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Diffstat (limited to 'drivers/gpu/drm/i915/gem/i915_gem_domain.c')
-rw-r--r--drivers/gpu/drm/i915/gem/i915_gem_domain.c740
1 files changed, 740 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
new file mode 100644
index 000000000..d44a152ce
--- /dev/null
+++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
@@ -0,0 +1,740 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2014-2016 Intel Corporation
+ */
+
+#include "display/intel_frontbuffer.h"
+#include "gt/intel_gt.h"
+
+#include "i915_drv.h"
+#include "i915_gem_clflush.h"
+#include "i915_gem_domain.h"
+#include "i915_gem_gtt.h"
+#include "i915_gem_ioctls.h"
+#include "i915_gem_lmem.h"
+#include "i915_gem_mman.h"
+#include "i915_gem_object.h"
+#include "i915_vma.h"
+
+static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
+{
+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
+ if (IS_DGFX(i915))
+ return false;
+
+ return !(obj->cache_level == I915_CACHE_NONE ||
+ obj->cache_level == I915_CACHE_WT);
+}
+
+bool i915_gem_cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
+{
+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
+ if (obj->cache_dirty)
+ return false;
+
+ if (IS_DGFX(i915))
+ return false;
+
+ if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE))
+ return true;
+
+ /* Currently in use by HW (display engine)? Keep flushed. */
+ return i915_gem_object_is_framebuffer(obj);
+}
+
+static void
+flush_write_domain(struct drm_i915_gem_object *obj, unsigned int flush_domains)
+{
+ struct i915_vma *vma;
+
+ assert_object_held(obj);
+
+ if (!(obj->write_domain & flush_domains))
+ return;
+
+ switch (obj->write_domain) {
+ case I915_GEM_DOMAIN_GTT:
+ spin_lock(&obj->vma.lock);
+ for_each_ggtt_vma(vma, obj) {
+ if (i915_vma_unset_ggtt_write(vma))
+ intel_gt_flush_ggtt_writes(vma->vm->gt);
+ }
+ spin_unlock(&obj->vma.lock);
+
+ i915_gem_object_flush_frontbuffer(obj, ORIGIN_CPU);
+ break;
+
+ case I915_GEM_DOMAIN_WC:
+ wmb();
+ break;
+
+ case I915_GEM_DOMAIN_CPU:
+ i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
+ break;
+
+ case I915_GEM_DOMAIN_RENDER:
+ if (gpu_write_needs_clflush(obj))
+ obj->cache_dirty = true;
+ break;
+ }
+
+ obj->write_domain = 0;
+}
+
+static void __i915_gem_object_flush_for_display(struct drm_i915_gem_object *obj)
+{
+ /*
+ * We manually flush the CPU domain so that we can override and
+ * force the flush for the display, and perform it asyncrhonously.
+ */
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
+ if (obj->cache_dirty)
+ i915_gem_clflush_object(obj, I915_CLFLUSH_FORCE);
+ obj->write_domain = 0;
+}
+
+void i915_gem_object_flush_if_display(struct drm_i915_gem_object *obj)
+{
+ if (!i915_gem_object_is_framebuffer(obj))
+ return;
+
+ i915_gem_object_lock(obj, NULL);
+ __i915_gem_object_flush_for_display(obj);
+ i915_gem_object_unlock(obj);
+}
+
+void i915_gem_object_flush_if_display_locked(struct drm_i915_gem_object *obj)
+{
+ if (i915_gem_object_is_framebuffer(obj))
+ __i915_gem_object_flush_for_display(obj);
+}
+
+/**
+ * Moves a single object to the WC read, and possibly write domain.
+ * @obj: object to act on
+ * @write: ask for write access or read only
+ *
+ * This function returns when the move is complete, including waiting on
+ * flushes to occur.
+ */
+int
+i915_gem_object_set_to_wc_domain(struct drm_i915_gem_object *obj, bool write)
+{
+ int ret;
+
+ assert_object_held(obj);
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ (write ? I915_WAIT_ALL : 0),
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ if (obj->write_domain == I915_GEM_DOMAIN_WC)
+ return 0;
+
+ /* Flush and acquire obj->pages so that we are coherent through
+ * direct access in memory with previous cached writes through
+ * shmemfs and that our cache domain tracking remains valid.
+ * For example, if the obj->filp was moved to swap without us
+ * being notified and releasing the pages, we would mistakenly
+ * continue to assume that the obj remained out of the CPU cached
+ * domain.
+ */
+ ret = i915_gem_object_pin_pages(obj);
+ if (ret)
+ return ret;
+
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_WC);
+
+ /* Serialise direct access to this object with the barriers for
+ * coherent writes from the GPU, by effectively invalidating the
+ * WC domain upon first access.
