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Subject[PATCH v2 1/2] drm/shmem: add support for per object caching attributes
Date
Add caching field to drm_gem_shmem_object to specify the cachine
attributes for mappings. Add helper function to tweak pgprot
accordingly. Switch vmap and mmap functions to the new helper.

Set caching to write-combine when creating the object so behavior
doesn't change by default. Drivers can override that later if
needed.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
include/drm/drm_gem_shmem_helper.h | 12 ++++++++++++
drivers/gpu/drm/drm_gem_shmem_helper.c | 24 +++++++++++++++++++++---
2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 6748379a0b44..9d6e02c6205f 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -17,6 +17,11 @@ struct drm_mode_create_dumb;
struct drm_printer;
struct sg_table;

+enum drm_gem_shmem_caching {
+ DRM_GEM_SHMEM_CACHED = 1,
+ DRM_GEM_SHMEM_WC,
+};
+
/**
* struct drm_gem_shmem_object - GEM object backed by shmem
*/
@@ -83,6 +88,11 @@ struct drm_gem_shmem_object {
* The address are un-mapped when the count reaches zero.
*/
unsigned int vmap_use_count;
+
+ /**
+ * @caching: caching attributes for mappings.
+ */
+ enum drm_gem_shmem_caching caching;
};

#define to_drm_gem_shmem_obj(obj) \
@@ -130,6 +140,8 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,

struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj);

+pgprot_t drm_gem_shmem_caching(struct drm_gem_shmem_object *shmem, pgprot_t prot);
+
/**
* DRM_GEM_SHMEM_DRIVER_OPS - Default shmem GEM operations
*
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index a421a2eed48a..5bb94e130a50 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -76,6 +76,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
mutex_init(&shmem->pages_lock);
mutex_init(&shmem->vmap_lock);
INIT_LIST_HEAD(&shmem->madv_list);
+ shmem->caching = DRM_GEM_SHMEM_WC;

/*
* Our buffers are kept pinned, so allocating them
@@ -256,9 +257,11 @@ 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 = drm_gem_shmem_caching(shmem, PAGE_KERNEL);
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 +543,8 @@ 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);
+ vma->vm_page_prot = drm_gem_shmem_caching(shmem, vma->vm_page_prot);
vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
vma->vm_ops = &drm_gem_shmem_vm_ops;

@@ -683,3 +687,17 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
+
+pgprot_t drm_gem_shmem_caching(struct drm_gem_shmem_object *shmem, pgprot_t prot)
+{
+ switch (shmem->caching) {
+ case DRM_GEM_SHMEM_CACHED:
+ return prot;
+ case DRM_GEM_SHMEM_WC:
+ return pgprot_writecombine(prot);
+ default:
+ WARN_ON_ONCE(1);
+ return prot;
+ }
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_caching);
--
2.18.1
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