s3c2440 uda1341声卡驱动分析(目前完全看不懂，努力努力再努力中) 收藏
1，驱动架构：
驱动分两个层次，上层是平台设备驱动，底层是audio驱动与mixer驱动。
（1）标准的平台设备驱动结构，probe与remove两个函数。
probe：
获得平台资源->申请内存区域-io内存重映射->获得并使能时钟->设置gpio口->初始化iis总线-> 初始化uda1341->audio dma初始化->注册dsp和mixer->释放内存区域。
代码及注释：
static int s3c2410iis_probe(struct platform_device *pdev) {
struct resource *res;
unsigned long flags;
int ret;
DPRINTK("s3c2410iis_probe/n");
//获得平台设备资源
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (res == NULL) {
printk(KERN_INFO PFX "failed to get memory region resouce/n");
return -ENOENT;
}
//申请可用内存
res = request_mem_region(res->start, RESSIZE(res), pdev->name);
if(res == 0){
printk(KERN_INFO PFX "failed to request io memory region./n");
return -ENOENT;
}
//io内存重映射
iis_base = ioremap(res->start, RESSIZE(res));
if(iis_base == 0){
printk(KERN_INFO PFX "failed to ioremap() io memory region./n"); ret = -EINVAL;
goto free_mem_region;
}
//获得时钟资源
iis_clock = clk_get(&pdev->dev, "iis");
if (iis_clock == NULL) {
printk(KERN_INFO PFX "failed to find clock source/n");
return -ENOENT;
}
/**************************modify by lfc*****************************/
clk_enable(iis_clock);//使能时钟
/*****************************end add********************************/
//禁用本地中断，gpio口设置，恢复中断
local_irq_save(flags);
/* GPB 4: L3CLOCK, OUTPUT */
s3c2410_gpio_cfgpin(S3C2410_GPB4, S3C2410_GPB4_OUTP);
s3c2410_gpio_pullup(S3C2410_GPB4,1);
/* GPB 3: L3DATA, OUTPUT */
s3c2410_gpio_cfgpin(S3C2410_GPB3,S3C2410_GPB3_OUTP);
/* GPB 2: L3MODE, OUTPUT */
s3c2410_gpio_cfgpin(S3C2410_GPB2,S3C2410_GPB2_OUTP);
s3c2410_gpio_pullup(S3C2410_GPB2,1);
/* GPE 3: I2SSDI */
s3c2410_gpio_cfgpin(S3C2410_GPE3,S3C2410_GPE3_I2SSDI);
s3c2410_gpio_pullup(S3C2410_GPE3,1);
/* GPE 0: I2SLRCK */
s3c2410_gpio_cfgpin(S3C2410_GPE0,S3C2410_GPE0_I2SLRCK);
s3c2410_gpio_pullup(S3C2410_GPE0,1);
/* GPE 1: I2SSCLK */
s3c2410_gpio_cfgpin(S3C2410_GPE1,S3C2410_GPE1_I2SSCLK);
s3c2410_gpio_pullup(S3C2410_GPE1,1);
/* GPE 2: CDCLK */
s3c2410_gpio_cfgpin(S3C2410_GPE2,S3C2410_GPE2_CDCLK);
s3c2410_gpio_pullup(S3C2410_GPE2,1);
/* GPE 4: I2SSDO */
s3c2410_gpio_cfgpin(S3C2410_GPE4,S3C2410_GPE4_I2SSDO);
s3c2410_gpio_pullup(S3C2410_GPE4,1);
local_irq_restore(flags);
init_s3c2410_iis_bus();//初始化iis
init_uda1341();//初始化uda1341
//初始化dma ch1 ch2
output_stream.dma_ch = DMA_CH2;
if (!audio_init_dma(&output_stream, "UDA1341 out") & DMACH_LOW_LEVEL) {
audio_clear_dma(&output_stream,&s3c2410iis_dma_out);
printk( KERN_WARNING AUDIO_NAME_VERBOSE
": unable to get DMA channels/n" );
return -EBUSY;
}
input_stream.dma_ch = DMA_CH1;
if (!audio_init_dma(&input_stream, "UDA1341 in") & DMACH_LOW_LEVEL) {
audio_clear_dma(&input_stream,&s3c2410iis_dma_in);
printk( KERN_WARNING AUDIO_NAME_VERBOSE
": unable to get DMA channels/n" );
return -EBUSY;
}
//注册dsp及mixer
audio_dev_dsp = register_sound_dsp(&smdk2410_audio_fops, -1);
audio_dev_mixer = register_sound_mixer(&smdk2410_mixer_fops, -1);
printk(AUDIO_NAME_VERBOSE " initialized/n");
