[PATCH v4] DRM: add drm gem CMA helper

[Laurent Pinchart]

Hi Sascha,

On Wednesday 27 June 2012 15:30:18 Sascha Hauer wrote:
> Many embedded drm devices do not have a IOMMU and no dedicated
> memory for graphics. These devices use CMA (Contiguous Memory
> Allocator) backed graphics memory. This patch provides helper
> functions to be able to share the code. The code technically does
> not depend on CMA as the backend allocator, the name has been chosen
> because cma makes for a nice, short but still descriptive function
> prefix.
> 
> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> ---
> 
> changes since v3:
> - *really* use DIV_ROUND_UP(args->width * args->bpp, 8) to calculate the
> pitch changes since v2:
> - make drm_gem_cma_create_with_handle static
> - use DIV_ROUND_UP(args->width * args->bpp, 8) to calculate the pitch
> - make drm_gem_cma_vm_ops const
> - add missing #include <linux/export.h>
> changes since v1:
> - map whole buffer at mmap time, not page by page at fault time
> - several cleanups as suggested by Lars-Peter Clausen and Laurent Pinchart
> 
>  drivers/gpu/drm/Kconfig              |    6 +
>  drivers/gpu/drm/Makefile             |    1 +
>  drivers/gpu/drm/drm_gem_cma_helper.c |  251 +++++++++++++++++++++++++++++++
>  include/drm/drm_gem_cma_helper.h     |   44 ++++++
>  4 files changed, 302 insertions(+)
>  create mode 100644 drivers/gpu/drm/drm_gem_cma_helper.c
>  create mode 100644 include/drm/drm_gem_cma_helper.h
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index dc5df12..8f362ec 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -53,6 +53,12 @@ config DRM_TTM
>  	  GPU memory types. Will be enabled automatically if a device driver
>  	  uses it.
> 
> +config DRM_GEM_CMA_HELPER
> +	tristate
> +	depends on DRM
> +	help
> +	  Choose this if you need the GEM CMA helper functions
> +
>  config DRM_TDFX
>  	tristate "3dfx Banshee/Voodoo3+"
>  	depends on DRM && PCI
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 0487ff6..8759cda 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -15,6 +15,7 @@ drm-y       :=	drm_auth.o drm_buffer.o drm_bufs.o
> drm_cache.o \ drm_trace_points.o drm_global.o drm_prime.o
> 
>  drm-$(CONFIG_COMPAT) += drm_ioc32.o
> +drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o

This results in a built failure for me with

CONFIG_DRM=y
CONFIG_DRM_KMS_HELPER=m
# CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
CONFIG_DRM_GEM_CMA_HELPER=m
CONFIG_DRM_KMS_CMA_HELPER=m

drm_gem_cma_helper.o isn't compiled at all. Can you reproduce the problem ?

