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
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@ -310,6 +310,17 @@ created.
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Drivers that want to map the GEM object upfront instead of handling page
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faults can implement their own mmap file operation handler.
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For platforms without MMU the GEM core provides a helper method
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:c:func:`drm_gem_cma_get_unmapped_area`. The mmap() routines will call
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this to get a proposed address for the mapping.
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To use :c:func:`drm_gem_cma_get_unmapped_area`, drivers must fill the
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struct :c:type:`struct file_operations <file_operations>` get_unmapped_area
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field with a pointer on :c:func:`drm_gem_cma_get_unmapped_area`.
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More detailed information about get_unmapped_area can be found in
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Documentation/nommu-mmap.txt
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Memory Coherency
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----------------
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@ -6,7 +6,7 @@
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#
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menuconfig DRM
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tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
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depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU && HAS_DMA
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depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
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select HDMI
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select FB_CMDLINE
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select I2C
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@ -113,7 +113,7 @@ config DRM_LOAD_EDID_FIRMWARE
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config DRM_TTM
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tristate
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depends on DRM
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depends on DRM && MMU
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help
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GPU memory management subsystem for devices with multiple
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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)
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}
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EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
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#ifndef CONFIG_MMU
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/**
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* drm_gem_cma_get_unmapped_area - propose address for mapping in noMMU cases
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* @filp: file object
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* @addr: memory address
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* @len: buffer size
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* @pgoff: page offset
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* @flags: memory flags
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*
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* This function is used in noMMU platforms to propose address mapping
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* for a given buffer.
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* It's intended to be used as a direct handler for the struct
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* &file_operations.get_unmapped_area operation.
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*
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* Returns:
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* mapping address on success or a negative error code on failure.
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*/
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unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags)
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{
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struct drm_gem_cma_object *cma_obj;
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struct drm_gem_object *obj = NULL;
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struct drm_file *priv = filp->private_data;
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struct drm_device *dev = priv->minor->dev;
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struct drm_vma_offset_node *node;
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if (drm_device_is_unplugged(dev))
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return -ENODEV;
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drm_vma_offset_lock_lookup(dev->vma_offset_manager);
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node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
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pgoff,
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len >> PAGE_SHIFT);
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if (likely(node)) {
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obj = container_of(node, struct drm_gem_object, vma_node);
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/*
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* When the object is being freed, after it hits 0-refcnt it
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* proceeds to tear down the object. In the process it will
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* attempt to remove the VMA offset and so acquire this
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* mgr->vm_lock. Therefore if we find an object with a 0-refcnt
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* that matches our range, we know it is in the process of being
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* destroyed and will be freed as soon as we release the lock -
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* so we have to check for the 0-refcnted object and treat it as
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* invalid.
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*/
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if (!kref_get_unless_zero(&obj->refcount))
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obj = NULL;
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}
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drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
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if (!obj)
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return -EINVAL;
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if (!drm_vma_node_is_allowed(node, priv)) {
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drm_gem_object_unreference_unlocked(obj);
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return -EACCES;
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}
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cma_obj = to_drm_gem_cma_obj(obj);
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drm_gem_object_unreference_unlocked(obj);
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return cma_obj->vaddr ? (unsigned long)cma_obj->vaddr : -EINVAL;
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}
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EXPORT_SYMBOL_GPL(drm_gem_cma_get_unmapped_area);
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#endif
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#ifdef CONFIG_DEBUG_FS
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/**
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* 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,
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extern const struct vm_operations_struct drm_gem_cma_vm_ops;
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#ifndef CONFIG_MMU
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unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags);
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#else
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static inline unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags)
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{
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return -EINVAL;
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}
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#endif
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#ifdef CONFIG_DEBUG_FS
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void drm_gem_cma_describe(struct drm_gem_cma_object *obj, struct seq_file *m);
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#endif
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