//释放内存区域
free_mem_region:
release_mem_region(res->start, RESSIZE(res));
return 0;
}
remove:
禁用时钟->取消dsp mixer注册->清除dma
static int s3c2410iis_remove(struct platform_device *dev) {
DPRINTK("s3c2410iis_remove/n");
if (iis_clock != NULL){
clk_disable(iis_clock);
clk_put(iis_clock);
iis_clock = NULL;
}
unregister_sound_dsp(audio_dev_dsp);
unregister_sound_mixer(audio_dev_mixer);
audio_clear_dma(&output_stream,&s3c2410iis_dma_out);
audio_clear_dma(&input_stream,&s3c2410iis_dma_in); /* input */
printk(AUDIO_NAME_VERBOSE " unloaded/n");
return 0;
}
uda1341的初始化：
设置gpio口->uda1341复位->uda1341设置
static void init_uda1341(void)
{
/* GPB 4: L3CLOCK */
/* GPB 3: L3DATA */
/* GPB 2: L3MODE */
unsigned long flags;
DPRINTK("init_uda1341/n");
uda1341_volume = 62 - ((DEF_VOLUME * 61) / 100);
uda1341_boost = 0;
// uda_sampling = DATA2_DEEMP_NONE;
// uda_sampling &= ~(DATA2_MUTE);
local_irq_save(flags);
s3c2410_gpio_setpin(S3C2410_GPB2,1);//L3MODE=1
s3c2410_gpio_setpin(S3C2410_GPB4,1);//L3CLOCK=1
local_irq_restore(flags);
uda1341_l3_address(UDA1341_REG_STATUS);
uda1341_l3_data(0x40 | STAT0_SC_384FS | STAT0_IF_MSB|STAT0_DC_FILTER); // reset uda1341
uda1341_l3_data(STAT1 | STAT1_ADC_ON | STAT1_DAC_ON);
uda1341_l3_address(UDA1341_REG_DATA0);
// uda1341_l3_data(DATA0 |DATA0_VOLUME(0x0)); // maximum volume
uda1341_l3_data(DATA0 | DATA0_VOLUME(uda1341_volume));//lfc
uda1341_l3_data(DATA1 |DATA1_BASS(uda1341_boost)| DATA1_TREBLE(0));
uda1341_l3_data((DATA2 |DATA2_DEEMP_NONE) &~(DATA2_MUTE));
uda1341_l3_data(EXTADDR(EXT2));
uda1341_l3_data(EXTDATA(EXT2_MIC_GAIN(0x6)) | EXT2_MIXMODE_CH1);//input channel 1 select(input channel 2 off)
}
（2）底层的audio和mixer其实就是字符设备，完成file_operations结构体后在上面说的probe函数中注册
audio驱动：
fops结构体
static struct file_operations smdk2410_audio_fops = {
llseek: smdk2410_audio_llseek,
write: smdk2410_audio_write,
read: smdk2410_audio_read,
poll: smdk2410_audio_poll,
ioctl: smdk2410_audio_ioctl,
open: smdk2410_audio_open,
release: smdk2410_audio_release
};
write：
判断打开标志是否可写->判断BUFFER内存空间是否可用->判断阻塞方式还是非阻塞方式->循环写入内存块，并将写好的内存块加入dma队列->返回传输字节数
static ssize_t smdk2410_audio_write(struct file *file, const char *buffer,
size_t count, loff_t * ppos)
{
const char *buffer0 = buffer;
audio_stream_t *s = &output_stream;
int chunksize, ret = 0;
DPRINTK("audio_write : start count=%d/n", count);
switch (file->f_flags & O_ACCMODE) {
case O_WRONLY:
case O_RDWR:
break;
default:
DPRINTK("EPERM/n");
return -EPERM;
}
if (!s->buffers && audio_setup_buf(s)){
DPRINTK("ENOMEM/n");
return -ENOMEM;
}
count &= ~0x03;
while (count > 0) {
audio_buf_t *b = s->buf;
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
if (down_trylock(&b->sem)){
DPRINTK("down_trylock error/n");
break;
}
} else {
ret = -ERESTARTSYS;
if (down_interruptible(&b->sem)){
DPRINTK("down_interruptible error/n");
break;
}
}
if (audio_channels == 2) {//使用双频道
chunksize = s->fragsize - b->size;//当前内存块可供使用空间
if (chunksize > count)
chunksize = count;
