linux-kernel - [PATCH v4 1/3] drm/shmem: add support for per object caching flags.

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Date:   Wed, 18 Dec 2019 13:56:43 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     tzimmermann@...e.de, gurchetansingh@...omium.org,
        Gerd Hoffmann <kraxel@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v4 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.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 include/drm/drm_gem_shmem_helper.h     |  5 +++++
 drivers/gpu/drm/drm_gem_shmem_helper.c | 12 +++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 6748379a0b44..e69f58d467c6 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -83,6 +83,11 @@ 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..443265a4fc5a 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -256,9 +256,13 @@ static void *drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem)
 
 	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 +544,9 @@ 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;
 
-- 
2.18.1