[PATCH v2 3/5] drm: Add and export function drm_gem_cma_mmap_noncoherent

Paul Cercueil
2021-03-07T20:30:08Z

This function can be used by drivers that need to mmap dumb buffers
created with non-coherent backing memory.

v2: Use dma_to_phys() since cma_obj->paddr isn't a phys_addr_t but a
dma_addr_t.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
drivers/gpu/drm/drm_gem_cma_helper.c | 67 +++++++++++++++++++++++++---
include/drm/drm_gem_cma_helper.h | 1 +
2 files changed, 63 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index d100c5f9c140..e39b0464e19d 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -10,6 +10,7 @@
*/

#include <linux/dma-buf.h>
+#include <linux/dma-direct.h>
#include <linux/dma-mapping.h>
#include <linux/export.h>
#include <linux/mm.h>
@@ -42,10 +43,20 @@ static const struct drm_gem_object_funcs drm_gem_cma_default_funcs = {
.vm_ops = &drm_gem_cma_vm_ops,
};

+static const struct drm_gem_object_funcs drm_gem_cma_noncoherent_funcs = {
+ .free = drm_gem_cma_free_object,
+ .print_info = drm_gem_cma_print_info,
+ .get_sg_table = drm_gem_cma_get_sg_table,
+ .vmap = drm_gem_cma_vmap,
+ .mmap = drm_gem_cma_mmap_noncoherent,
+ .vm_ops = &drm_gem_cma_vm_ops,
+};
+
/**
* __drm_gem_cma_create - Create a GEM CMA object without allocating memory
* @drm: DRM device
* @size: size of the object to allocate
+ * @noncoherent: if true, will use non-coherent backed memory
*
* This function creates and initializes a GEM CMA object of the given size,
* but doesn't allocate any memory to back the object.
@@ -55,7 +66,7 @@ static const struct drm_gem_object_funcs drm_gem_cma_default_funcs = {
* error code on failure.
*/
static struct drm_gem_cma_object *
-__drm_gem_cma_create(struct drm_device *drm, size_t size)
+__drm_gem_cma_create(struct drm_device *drm, size_t size, bool noncoherent)
{
struct drm_gem_cma_object *cma_obj;
struct drm_gem_object *gem_obj;
@@ -68,8 +79,12 @@ __drm_gem_cma_create(struct drm_device *drm, size_t size)
if (!gem_obj)
return ERR_PTR(-ENOMEM);

- if (!gem_obj->funcs)
- gem_obj->funcs = &drm_gem_cma_default_funcs;
+ if (!gem_obj->funcs) {
+ if (noncoherent)
+ gem_obj->funcs = &drm_gem_cma_noncoherent_funcs;
+ else
+ gem_obj->funcs = &drm_gem_cma_default_funcs;
+ }

cma_obj = container_of(gem_obj, struct drm_gem_cma_object, base);

@@ -100,7 +115,7 @@ drm_gem_cma_create_with_cache_param(struct drm_device *drm,

size = round_up(size, PAGE_SIZE);

- cma_obj = __drm_gem_cma_create(drm, size);
+ cma_obj = __drm_gem_cma_create(drm, size, noncoherent);
if (IS_ERR(cma_obj))
return cma_obj;

@@ -503,7 +518,7 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
return ERR_PTR(-EINVAL);

/* Create a CMA GEM buffer. */
- cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size);
+ cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size, false);
if (IS_ERR(cma_obj))
return ERR_CAST(cma_obj);

@@ -579,6 +594,48 @@ int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
}
EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);

+/**
+ * drm_gem_cma_mmap_noncoherent - memory-map a CMA GEM object with
+ * non-coherent cache attribute
+ * @filp: file object
+ * @vma: VMA for the area to be mapped
+ *
+ * Just like drm_gem_cma_mmap, but for a GEM object backed by non-coherent
+ * memory.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_cma_mmap_noncoherent(struct drm_gem_object *obj,
+ struct vm_area_struct *vma)
+{
+ struct drm_gem_cma_object *cma_obj;
+ unsigned long pfn;
+ int ret;
+
+ /*
+ * Clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
+ * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
+ * the whole buffer.
+ */
+ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
+ vma->vm_flags &= ~VM_PFNMAP;
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+
+ cma_obj = to_drm_gem_cma_obj(obj);
+
+ pfn = PHYS_PFN(dma_to_phys(cma_obj->base.dev->dev, cma_obj->paddr));
+
+ ret = remap_pfn_range(vma, vma->vm_start, pfn,
+ vma->vm_end - vma->vm_start,
+ vma->vm_page_prot);
+ if (ret)
+ drm_gem_vm_close(vma);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_cma_mmap_noncoherent);
+
/**
* drm_gem_cma_prime_import_sg_table_vmap - PRIME import another driver's
* scatter/gather table and get the virtual address of the buffer
diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
index 6b44e7492a63..6a3f7e1312cc 100644
--- a/include/drm/drm_gem_cma_helper.h
+++ b/include/drm/drm_gem_cma_helper.h
@@ -107,6 +107,7 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
struct sg_table *sgt);
int drm_gem_cma_vmap(struct drm_gem_object *obj, struct dma_buf_map *map);
int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma);
+int drm_gem_cma_mmap_noncoherent(struct drm_gem_object *obj, struct vm_area_struct *vma);

/**
* DRM_GEM_CMA_DRIVER_OPS_WITH_DUMB_CREATE - CMA GEM driver operations
--
2.30.1