+ */
+ if ((obj->read_domains & I915_GEM_DOMAIN_WC) == 0)
+ mb();
+
+ /* It should now be out of any other write domains, and we can update
+ * the domain values for our changes.
+ */
+ GEM_BUG_ON((obj->write_domain & ~I915_GEM_DOMAIN_WC) != 0);
+ obj->read_domains |= I915_GEM_DOMAIN_WC;
+ if (write) {
+ obj->read_domains = I915_GEM_DOMAIN_WC;
+ obj->write_domain = I915_GEM_DOMAIN_WC;
+ obj->mm.dirty = true;
+ }
+
+ i915_gem_object_unpin_pages(obj);
+ return 0;
+}
+
+/**
+ * Moves a single object to the GTT read, and possibly write domain.
+ * @obj: object to act on
+ * @write: ask for write access or read only
+ *
+ * This function returns when the move is complete, including waiting on
+ * flushes to occur.
+ */
+int
+i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj, bool write)
+{
+ int ret;
+
+ assert_object_held(obj);
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ (write ? I915_WAIT_ALL : 0),
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ if (obj->write_domain == I915_GEM_DOMAIN_GTT)
+ return 0;
+
+ /* Flush and acquire obj->pages so that we are coherent through
+ * direct access in memory with previous cached writes through
+ * shmemfs and that our cache domain tracking remains valid.
+ * For example, if the obj->filp was moved to swap without us
+ * being notified and releasing the pages, we would mistakenly
+ * continue to assume that the obj remained out of the CPU cached
+ * domain.
+ */
+ ret = i915_gem_object_pin_pages(obj);
+ if (ret)
+ return ret;
+
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_GTT);
+
+ /* Serialise direct access to this object with the barriers for
+ * coherent writes from the GPU, by effectively invalidating the
+ * GTT domain upon first access.
+ */
+ if ((obj->read_domains & I915_GEM_DOMAIN_GTT) == 0)
+ mb();
+
+ /* It should now be out of any other write domains, and we can update
+ * the domain values for our changes.
+ */
+ GEM_BUG_ON((obj->write_domain & ~I915_GEM_DOMAIN_GTT) != 0);
+ obj->read_domains |= I915_GEM_DOMAIN_GTT;
+ if (write) {
+ struct i915_vma *vma;
+
+ obj->read_domains = I915_GEM_DOMAIN_GTT;
+ obj->write_domain = I915_GEM_DOMAIN_GTT;
+ obj->mm.dirty = true;
+
+ spin_lock(&obj->vma.lock);
+ for_each_ggtt_vma(vma, obj)
+ if (i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND))
+ i915_vma_set_ggtt_write(vma);
+ spin_unlock(&obj->vma.lock);
+ }
+
+ i915_gem_object_unpin_pages(obj);
+ return 0;
+}
+
+/**
+ * Changes the cache-level of an object across all VMA.
+ * @obj: object to act on
+ * @cache_level: new cache level to set for the object
+ *
+ * After this function returns, the object will be in the new cache-level
+ * across all GTT and the contents of the backing storage will be coherent,
+ * with respect to the new cache-level. In order to keep the backing storage
+ * coherent for all users, we only allow a single cache level to be set
+ * globally on the object and prevent it from being changed whilst the
+ * hardware is reading from the object. That is if the object is currently
+ * on the scanout it will be set to uncached (or equivalent display
+ * cache coherency) and all non-MOCS GPU access will also be uncached so
+ * that all direct access to the scanout remains coherent.