DPRINTK("write %d to %d/n", chunksize, s->buf_idx);
if (copy_from_user(b->start + b->size, buffer, chunksize)) {
DPRINTK("copy_from_user error/n");
up(&b->sem);
return -EFAULT;
}
b->size += chunksize;//更新当前内存块的使用情况
} else {//单频道
chunksize = (s->fragsize - b->size) >> 1;
if (chunksize > count)
chunksize = count;
DPRINTK("write %d to %d/n", chunksize*2, s->buf_idx);
if (copy_from_user_mono_stereo(b->start + b->size, buffer, chunksize)) {
DPRINTK("copy_from_user_mono_stereo error/n");
up(&b->sem);
return -EFAULT;
}
b->size += chunksize*2;
}
buffer += chunksize;
count -= chunksize;
if (b->size < s->fragsize) {
up(&b->sem);
break;
}
/* 填满一块内存就交给dma去处理 */
if((ret = s3c2410_dma_enqueue(s->dma_ch, (void *) b, b->dma_addr, b->size))) {
printk("dma enqueue failed./n");
return ret;
}
/* 把内存块加入dma队列后继续填写下一内存块 */
b->size = 0;
NEXT_BUF(s, buf);
}
if ((buffer - buffer0))
ret = buffer - buffer0;//返回已传输的字节数
DPRINTK("audio_write : end count=%d/n/n", ret);
return ret;
}
read:
判断buffer内存空间是否为空，若未空则设置buffer空间，并将buffer内存块放入dma队列->循环将内存块数据读入用户空间->返回读出字节数
static ssize_t smdk2410_audio_read(struct file *file, char *buffer,
size_t count, loff_t * ppos)
{
const char *buffer0 = buffer;
audio_stream_t *s = &input_stream;
int chunksize, ret = 0;
DPRINTK("audio_read: count=%d/n", count);
/*
if (ppos != &file->f_pos)
return -ESPIPE;
*/
if (!s->buffers) {
int i;
if (audio_setup_buf(s))
return -ENOMEM;
for (i = 0; i < s->nbfrags; i++) {
audio_buf_t *b = s->buf;
down(&b->sem);
s3c2410_dma_enqueue(s->dma_ch, (void *) b, b->dma_addr, s->fragsize);
NEXT_BUF(s, buf);
}
}
while (count > 0) {
audio_buf_t *b = s->buf;
/* Wait for a buffer to become full */
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
if (down_trylock(&b->sem))
break;
} else {
ret = -ERESTARTSYS;
if (down_interruptible(&b->sem))
break;
}
chunksize = b->size;
if (chunksize > count)
chunksize = count;
DPRINTK("read %d from %d/n", chunksize, s->buf_idx);
if (copy_to_user(buffer, b->start + s->fragsize - b->size,
chunksize)) {
up(&b->sem);
return -EFAULT;
}
b->size -= chunksize;
buffer += chunksize;
count -= chunksize;
if (b->size > 0) {
up(&b->sem);
break;
}
/* Make current buffer available for DMA again */
s3c2410_dma_enqueue(s->dma_ch, (void *) b, b->dma_addr, s->fragsize);
NEXT_BUF(s, buf);
}
if ((buffer - buffer0))
ret = buffer - buffer0;
// DPRINTK("audio_read: return=%d/n", ret);
return ret;
}
poll:
可读可写两部分判断是否可以无阻塞地读写（buffer信号量为大于0则可以）
static unsigned int smdk2410_audio_poll(struct file *file,struct poll_table_struct *wait)
{
unsigned int mask = 0;
int i;
DPRINTK("audio_poll(): mode=%s/n",
(file->f_mode & FMODE_WRITE) ? "w" : "");
if (file->f_mode & FMODE_READ) {
if (!input_stream.buffers && audio_setup_buf(&input_stream))
return -ENOMEM;
poll_wait(file, &input_stream.buf->wait, wait);
for (i = 0; i < input_stream.nbfrags; i++) {
if (input_stream.buffers[i].sem.count > 0){
mask |= POLLIN | POLLWRNORM;
break;
}
}
}
