RE: [PATCH v5 1/3] drm/shmem: add support for per object caching flags.

[Guillaume Gardet <Guillaume.Gardet@arm.com>]

> -----Original Message-----
> From: Gerd Hoffmann <kraxel@redhat.com>
> Sent: 26 February 2020 16:48
> To: dri-devel@lists.freedesktop.org
> Cc: tzimmermann@suse.de; gurchetansingh@chromium.org; olvaffe@gmail.com;
> Guillaume Gardet <Guillaume.Gardet@arm.com>; Gerd Hoffmann
> <kraxel@redhat.com>; stable@vger.kernel.org; Maarten Lankhorst
> <maarten.lankhorst@linux.intel.com>; Maxime Ripard <mripard@kernel.org>;
> David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; open list <linux-
> kernel@vger.kernel.org>
> Subject: [PATCH v5 1/3] drm/shmem: add support for per object caching flags.
>
> Add map_cached bool to drm_gem_shmem_object, to request cached mappings
> on a per-object base.  Check the flag before adding writecombine to pgprot bits.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Tested-by: Guillaume Gardet <Guillaume.Gardet@arm.com>

> ---
>  include/drm/drm_gem_shmem_helper.h     |  5 +++++
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 15 +++++++++++----
>  2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/include/drm/drm_gem_shmem_helper.h
> b/include/drm/drm_gem_shmem_helper.h
> index e34a7b7f848a..294b2931c4cc 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -96,6 +96,11 @@ struct drm_gem_shmem_object {
>   * The address are un-mapped when the count reaches zero.
>   */
>  unsigned int vmap_use_count;
> +
> +/**
> + * @map_cached: map object cached (instead of using writecombine).
> + */
> +bool map_cached;
>  };
>
>  #define to_drm_gem_shmem_obj(obj) \
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index a421a2eed48a..aad9324dcf4f 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -254,11 +254,16 @@ static void *drm_gem_shmem_vmap_locked(struct
> drm_gem_shmem_object *shmem)
>  if (ret)
>  goto err_zero_use;
>
> -if (obj->import_attach)
> +if (obj->import_attach) {
>  shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
> -else
> +} else {
> +pgprot_t prot = PAGE_KERNEL;
> +
> +if (!shmem->map_cached)
> +prot = pgprot_writecombine(prot);
>  shmem->vaddr = vmap(shmem->pages, obj->size >>
> PAGE_SHIFT,
> -    VM_MAP,
> pgprot_writecombine(PAGE_KERNEL));
> +    VM_MAP, prot);
> +}
>
>  if (!shmem->vaddr) {
>  DRM_DEBUG_KMS("Failed to vmap pages\n"); @@ -540,7 +545,9
> @@ int drm_gem_shmem_mmap(struct drm_gem_object *obj, struct
> vm_area_struct *vma)
>  }
>
>  vma->vm_flags |= VM_MIXEDMAP | VM_DONTEXPAND;
> -vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma-
> >vm_flags));
> +vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> +if (!shmem->map_cached)
> +vma->vm_page_prot = pgprot_writecombine(vma-
> >vm_page_prot);
>  vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>  vma->vm_ops = &drm_gem_shmem_vm_ops;
>
> --
> 2.18.2

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