>  drm-usb-y   := drm_usb.o
> 
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
> b/drivers/gpu/drm/drm_gem_cma_helper.c new file mode 100644
> index 0000000..1aa8fee
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -0,0 +1,251 @@
> +/*
> + * drm gem CMA (contiguous memory allocator) helper functions
> + *
> + * Copyright (C) 2012 Sascha Hauer, Pengutronix
> + *
> + * Based on Samsung Exynos code
> + *
> + * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/mutex.h>
> +#include <linux/export.h>
> +#include <linux/dma-mapping.h>
> +
> +#include <drm/drmP.h>
> +#include <drm/drm.h>
> +#include <drm/drm_gem_cma_helper.h>
> +
> +static unsigned int get_gem_mmap_offset(struct drm_gem_object *obj)
> +{
> +	return (unsigned int)obj->map_list.hash.key << PAGE_SHIFT;
> +}
> +
> +static void drm_gem_cma_buf_destroy(struct drm_device *drm,
> +		struct drm_gem_cma_object *cma_obj)
> +{
> +	dma_free_writecombine(drm->dev, cma_obj->base.size, cma_obj->vaddr,
> +			cma_obj->paddr);
> +}
> +
> +/*
> + * drm_gem_cma_create - allocate an object with the given size
> + *
> + * returns a struct drm_gem_cma_object* on success or ERR_PTR values
> + * on failure.
> + */
> +struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
> +		unsigned int size)
> +{
> +	struct drm_gem_cma_object *cma_obj;
> +	struct drm_gem_object *gem_obj;
> +	int ret;
> +
> +	size = round_up(size, PAGE_SIZE);
> +
> +	cma_obj = kzalloc(sizeof(*cma_obj), GFP_KERNEL);
> +	if (!cma_obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	cma_obj->vaddr = dma_alloc_writecombine(drm->dev, size,
> +			&cma_obj->paddr, GFP_KERNEL | __GFP_NOWARN);
> +	if (!cma_obj->vaddr) {
> +		dev_err(drm->dev, "failed to allocate buffer with size %d\n", size);
> +		ret = -ENOMEM;
> +		goto err_dma_alloc;
> +	}
> +
> +	gem_obj = &cma_obj->base;
> +
> +	ret = drm_gem_object_init(drm, gem_obj, size);
> +	if (ret)
> +		goto err_obj_init;
> +
> +	ret = drm_gem_create_mmap_offset(gem_obj);
> +	if (ret)
> +		goto err_create_mmap_offset;
> +
> +	return cma_obj;
> +
> +err_create_mmap_offset:
> +	drm_gem_object_release(gem_obj);
> +
> +err_obj_init:
> +	drm_gem_cma_buf_destroy(drm, cma_obj);
> +
> +err_dma_alloc:
> +	kfree(cma_obj);
> +
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_create);
> +
> +/*
> + * drm_gem_cma_create_with_handle - allocate an object with the given
> + * size and create a gem handle on it
> + *
> + * returns a struct drm_gem_cma_object* on success or ERR_PTR values
> + * on failure.
> + */
> +static struct drm_gem_cma_object *drm_gem_cma_create_with_handle(
> +		struct drm_file *file_priv,
> +		struct drm_device *drm, unsigned int size,
> +		unsigned int *handle)
> +{
> +	struct drm_gem_cma_object *cma_obj;
> +	struct drm_gem_object *gem_obj;
> +	int ret;
> +
> +	cma_obj = drm_gem_cma_create(drm, size);
> +	if (IS_ERR(cma_obj))
> +		return cma_obj;
> +
> +	gem_obj = &cma_obj->base;
> +
> +	/*
> +	 * allocate a id of idr table where the obj is registered
> +	 * and handle has the id what user can see.
> +	 */
> +	ret = drm_gem_handle_create(file_priv, gem_obj, handle);
> +	if (ret)
> +		goto err_handle_create;
> +
> +	/* drop reference from allocate - handle holds it now. */
> +	drm_gem_object_unreference_unlocked(gem_obj);
> +
> +	return cma_obj;
> +
> +err_handle_create:
> +	drm_gem_cma_free_object(gem_obj);
> +
> +	return ERR_PTR(ret);
> +}
> +
> +/*
> + * drm_gem_cma_free_object - (struct drm_driver)->gem_free_object callback
> + * function
> + */
> +void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
> +{
> +	struct drm_gem_cma_object *cma_obj;
> +
> +	if (gem_obj->map_list.map)
> +		drm_gem_free_mmap_offset(gem_obj);
> +
> +	drm_gem_object_release(gem_obj);
> +
> +	cma_obj = to_drm_gem_cma_obj(gem_obj);
> +
> +	drm_gem_cma_buf_destroy(gem_obj->dev, cma_obj);
> +
> +	kfree(cma_obj);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_free_object);
> +
> +/*
> + * drm_gem_cma_dumb_create - (struct drm_driver)->dumb_create callback
> + * function
> + *
> + * This aligns the pitch and size arguments to the minimum required. wrap
> + * this into your own function if you need bigger alignment.
