CMA连续物理内存用户空间映射---(一)

2023-01-09 18:50:41

背景：

在多媒体和图像处理等应用中，经经常使用到大块内存，尤其是硬件编解码。须要内核分配大块的物理连续内存。

这里希望通过把从内核分配的连续物理内存映射到用户空间。在用户空间经过处理，又能够入队到驱动中。

前提：

Kernel Config中依据需求配置和调整CMA的大小。

方法：

（一）

1、驱动注冊misc设备。

2、驱动实现IOCTL的内存分配，使用dma_alloc_writecombine从CMA中拿出一个内存。

3、驱动实现mmap，通过remap_pfn_range，把上面第二步dma分配到的物理内存映射到用户空间；

（二）

1、用户打开设备节点/dev/cma_mem；

2、通过ioctl命令，设置须要分配的大小。

3、通过mmap映射；

測试环境：

Linux-3.9.7

arm-linux-gcc 4.5.1

s5pv210

源代码：

驱动

cma_mem.c

#include <linux/miscdevice.h>

#include <linux/platform_device.h>

#include <linux/fs.h>

#include <linux/file.h>

#include <linux/mm.h>

#include <linux/list.h>

#include <linux/mutex.h>

#include <linux/debugfs.h>

#include <linux/mempolicy.h>

#include <linux/sched.h>

#include <linux/module.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <asm/cacheflush.h>

#include <linux/dma-mapping.h>

#include <linux/export.h>

#include "cma_mem.h"

#define DEVICE_NAME "cma_mem" 

enum cma_status{

	UNKNOW_STATUS = 0,

	HAVE_ALLOCED = 1,

	HAVE_MMAPED =2,

};

struct cmamem_dev {

	unsigned int count;

	struct miscdevice dev;

	struct mutex cmamem_lock;

	struct list_head info_list;

};

struct current_status{

		int status;

		int id_count;

		dma_addr_t phy_base;

};

static struct current_status cmamem_status;

static struct cmamem_dev cmamem_dev;

static struct cmamem_info cma_info[32];

static long cmamem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

{

	int ret = 0;

	int size = 0;

	dma_addr_t map_dma;

	switch(cmd){

		case CMEM_ALLOCATE:

		{

			printk(KERN_ERR"cmamem_ioctl:CMEM_ALLOCATE\n");

			cmamem_status.id_count = cmamem_dev.count++;

			cma_info[cmamem_status.id_count].id = cmamem_status.id_count;

			if ((ret = copy_from_user(&cma_info[cmamem_status.id_count], (void __user *)arg,

			sizeof(struct cmamem_info))))

			{

				printk(KERN_ERR"cmamem_ioctl:CMEM_ALLOCATE:copy_from_user error:%d\n", ret);

				ret = -EFAULT;

				goto err;

			}

			size = cma_info[cmamem_status.id_count].len;

			size = PAGE_ALIGN(size);

			if(size == 0)

			{

				printk(KERN_ERR"size is 0\n");

				ret = -ENOMEM;

				goto err;

			}

			printk(KERN_ERR"cmamem_ioctl:CMEM_ALLOCATE:start alloc:%d,size:%d\n", cmamem_status.id_count, cma_info[cmamem_status.id_count].len);

			cma_info[cmamem_status.id_count].mem_base = (unsigned int)dma_alloc_writecombine(NULL, size, &map_dma, GFP_KERNEL);

			if (!cma_info[cmamem_status.id_count].mem_base){

				printk(KERN_ERR "dma alloc fail:%d!\n", __LINE__);

				ret = -ENOMEM;

				goto err;

			}

			printk(KERN_ERR"map_dma:0x%08x,size:%d\n", map_dma, size);

			cma_info[cmamem_status.id_count].phy_base = map_dma;

			cmamem_status.phy_base = map_dma;

			mutex_lock(&cmamem_dev.cmamem_lock);

			cmamem_status.status = HAVE_ALLOCED;

			mutex_unlock(&cmamem_dev.cmamem_lock);

			break;

		}

		default:

		{

			printk(KERN_INFO "cma mem not support command\n");

			break;

		}

	}

	err:

	return ret;

}

static int cmamem_mmap(struct file *filp, struct vm_area_struct *vma)

{

	unsigned long start = vma->vm_start;

	unsigned long size = vma->vm_end - vma->vm_start;

	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;

	unsigned long page, pos;

	//dump_stack();

	if(cmamem_status.status != HAVE_ALLOCED)

	{

		printk(KERN_ERR"%s, you should allocted memory firstly\n", __func__);

		return -EINVAL;

	}

	printk( "start=0x%08x offset=0x%08x\n", (unsigned int)start, (unsigned int)offset );

	pos = (unsigned long)cmamem_status.phy_base + offset;

	page = pos >> PAGE_SHIFT ;

	if( remap_pfn_range( vma, start, page, size, PAGE_SHARED )) {

		return -EAGAIN;

	}

	else{

		printk( "remap_pfn_range %u\n success\n", (unsigned int)page );

	}

	vma->vm_flags &= ~VM_IO;

	vma->vm_flags |=  (VM_DONTEXPAND | VM_DONTDUMP);

	return 0;

}

static struct file_operations dev_fops = {

    .owner          = THIS_MODULE,

    .unlocked_ioctl = cmamem_ioctl,

	.mmap = cmamem_mmap,

};

static int __init cmamem_init(void)

