[PATCH v3 33/37] drm/i915: cpu-map based dumb buffers

[Chris Wilson]

Quoting Matthew Auld (2019-08-09 23:26:39)
> From: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> 
> If there is no aperture we can't use map_gtt to map dumb buffers, so we
> need a cpu-map based path to do it. We prefer map_gtt on platforms that
> do have aperture.
> 
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_mman.c       | 18 +++++++++++++++++-
>  .../gpu/drm/i915/gem/i915_gem_object_types.h   |  1 +
>  drivers/gpu/drm/i915/i915_drv.c                |  2 +-
>  drivers/gpu/drm/i915/i915_drv.h                |  2 +-
>  4 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> index 304ea578fd30..4fe83e31c1b3 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> @@ -500,7 +500,8 @@ static void i915_gem_object_release_mmap_offset(struct drm_i915_gem_object *obj)
>         list_for_each_entry(mmo, &obj->mmap_offsets, offset) {
>                 if (mmo->mmap_type == I915_MMAP_TYPE_OFFSET_WC ||
>                     mmo->mmap_type == I915_MMAP_TYPE_OFFSET_WB ||
> -                   mmo->mmap_type == I915_MMAP_TYPE_OFFSET_UC)
> +                   mmo->mmap_type == I915_MMAP_TYPE_OFFSET_UC ||
> +                   mmo->mmap_type == I915_MMAP_TYPE_DUMB_WC)

Why even special case it???

Even at three logical-ors I suggest you start encoding flags into
mmap_type.

In this case, why isn't it something like

if (has_node(&mmo->vma_node))
>                         drm_vma_node_unmap(&mmo->vma_node,
>                                            obj->base.dev->anon_inode->i_mapping);

>         }
> @@ -602,6 +603,19 @@ __assign_gem_object_mmap_data(struct drm_file *file,
>         return ret;
>  }
>  
> +int
> +i915_gem_mmap_dumb(struct drm_file *file,
> +                 struct drm_device *dev,
> +                 u32 handle,
> +                 u64 *offset)
> +{
> +       struct drm_i915_private *i915 = dev->dev_private;
> +       enum i915_mmap_type mmap_type = HAS_MAPPABLE_APERTURE(i915) ?
> +               I915_MMAP_TYPE_GTT : I915_MMAP_TYPE_DUMB_WC;

It's a linear buffer, you can always do WC now that you can return an
offset for WC.

> +
> +       return __assign_gem_object_mmap_data(file, handle, mmap_type, offset);
> +}
> +
>  /**
>   * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
>   * @dev: DRM device
> @@ -714,6 +728,7 @@ static void set_vmdata_mmap_offset(struct i915_mmap_offset *mmo, struct vm_area_
>  {
>         switch (mmo->mmap_type) {
>         case I915_MMAP_TYPE_OFFSET_WC:
> +       case I915_MMAP_TYPE_DUMB_WC:
>                 vma->vm_page_prot =
>                         pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>                 break;
> @@ -801,6 +816,7 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>         case I915_MMAP_TYPE_OFFSET_WC:
>         case I915_MMAP_TYPE_OFFSET_WB:
>         case I915_MMAP_TYPE_OFFSET_UC:
> +       case I915_MMAP_TYPE_DUMB_WC:

Yup, that was quite redundant.