dev->struct_mutex);
}

static struct i915_hw_context *
i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id)
{
        return (struct i915_hw_context *)idr_find(&file_priv->context_idr, id);
}

static inline int
mi_set_context(struct intel_ring_buffer *ring,
               struct i915_hw_context *new_context,
               u32 hw_flags)
{
        int ret;

        /* w/a: If Flush TLB Invalidation Mode is enabled, driver must do a TLB
         * invalidation prior to MI_SET_CONTEXT. On GEN6 we don't set the value
         * explicitly, so we rely on the value at ring init, stored in
         * itlb_before_ctx_switch.
         */
        if (IS_GEN6(ring->dev) && ring->itlb_before_ctx_switch) {
                ret = ring->flush(ring, I915_GEM_GPU_DOMAINS, 0);
                if (ret)
                        return ret;
        }

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

        if (IS_GEN7(ring->dev))
                intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_DISABLE);
        else
                intel_ring_emit(ring, MI_NOOP);

        intel_ring_emit(ring, MI_NOOP);
        intel_ring_emit(ring, MI_SET_CONTEXT);
        intel_ring_emit(ring, new_context->obj->gtt_offset |
                        MI_MM_SPACE_GTT |
                        MI_SAVE_EXT_STATE_EN |
                        MI_RESTORE_EXT_STATE_EN |
                        hw_flags);
        /* w/a: MI_SET_CONTEXT must always be followed by MI_NOOP */
        intel_ring_emit(ring, MI_NOOP);

        if (IS_GEN7(ring->dev))
                intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_ENABLE);
        else
                intel_ring_emit(ring, MI_NOOP);

        intel_ring_advance(ring);

        return ret;
}

static int do_switch(struct i915_hw_context *to)
{
        struct intel_ring_buffer *ring = to->ring;
        struct drm_i915_gem_object *from_obj = ring->last_context_obj;
        u32 hw_flags = 0;
        int ret;

        BUG_ON(from_obj != NULL && from_obj->pin_count == 0);

        if (from_obj == to->obj)
                return 0;

        ret = i915_gem_object_pin(to->obj, CONTEXT_ALIGN, false, false);
        if (ret)
                return ret;

        /* Clear this page out of any CPU caches for coherent swap-in/out. Note
         * that thanks to write = false in this call and us not setting any gpu
         * write domains when putting a context object onto the active list
         * (when switching away from it), this won't block.
         * XXX: We need a real interface to do this instead of trickery. */
        ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
        if (ret) {
                i915_gem_object_unpin(to->obj);
                return ret;
        }

        if (!to->obj->has_global_gtt_mapping)
                i915_gem_gtt_bind_object(to->obj, to->obj->cache_level);

        if (!to->is_initialized || is_default_context(to))
                hw_flags |= MI_RESTORE_INHIBIT;
        else if (WARN_ON_ONCE(from_obj == to->obj)) /* not yet expected */
                hw_flags |= MI_FORCE_RESTORE;

        ret = mi_set_context(ring, to, hw_flags);
        if (ret) {
                i915_gem_object_unpin(to->obj);
                return ret;
        }

        /* The backing object for the context is done after switching to the
         * *next* context. Therefore we cannot retire the previous context until
         * the next context has already started running. In fact, the below code
         * is a bit suboptimal because the retiring can occur simply after the
         * MI_SET_CONTEXT instead of when the next seqno has completed.
         */
        if (from_obj != NULL) {
                from_obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
                i915_gem_object_move_to_active(from_obj, ring);
                /* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
                 * whole damn pipeline, we don't need to explicitly mark the
                 * object dirty. The only exception is that the context must be
                 * correct in case the object gets swapped out. Ideally we'd be
                 * able to defer doing this until we know the object would be
                 * swapped, but there is no way to do that yet.
                 */
                from_obj->dirty = 1;
                BUG_ON(from_obj->ring != ring);
                i915_gem_object_unpin(from_obj);

                drm_gem_object_unreference(&from_obj->base);
        }

        drm_gem_object_reference(&to->obj->base);
        ring->last_context_obj = to->obj;
        to->is_initialized = true;

        return 0;
}

/**
 * i915_switch_context() - perform a GPU context switch.
 * @ring: ring for which we'll execute the context switch
 * @file_priv: file_priv associated with the context, may be NULL
 * @id: context id number
 * @seqno: sequence number by which the new context will be switched to
 * @flags:
 *
 * The context life cycle is simple. The context refcount is incremented and
 * decremented by 1 and create and destroy. If the context is in use by the GPU,
 * it will have a refoucnt > 1. This allows us to destroy the context abstract
 * object while letting the normal object tracking destroy the backing BO.
 */
int i915_switch_context(struct intel_ring_buffer *ring,
                        struct drm_file *file,
                        int to_id)
{
        struct drm_i915_private *dev_priv = ring->dev->dev_private;
        struct i915_hw_context *to;

        if (dev_priv->hw_contexts_disabled)
                return 0;

        if (ring != &dev_priv->ring[RCS])
                return 0;

        if (to_id == DEFAULT_CONTEXT_ID) {
                to = ring->default_context;
        } else {
                if (file == NULL)
                        return -EINVAL;

                to = i915_gem_context_get(file->driver_priv, to_id);
                if (to == NULL)
                        return -ENOENT;
        }

        return do_switch(to);
}

int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
                                  struct drm_file *file)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_i915_gem_context_create *args = data;
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct i915_hw_context *ctx;
        int ret;

        if (!(dev->driver->driver_features & DRIVER_GEM))
                return -ENODEV;

        if (dev_priv->hw_contexts_disabled)
                return -ENODEV;

        ret = i915_mutex_lock_interruptible(dev);
        if (ret)
                return ret;

        ctx = create_hw_context(dev, file_priv);
        mutex_unlock(&dev->struct_mutex);
        if (IS_ERR(ctx))
                return PTR_ERR(ctx);

        args->ctx_id = ctx->id;
        DRM_DEBUG_DRIVER("HW context %d created\n", args->ctx_id);

        return 0;
}

int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
                                   struct drm_file *file)
{
        struct drm_i915_gem_context_destroy *args = data;
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct i915_hw_context *ctx;
        int ret;

        if (!(dev->driver->driver_features & DRIVER_GEM))
                return -ENODEV;

        ret = i915_mutex_lock_interruptible(dev);
        if (ret)
                return ret;

        ctx = i915_gem_context_get(file_priv, args->ctx_id);
        if (!ctx) {
                mutex_unlock(&dev->struct_mutex);
                return -ENOENT;
        }

        do_destroy(ctx);

        mutex_unlock(&dev->struct_mutex);

        DRM_DEBUG_DRIVER("HW context %d destroyed\n", args->ctx_id);
        return 0;
}