SHMEM-buffer backing storage is allocated from system memory; which is
typically cachable. Currently, only virtio uses cachable mappings; udl
uses its own vmap/mmap implementation for cachable mappings. Other
drivers default to writecombine mappings.
Use cached mappings by default. The exception is pages imported via
dma-buf. DMA memory is usually not cached.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 6 ++++--
drivers/gpu/drm/virtio/virtgpu_object.c | 1 -
include/drm/drm_gem_shmem_helper.h | 4 ++--
3 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index df31e5782eed1..1ce90325dfa31 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -259,7 +259,7 @@ static void *drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem)
} else {
pgprot_t prot = PAGE_KERNEL;
- if (!shmem->map_cached)
+ if (shmem->map_wc)
prot = pgprot_writecombine(prot);
shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
VM_MAP, prot);
@@ -546,7 +546,7 @@ 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 = vm_get_page_prot(vma->vm_flags);
- if (!shmem->map_cached)
+ if (shmem->map_wc)
vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
vma->vm_ops = &drm_gem_shmem_vm_ops;
@@ -664,6 +664,8 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
if (IS_ERR(shmem))
return ERR_CAST(shmem);
+ shmem->map_wc = false; /* dma-buf mappings use writecombine */
+
shmem->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
if (!shmem->pages) {
ret = -ENOMEM;
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 6ccbd01cd888c..80ba6b2b61668 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -132,7 +132,6 @@ struct drm_gem_object *virtio_gpu_create_object(struct drm_device *dev,
dshmem = &shmem->base.base;
dshmem->base.funcs = &virtio_gpu_shmem_funcs;
- dshmem->map_cached = true;
return &dshmem->base;
}
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 294b2931c4cc0..a5bc082a77c48 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -98,9 +98,9 @@ struct drm_gem_shmem_object {
unsigned int vmap_use_count;
/**
- * @map_cached: map object cached (instead of using writecombine).
+ * @map_wc: map object using writecombine (instead of cached).
*/
- bool map_cached;
+ bool map_wc;
};
#define to_drm_gem_shmem_obj(obj) \
--
2.26.2
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