+ */
+int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
+ enum i915_cache_level cache_level)
+{
+ int ret;
+
+ if (obj->cache_level == cache_level)
+ return 0;
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_ALL,
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ /* Always invalidate stale cachelines */
+ if (obj->cache_level != cache_level) {
+ i915_gem_object_set_cache_coherency(obj, cache_level);
+ obj->cache_dirty = true;
+ }
+
+ /* The cache-level will be applied when each vma is rebound. */
+ return i915_gem_object_unbind(obj,
+ I915_GEM_OBJECT_UNBIND_ACTIVE |
+ I915_GEM_OBJECT_UNBIND_BARRIER);
+}
+
+int i915_gem_get_caching_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file)
+{
+ struct drm_i915_gem_caching *args = data;
+ struct drm_i915_gem_object *obj;
+ int err = 0;
+
+ if (IS_DGFX(to_i915(dev)))
+ return -ENODEV;
+
+ rcu_read_lock();
+ obj = i915_gem_object_lookup_rcu(file, args->handle);
+ if (!obj) {
+ err = -ENOENT;
+ goto out;
+ }
+
+ switch (obj->cache_level) {
+ case I915_CACHE_LLC:
+ case I915_CACHE_L3_LLC:
+ args->caching = I915_CACHING_CACHED;
+ break;
+
+ case I915_CACHE_WT:
+ args->caching = I915_CACHING_DISPLAY;
+ break;
+
+ default:
+ args->caching = I915_CACHING_NONE;
+ break;
+ }
+out:
+ rcu_read_unlock();
+ return err;
+}
+
+int i915_gem_set_caching_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file)
+{
+ struct drm_i915_private *i915 = to_i915(dev);
+ struct drm_i915_gem_caching *args = data;
+ struct drm_i915_gem_object *obj;
+ enum i915_cache_level level;
+ int ret = 0;
+
+ if (IS_DGFX(i915))
+ return -ENODEV;
+
+ switch (args->caching) {
+ case I915_CACHING_NONE:
+ level = I915_CACHE_NONE;
+ break;
+ case I915_CACHING_CACHED:
+ /*
+ * Due to a HW issue on BXT A stepping, GPU stores via a
+ * snooped mapping may leave stale data in a corresponding CPU
+ * cacheline, whereas normally such cachelines would get
+ * invalidated.
+ */
+ if (!HAS_LLC(i915) && !HAS_SNOOP(i915))
+ return -ENODEV;
+
+ level = I915_CACHE_LLC;
+ break;
+ case I915_CACHING_DISPLAY:
+ level = HAS_WT(i915) ? I915_CACHE_WT : I915_CACHE_NONE;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ obj = i915_gem_object_lookup(file, args->handle);
+ if (!obj)
+ return -ENOENT;
+
+ /*
+ * The caching mode of proxy object is handled by its generator, and
+ * not allowed to be changed by userspace.
+ */
+ if (i915_gem_object_is_proxy(obj)) {
+ /*
+ * Silently allow cached for userptr; the vulkan driver
+ * sets all objects to cached
+ */
+ if (!i915_gem_object_is_userptr(obj) ||
+ args->caching != I915_CACHING_CACHED)
+ ret = -ENXIO;
+
+ goto out;
+ }
+
+ ret = i915_gem_object_lock_interruptible(obj, NULL);
+ if (ret)
+ goto out;
+
+ ret = i915_gem_object_set_cache_level(obj, level);
+ i915_gem_object_unlock(obj);
+
+out:
+ i915_gem_object_put(obj);
+ return ret;
+}
+
+/*
+ * Prepare buffer for display plane (scanout, cursors, etc). Can be called from
+ * an uninterruptible phase (modesetting) and allows any flushes to be pipelined
+ * (for pageflips). We only flush the caches while preparing the buffer for
+ * display, the callers are responsible for frontbuffer flush.
+ */
+struct i915_vma *
+i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
+ struct i915_gem_ww_ctx *ww,
+ u32 alignment,
+ const struct i915_gtt_view *view,
+ unsigned int flags)
+{
+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
+ struct i915_vma *vma;
+ int ret;
+
+ /* Frame buffer must be in LMEM */
+ if (HAS_LMEM(i915) && !i915_gem_object_is_lmem(obj))
+ return ERR_PTR(-EINVAL);
+
+ /*
+ * The display engine is not coherent with the LLC cache on gen6. As
+ * a result, we make sure that the pinning that is about to occur is
+ * done with uncached PTEs. This is lowest common denominator for all
+ * chipsets.
+ *
+ * However for gen6+, we could do better by using the GFDT bit instead
+ * of uncaching, which would allow us to flush all the LLC-cached data
+ * with that bit in the PTE to main memory with just one PIPE_CONTROL.
+ */
+ ret = i915_gem_object_set_cache_level(obj,
+ HAS_WT(i915) ?
+ I915_CACHE_WT : I915_CACHE_NONE);
+ if (ret)
+ return ERR_PTR(ret);
+
+ /*
+ * As the user may map the buffer once pinned in the display plane
+ * (e.g. libkms for the bootup splash), we have to ensure that we
+ * always use map_and_fenceable for all scanout buffers. However,
+ * it may simply be too big to fit into mappable, in which case
+ * put it anyway and hope that userspace can cope (but always first
+ * try to preserve the existing ABI).
