drm: allow to use mmuless SoC

Some SoC without MMU have display driver where a drm/kms driver
could be implemented.

Before doing such kind of thing drm/kms must allow to use mmuless devices.
This patch propose to remove MMU configuration flag and add a cma helper
function to help implementing mmuless display driver

version 4:
- add documentation about drm_gem_cma_get_unmapped_area()
- stub it MMU case

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
[danvet: Use recommended struct member references in kernel-doc.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483521177-21794-4-git-send-email-benjamin.gaignard@linaro.org
This commit is contained in:
Benjamin Gaignard 2017-01-04 10:12:57 +01:00 committed by Daniel Vetter
parent 99c48e1e38
commit 62a0d98a18
4 changed files with 101 additions and 2 deletions

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@ -310,6 +310,17 @@ created.
Drivers that want to map the GEM object upfront instead of handling page
faults can implement their own mmap file operation handler.
For platforms without MMU the GEM core provides a helper method
:c:func:`drm_gem_cma_get_unmapped_area`. The mmap() routines will call
this to get a proposed address for the mapping.
To use :c:func:`drm_gem_cma_get_unmapped_area`, drivers must fill the
struct :c:type:`struct file_operations <file_operations>` get_unmapped_area
field with a pointer on :c:func:`drm_gem_cma_get_unmapped_area`.
More detailed information about get_unmapped_area can be found in
Documentation/nommu-mmap.txt
Memory Coherency
----------------

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@ -6,7 +6,7 @@
#
menuconfig DRM
tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU && HAS_DMA
depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
select HDMI
select FB_CMDLINE
select I2C
@ -113,7 +113,7 @@ config DRM_LOAD_EDID_FIRMWARE
config DRM_TTM
tristate
depends on DRM
depends on DRM && MMU
help
GPU memory management subsystem for devices with multiple
GPU memory types. Will be enabled automatically if a device driver

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@ -358,6 +358,77 @@ int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
}
EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
#ifndef CONFIG_MMU
/**
* drm_gem_cma_get_unmapped_area - propose address for mapping in noMMU cases
* @filp: file object
* @addr: memory address
* @len: buffer size
* @pgoff: page offset
* @flags: memory flags
*
* This function is used in noMMU platforms to propose address mapping
* for a given buffer.
* It's intended to be used as a direct handler for the struct
* &file_operations.get_unmapped_area operation.
*
* Returns:
* mapping address on success or a negative error code on failure.
*/
unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
unsigned long addr,
unsigned long len,
unsigned long pgoff,
unsigned long flags)
{
struct drm_gem_cma_object *cma_obj;
struct drm_gem_object *obj = NULL;
struct drm_file *priv = filp->private_data;
struct drm_device *dev = priv->minor->dev;
struct drm_vma_offset_node *node;
if (drm_device_is_unplugged(dev))
return -ENODEV;
drm_vma_offset_lock_lookup(dev->vma_offset_manager);
node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
pgoff,
len >> PAGE_SHIFT);
if (likely(node)) {
obj = container_of(node, struct drm_gem_object, vma_node);
/*
* When the object is being freed, after it hits 0-refcnt it
* proceeds to tear down the object. In the process it will
* attempt to remove the VMA offset and so acquire this
* mgr->vm_lock. Therefore if we find an object with a 0-refcnt
* that matches our range, we know it is in the process of being
* destroyed and will be freed as soon as we release the lock -
* so we have to check for the 0-refcnted object and treat it as
* invalid.
*/
if (!kref_get_unless_zero(&obj->refcount))
obj = NULL;
}
drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
if (!obj)
return -EINVAL;
if (!drm_vma_node_is_allowed(node, priv)) {
drm_gem_object_unreference_unlocked(obj);
return -EACCES;
}
cma_obj = to_drm_gem_cma_obj(obj);
drm_gem_object_unreference_unlocked(obj);
return cma_obj->vaddr ? (unsigned long)cma_obj->vaddr : -EINVAL;
}
EXPORT_SYMBOL_GPL(drm_gem_cma_get_unmapped_area);
#endif
#ifdef CONFIG_DEBUG_FS
/**
* drm_gem_cma_describe - describe a CMA GEM object for debugfs

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@ -53,6 +53,23 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
extern const struct vm_operations_struct drm_gem_cma_vm_ops;
#ifndef CONFIG_MMU
unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
unsigned long addr,
unsigned long len,
unsigned long pgoff,
unsigned long flags);
#else
static inline unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
unsigned long addr,
unsigned long len,
unsigned long pgoff,
unsigned long flags)
{
return -EINVAL;
}
#endif
#ifdef CONFIG_DEBUG_FS
void drm_gem_cma_describe(struct drm_gem_cma_object *obj, struct seq_file *m);
#endif