if (file->f_mode & FMODE_WRITE) {
if (!output_stream.buffers && audio_setup_buf(&output_stream))
return -ENOMEM;
poll_wait(file, &output_stream.buf->wait, wait);
for (i = 0; i < output_stream.nbfrags; i++) {
if (output_stream.buffers[i].sem.count > 0){
mask |= POLLOUT | POLLWRNORM;
break;
}
}
}
DPRINTK("audio_poll() returned mask of %s/n",(mask & POLLOUT) ? "w" : "");
return mask;
}
ioctl:
根据oos audio programe guide完成相应功能
static int smdk2410_audio_ioctl(struct inode *inode, struct file *file,
uint cmd, ulong arg)
{
long val;
DPRINTK("smdk2410_audio_ioctl/n");
switch (cmd) {
case SNDCTL_DSP_SETFMT:
get_user(val, (long *) arg);
if (val & AUDIO_FMT_MASK) {
audio_fmt = val;
break;
} else
return -EINVAL;
case SNDCTL_DSP_CHANNELS:
case SNDCTL_DSP_STEREO:
get_user(val, (long *) arg);
if (cmd == SNDCTL_DSP_STEREO)
val = val ? 2 : 1;
if (val != 1 && val != 2)
return -EINVAL;
DPRINTK("audio_channels set to %d/n", val);
audio_channels = val;
break;
case SOUND_PCM_READ_CHANNELS:
DPRINTK("audio_channels is %d/n", audio_channels);
put_user(audio_channels, (long *) arg);
break;
case SNDCTL_DSP_SPEED:
get_user(val, (long *) arg);
val = audio_set_dsp_speed(val);
if (val < 0)
return -EINVAL;
put_user(val, (long *) arg);
break;
case SOUND_PCM_READ_RATE:
put_user(audio_rate, (long *) arg);
break;
case SNDCTL_DSP_GETFMTS:
put_user(AUDIO_FMT_MASK, (long *) arg);
break;
case SNDCTL_DSP_GETBLKSIZE:
if(file->f_mode & FMODE_WRITE)
return put_user(audio_fragsize, (long *) arg);
else
return put_user(audio_fragsize, (int *) arg);
case SNDCTL_DSP_SETFRAGMENT:
if (file->f_mode & FMODE_WRITE) {
if (output_stream.buffers)
return -EBUSY;
get_user(val, (long *) arg);
audio_fragsize = 1 << (val & 0xFFFF);
if (audio_fragsize < 16)
audio_fragsize = 16;
if (audio_fragsize > 16384)
audio_fragsize = 16384;
audio_nbfrags = (val >> 16) & 0x7FFF;
if (audio_nbfrags < 2)
audio_nbfrags = 2;
if (audio_nbfrags * audio_fragsize > 128 * 1024)
audio_nbfrags = 128 * 1024 / audio_fragsize;
if (audio_setup_buf(&output_stream))
return -ENOMEM;
}
if (file->f_mode & FMODE_READ) {
if (input_stream.buffers)
return -EBUSY;
get_user(val, (int *) arg);
audio_fragsize = 1 << (val & 0xFFFF);
if (audio_fragsize < 16)
audio_fragsize = 16;
if (audio_fragsize > 16384)
audio_fragsize = 16384;
audio_nbfrags = (val >> 16) & 0x7FFF;
if (audio_nbfrags < 2)
audio_nbfrags = 2;
if (audio_nbfrags * audio_fragsize > 128 * 1024)
audio_nbfrags = 128 * 1024 / audio_fragsize;
if (audio_setup_buf(&input_stream))
return -ENOMEM;
}
break;
case SNDCTL_DSP_SYNC:
return audio_sync(file);
case SNDCTL_DSP_GETOSPACE:
{
audio_stream_t *s = &output_stream;
audio_buf_info *inf = (audio_buf_info *) arg;
int err = access_ok(VERIFY_WRITE, inf, sizeof(*inf));
int i;
int frags = 0, bytes = 0;
if (err)
return err;
for (i = 0; i < s->nbfrags; i++) {
if (s->buffers[i].sem.count > 0) {
if (s->buffers[i].size == 0) frags++;
bytes += s->fragsize - s->buffers[i].size;
}
}