+ */
+ vma = ERR_PTR(-ENOSPC);
+ if ((flags & PIN_MAPPABLE) == 0 &&
+ (!view || view->type == I915_GTT_VIEW_NORMAL))
+ vma = i915_gem_object_ggtt_pin_ww(obj, ww, view, 0, alignment,
+ flags | PIN_MAPPABLE |
+ PIN_NONBLOCK);
+ if (IS_ERR(vma) && vma != ERR_PTR(-EDEADLK))
+ vma = i915_gem_object_ggtt_pin_ww(obj, ww, view, 0,
+ alignment, flags);
+ if (IS_ERR(vma))
+ return vma;
+
+ vma->display_alignment = max_t(u64, vma->display_alignment, alignment);
+ i915_vma_mark_scanout(vma);
+
+ i915_gem_object_flush_if_display_locked(obj);
+
+ return vma;
+}
+
+/**
+ * Moves a single object to the CPU read, and possibly write domain.
+ * @obj: object to act on
+ * @write: requesting write or read-only access
+ *
+ * This function returns when the move is complete, including waiting on
+ * flushes to occur.
+ */
+int
+i915_gem_object_set_to_cpu_domain(struct drm_i915_gem_object *obj, bool write)
+{
+ int ret;
+
+ assert_object_held(obj);
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ (write ? I915_WAIT_ALL : 0),
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
+
+ /* Flush the CPU cache if it's still invalid. */
+ if ((obj->read_domains & I915_GEM_DOMAIN_CPU) == 0) {
+ i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
+ obj->read_domains |= I915_GEM_DOMAIN_CPU;
+ }
+
+ /* It should now be out of any other write domains, and we can update
+ * the domain values for our changes.
+ */
+ GEM_BUG_ON(obj->write_domain & ~I915_GEM_DOMAIN_CPU);
+
+ /* If we're writing through the CPU, then the GPU read domains will
+ * need to be invalidated at next use.
+ */
+ if (write)
+ __start_cpu_write(obj);
+
+ return 0;
+}
+
+/**
+ * Called when user space prepares to use an object with the CPU, either
+ * through the mmap ioctl's mapping or a GTT mapping.
+ * @dev: drm device
+ * @data: ioctl data blob
+ * @file: drm file
+ */
+int
+i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file)
+{
+ struct drm_i915_gem_set_domain *args = data;
+ struct drm_i915_gem_object *obj;
+ u32 read_domains = args->read_domains;
+ u32 write_domain = args->write_domain;
+ int err;
+
+ if (IS_DGFX(to_i915(dev)))
+ return -ENODEV;
+
+ /* Only handle setting domains to types used by the CPU. */
+ if ((write_domain | read_domains) & I915_GEM_GPU_DOMAINS)
+ return -EINVAL;
+
+ /*
+ * Having something in the write domain implies it's in the read
+ * domain, and only that read domain. Enforce that in the request.
+ */
+ if (write_domain && read_domains != write_domain)
+ return -EINVAL;
+
+ if (!read_domains)
+ return 0;
+
+ obj = i915_gem_object_lookup(file, args->handle);
+ if (!obj)
+ return -ENOENT;
+
+ /*
+ * Try to flush the object off the GPU without holding the lock.
+ * We will repeat the flush holding the lock in the normal manner
+ * to catch cases where we are gazumped.
+ */
+ err = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_PRIORITY |
+ (write_domain ? I915_WAIT_ALL : 0),
+ MAX_SCHEDULE_TIMEOUT);
+ if (err)
+ goto out;
+
+ if (i915_gem_object_is_userptr(obj)) {
+ /*
+ * Try to grab userptr pages, iris uses set_domain to check
+ * userptr validity
+ */
+ err = i915_gem_object_userptr_validate(obj);
+ if (!err)
+ err = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_PRIORITY |
+ (write_domain ? I915_WAIT_ALL : 0),
+ MAX_SCHEDULE_TIMEOUT);
+ goto out;
+ }
+
+ /*
+ * Proxy objects do not control access to the backing storage, ergo
+ * they cannot be used as a means to manipulate the cache domain
+ * tracking for that backing storage. The proxy object is always
+ * considered to be outside of any cache domain.
+ */
+ if (i915_gem_object_is_proxy(obj)) {
+ err = -ENXIO;
+ goto out;
+ }
+
+ err = i915_gem_object_lock_interruptible(obj, NULL);
+ if (err)
+ goto out;
+
+ /*
+ * Flush and acquire obj->pages so that we are coherent through
+ * direct access in memory with previous cached writes through
+ * shmemfs and that our cache domain tracking remains valid.
+ * For example, if the obj->filp was moved to swap without us
+ * being notified and releasing the pages, we would mistakenly
+ * continue to assume that the obj remained out of the CPU cached
+ * domain.