{

	printk(KERN_ERR"%s\n", __func__);

	mutex_init(&cmamem_dev.cmamem_lock);

	INIT_LIST_HEAD(&cmamem_dev.info_list);

	cmamem_dev.count = 0;

	cmamem_dev.dev.name = DEVICE_NAME;

	cmamem_dev.dev.minor = MISC_DYNAMIC_MINOR;

	cmamem_dev.dev.fops = &dev_fops;

	cmamem_status.status = UNKNOW_STATUS;

	cmamem_status.id_count = -1;

	cmamem_status.phy_base = 0;

	return misc_register(&cmamem_dev.dev);

}

static void __exit cmamem_exit(void)

{

    printk(KERN_ERR"%s\n", __func__);

	misc_deregister(&cmamem_dev.dev);

} 

module_init(cmamem_init);

module_exit(cmamem_exit);

MODULE_LICENSE("GPL");

cma_mem.h

#ifndef _CMA_MEM_H_

#define _CMA_MEM_H_

#define CMEM_IOCTL_MAGIC 'm'

#define CMEM_GET_PHYS		_IOW(CMEM_IOCTL_MAGIC, 1, unsigned int)

#define CMEM_MAP		_IOW(CMEM_IOCTL_MAGIC, 2, unsigned int)

#define CMEM_GET_SIZE		_IOW(CMEM_IOCTL_MAGIC, 3, unsigned int)

#define CMEM_UNMAP		_IOW(CMEM_IOCTL_MAGIC, 4, unsigned int)

#define CMEM_ALLOCATE		_IOW(CMEM_IOCTL_MAGIC, 5, unsigned int)

#define CMEM_CONNECT		_IOW(CMEM_IOCTL_MAGIC, 6, unsigned int)

#define CMEM_GET_TOTAL_SIZE	_IOW(CMEM_IOCTL_MAGIC, 7, unsigned int)

#define CMEM_CACHE_FLUSH	_IOW(CMEM_IOCTL_MAGIC, 8, unsigned int)

struct cmamem_info {

	char *name;

	char is_cache;

	unsigned int id;

	unsigned int offset;

	unsigned int len;

	unsigned int phy_base;

	unsigned int mem_base;

//	struct list_head list;

};

#endif

Makefile

KERN_DIR = /work/kernel/linux-3.9.7

all:

	make -C $(KERN_DIR) M=`pwd` modules 

clean:

	make -C $(KERN_DIR) M=`pwd` modules clean

	rm -rf modules.order

obj-m	+= cma_mem.o

用户測试程序

#include <stdio.h>

#include <stdarg.h>

#include <string.h>

#include <errno.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <time.h>

#include <sys/mman.h>

#include <assert.h>

#include <linux/videodev2.h>

#include <linux/fb.h>

#include <pthread.h>

#include <poll.h>

#include <semaphore.h>

#define CMEM_IOCTL_MAGIC 'm'

#define CMEM_GET_PHYS		_IOW(CMEM_IOCTL_MAGIC, 1, unsigned int)

#define CMEM_MAP		_IOW(CMEM_IOCTL_MAGIC, 2, unsigned int)

#define CMEM_GET_SIZE		_IOW(CMEM_IOCTL_MAGIC, 3, unsigned int)

#define CMEM_UNMAP		_IOW(CMEM_IOCTL_MAGIC, 4, unsigned int)

#define CMEM_ALLOCATE		_IOW(CMEM_IOCTL_MAGIC, 5, unsigned int)

#define CMEM_CONNECT		_IOW(CMEM_IOCTL_MAGIC, 6, unsigned int)

#define CMEM_GET_TOTAL_SIZE	_IOW(CMEM_IOCTL_MAGIC, 7, unsigned int)

#define CMEM_CACHE_FLUSH	_IOW(CMEM_IOCTL_MAGIC, 8, unsigned int)

struct cmamem_info {

	char *name;

	char is_cache;

	unsigned long id;

	unsigned long offset;

	unsigned long len;

	unsigned long phy_base;

	unsigned long mem_base;

//	struct list_head list;

};

int main()

{

	int cmem_fd;

	void *cmem_base;

	unsigned int size;

	struct cmamem_info region;

	int i;

	cmem_fd = open("/dev/cma_mem", O_RDWR, 0);//打开设备。为了操作硬件引擎，要noncache的

	printf("cmem_fd:%d\n", cmem_fd);

	if (cmem_fd >= 0)

	{       

		memset(&region, 0x00, sizeof(struct cmamem_info));

		region.len = 800 * 480 * 4;

		if (ioctl(cmem_fd, CMEM_ALLOCATE, &region) < 0) //获取所有空间

		{

			perror("PMEM_GET_TOTAL_SIZE failed\n");

			return -1;

		}

		size = region.len;

		cmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, cmem_fd, 0);//mmap操作

		printf("cmem_base:0x%08x,region.len:0x%08x offset:0x%08x\n",(unsigned int)cmem_base, region.len, region.offset);

		if (cmem_base == MAP_FAILED)

		{	cmem_base = 0;

            close(cmem_fd);

            cmem_fd = -1;

			perror("mmap pmem error!\n");

		}

		for(i = 0; i < 10; i++)

		((unsigned int *)cmem_base)[i] = i;

		printf("pmem_base:0x%08x\n", cmem_base);

		for(i = 0; i < 10; i++)

		printf("%d\n", ((unsigned int *)cmem_base)[i]);

    }

	close(cmem_fd);

	return 0;

}

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