> + */
> +int drm_gem_cma_dumb_create(struct drm_file *file_priv,
> +		struct drm_device *dev, struct drm_mode_create_dumb *args)
> +{
> +	struct drm_gem_cma_object *cma_obj;
> +	int min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> +
> +	if (args->pitch < min_pitch)
> +		args->pitch = min_pitch;
> +
> +	if (args->size < args->pitch * args->height)
> +		args->size = args->pitch * args->height;
> +
> +	cma_obj = drm_gem_cma_create_with_handle(file_priv, dev,
> +			args->size, &args->handle);
> +	if (IS_ERR(cma_obj))
> +		return PTR_ERR(cma_obj);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_dumb_create);
> +
> +/*
> + * drm_gem_cma_dumb_map_offset - (struct drm_driver)->dumb_map_offset
> callback + * function
> + */
> +int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
> +		struct drm_device *drm, uint32_t handle, uint64_t *offset)
> +{
> +	struct drm_gem_object *gem_obj;
> +
> +	mutex_lock(&drm->struct_mutex);
> +
> +	gem_obj = drm_gem_object_lookup(drm, file_priv, handle);
> +	if (!gem_obj) {
> +		dev_err(drm->dev, "failed to lookup gem object\n");
> +		mutex_unlock(&drm->struct_mutex);
> +		return -EINVAL;
> +	}
> +
> +	*offset = get_gem_mmap_offset(gem_obj);
> +
> +	drm_gem_object_unreference(gem_obj);
> +
> +	mutex_unlock(&drm->struct_mutex);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_dumb_map_offset);
> +
> +const struct vm_operations_struct drm_gem_cma_vm_ops = {
> +	.open = drm_gem_vm_open,
> +	.close = drm_gem_vm_close,
> +};
> +EXPORT_SYMBOL_GPL(drm_gem_cma_vm_ops);
> +
> +/*
> + * drm_gem_cma_mmap - (struct file_operation)->mmap callback function
> + */
> +int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct drm_gem_object *gem_obj;
> +	struct drm_gem_cma_object *cma_obj;
> +	int ret;
> +
> +	ret = drm_gem_mmap(filp, vma);
> +	if (ret)
> +		return ret;
> +
> +	gem_obj = vma->vm_private_data;
> +	cma_obj = to_drm_gem_cma_obj(gem_obj);
> +
> +	ret = remap_pfn_range(vma, vma->vm_start, cma_obj->paddr >> PAGE_SHIFT,
> +			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);
> +
> +/*
> + * drm_gem_cma_dumb_destroy - (struct drm_driver)->dumb_destroy callback
> function + */
> +int drm_gem_cma_dumb_destroy(struct drm_file *file_priv,
> +		struct drm_device *drm, unsigned int handle)
> +{
> +	return drm_gem_handle_delete(file_priv, handle);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_dumb_destroy);
> diff --git a/include/drm/drm_gem_cma_helper.h
> b/include/drm/drm_gem_cma_helper.h new file mode 100644
> index 0000000..f0f6b1a
> --- /dev/null
> +++ b/include/drm/drm_gem_cma_helper.h
> @@ -0,0 +1,44 @@
> +#ifndef __DRM_GEM_CMA_HELPER_H__
> +#define __DRM_GEM_CMA_HELPER_H__
> +
> +struct drm_gem_cma_object {
> +	struct drm_gem_object base;
> +	dma_addr_t paddr;
> +	void *vaddr;
> +};
> +
> +static inline struct drm_gem_cma_object *
> +to_drm_gem_cma_obj(struct drm_gem_object *gem_obj)
> +{
> +	return container_of(gem_obj, struct drm_gem_cma_object, base);
> +}
> +
> +/* free gem object. */
> +void drm_gem_cma_free_object(struct drm_gem_object *gem_obj);
> +
> +/* create memory region for drm framebuffer. */
> +int drm_gem_cma_dumb_create(struct drm_file *file_priv,
> +		struct drm_device *drm, struct drm_mode_create_dumb *args);
> +
> +/* map memory region for drm framebuffer to user space. */
> +int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
> +		struct drm_device *drm, uint32_t handle, uint64_t *offset);
> +
> +/* set vm_flags and we can change the vm attribute to other one at here. */
> +int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma); +
> +/*
> + * destroy memory region allocated.
> + *	- a gem handle and physical memory region pointed by a gem object
> + *	would be released by drm_gem_handle_delete().
> + */
> +int drm_gem_cma_dumb_destroy(struct drm_file *file_priv,
> +		struct drm_device *drm, unsigned int handle);
> +
> +/* allocate physical memory. */
> +struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
> +		unsigned int size);
> +
> +extern const struct vm_operations_struct drm_gem_cma_vm_ops;
> +
> +#endif /* __DRM_GEM_CMA_HELPER_H__ */
-- 
Regards,

Laurent Pinchart