+ */
+ err = i915_gem_object_pin_pages(obj);
+ if (err)
+ goto out_unlock;
+
+ /*
+ * Already in the desired write domain? Nothing for us to do!
+ *
+ * We apply a little bit of cunning here to catch a broader set of
+ * no-ops. If obj->write_domain is set, we must be in the same
+ * obj->read_domains, and only that domain. Therefore, if that
+ * obj->write_domain matches the request read_domains, we are
+ * already in the same read/write domain and can skip the operation,
+ * without having to further check the requested write_domain.
+ */
+ if (READ_ONCE(obj->write_domain) == read_domains)
+ goto out_unpin;
+
+ if (read_domains & I915_GEM_DOMAIN_WC)
+ err = i915_gem_object_set_to_wc_domain(obj, write_domain);
+ else if (read_domains & I915_GEM_DOMAIN_GTT)
+ err = i915_gem_object_set_to_gtt_domain(obj, write_domain);
+ else
+ err = i915_gem_object_set_to_cpu_domain(obj, write_domain);
+
+out_unpin:
+ i915_gem_object_unpin_pages(obj);
+
+out_unlock:
+ i915_gem_object_unlock(obj);
+
+ if (!err && write_domain)
+ i915_gem_object_invalidate_frontbuffer(obj, ORIGIN_CPU);
+
+out:
+ i915_gem_object_put(obj);
+ return err;
+}
+
+/*
+ * Pins the specified object's pages and synchronizes the object with
+ * GPU accesses. Sets needs_clflush to non-zero if the caller should
+ * flush the object from the CPU cache.
+ */
+int i915_gem_object_prepare_read(struct drm_i915_gem_object *obj,
+ unsigned int *needs_clflush)
+{
+ int ret;
+
+ *needs_clflush = 0;
+ if (!i915_gem_object_has_struct_page(obj))
+ return -ENODEV;
+
+ assert_object_held(obj);
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE,
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ ret = i915_gem_object_pin_pages(obj);
+ if (ret)
+ return ret;
+
+ if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ ||
+ !static_cpu_has(X86_FEATURE_CLFLUSH)) {
+ ret = i915_gem_object_set_to_cpu_domain(obj, false);
+ if (ret)
+ goto err_unpin;
+ else
+ goto out;
+ }
+
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
+
+ /* If we're not in the cpu read domain, set ourself into the gtt
+ * read domain and manually flush cachelines (if required). This
+ * optimizes for the case when the gpu will dirty the data
+ * anyway again before the next pread happens.
+ */
+ if (!obj->cache_dirty &&
+ !(obj->read_domains & I915_GEM_DOMAIN_CPU))
+ *needs_clflush = CLFLUSH_BEFORE;
+
+out:
+ /* return with the pages pinned */
+ return 0;
+
+err_unpin:
+ i915_gem_object_unpin_pages(obj);
+ return ret;
+}
+
+int i915_gem_object_prepare_write(struct drm_i915_gem_object *obj,
+ unsigned int *needs_clflush)
+{
+ int ret;
+
+ *needs_clflush = 0;
+ if (!i915_gem_object_has_struct_page(obj))
+ return -ENODEV;
+
+ assert_object_held(obj);
+
+ ret = i915_gem_object_wait(obj,
+ I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_ALL,
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret)
+ return ret;
+
+ ret = i915_gem_object_pin_pages(obj);
+ if (ret)
+ return ret;
+
+ if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE ||
+ !static_cpu_has(X86_FEATURE_CLFLUSH)) {
+ ret = i915_gem_object_set_to_cpu_domain(obj, true);
+ if (ret)
+ goto err_unpin;
+ else
+ goto out;
+ }
+
+ flush_write_domain(obj, ~I915_GEM_DOMAIN_CPU);
+
+ /* If we're not in the cpu write domain, set ourself into the
+ * gtt write domain and manually flush cachelines (as required).
+ * This optimizes for the case when the gpu will use the data
+ * right away and we therefore have to clflush anyway.
+ */
+ if (!obj->cache_dirty) {
+ *needs_clflush |= CLFLUSH_AFTER;
+
+ /*
+ * Same trick applies to invalidate partially written
+ * cachelines read before writing.
+ */
+ if (!(obj->read_domains & I915_GEM_DOMAIN_CPU))
+ *needs_clflush |= CLFLUSH_BEFORE;
+ }
+
+out:
+ i915_gem_object_invalidate_frontbuffer(obj, ORIGIN_CPU);
+ obj->mm.dirty = true;
+ /* return with the pages pinned */
+ return 0;
+
+err_unpin:
+ i915_gem_object_unpin_pages(obj);
+ return ret;
+}