put_user(frags, &inf->fragments);
put_user(s->nbfrags, &inf->fragstotal);
put_user(s->fragsize, &inf->fragsize);
put_user(bytes, &inf->bytes);
break;
}
case SNDCTL_DSP_GETISPACE:
{
audio_stream_t *s = &input_stream;
audio_buf_info *inf = (audio_buf_info *) arg;
int err = access_ok(VERIFY_WRITE, inf, sizeof(*inf));
int i;
int frags = 0, bytes = 0;
if (!(file->f_mode & FMODE_READ))
return -EINVAL;
if (err)
return err;
for(i = 0; i < s->nbfrags; i++){
if (s->buffers[i].sem.count > 0)
{
if (s->buffers[i].size == s->fragsize)
frags++;
bytes += s->buffers[i].size;
}
}
put_user(frags, &inf->fragments);
put_user(s->nbfrags, &inf->fragstotal);
put_user(s->fragsize, &inf->fragsize);
put_user(bytes, &inf->bytes);
break;
}
case SNDCTL_DSP_RESET:
if (file->f_mode & FMODE_READ) {
audio_clear_buf(&input_stream);
}
if (file->f_mode & FMODE_WRITE) {
audio_clear_buf(&output_stream);
}
return 0;
case SNDCTL_DSP_NONBLOCK:
file->f_flags |= O_NONBLOCK;
return 0;
case SNDCTL_DSP_POST:
case SNDCTL_DSP_SUBDIVIDE:
case SNDCTL_DSP_GETCAPS:
case SNDCTL_DSP_GETTRIGGER:
case SNDCTL_DSP_SETTRIGGER:
case SNDCTL_DSP_GETIPTR:
case SNDCTL_DSP_GETOPTR:
case SNDCTL_DSP_MAPINBUF:
case SNDCTL_DSP_MAPOUTBUF:
case SNDCTL_DSP_SETSYNCRO:
case SNDCTL_DSP_SETDUPLEX:
return -ENOSYS;
default:
return smdk2410_mixer_ioctl(inode, file, cmd, arg);
}
return 0;
}
open：
判断设备是否正忙->设置相关参数->初始化iis总线->清除缓冲区
static int smdk2410_audio_open(struct inode *inode, struct file *file)
{
int cold = !audio_active;
DPRINTK("audio_open/n");
if ((file->f_flags & O_ACCMODE) == O_RDONLY) {
if (audio_rd_refcount || audio_wr_refcount)
return -EBUSY;
audio_rd_refcount++;
} else if ((file->f_flags & O_ACCMODE) == O_WRONLY) {
if (audio_wr_refcount)
return -EBUSY;
audio_wr_refcount++;
} else if ((file->f_flags & O_ACCMODE) == O_RDWR) {
if (audio_rd_refcount || audio_wr_refcount)
return -EBUSY;
audio_rd_refcount++;
audio_wr_refcount++;
} else
return -EINVAL;
if (cold) {
audio_rate = AUDIO_RATE_DEFAULT;
audio_channels = AUDIO_CHANNELS_DEFAULT;
audio_fragsize = AUDIO_FRAGSIZE_DEFAULT;
audio_nbfrags = AUDIO_NBFRAGS_DEFAULT;
if ((file->f_mode & FMODE_WRITE)){
init_s3c2410_iis_bus_tx();//可写则初始化iis发送
audio_clear_buf(&output_stream);
}
if ((file->f_mode & FMODE_READ)){
init_s3c2410_iis_bus_rx();//可读则初始化iis接收
audio_clear_buf(&input_stream);
}
}
return 0;
}
release：
清除缓冲区，读写计数归0
static int smdk2410_audio_release(struct inode *inode, struct file *file)
{
DPRINTK("audio_release/n");
if (file->f_mode & FMODE_READ) {
if (audio_rd_refcount == 1)
audio_clear_buf(&input_stream);
audio_rd_refcount = 0;
}
if(file->f_mode & FMODE_WRITE) {
if (audio_wr_refcount == 1) {
audio_sync(file);
audio_clear_buf(&output_stream);
audio_wr_refcount = 0;
}
}
return 0;
}
mixer驱动：
fops结构体
static struct file_operations smdk2410_mixer_fops = {
ioctl: smdk2410_mixer_ioctl,
open: smdk2410_mixer_open,
release: smdk2410_mixer_release
};
ioctl：同样根据oos audio programe guide完成相应功能，通过audio的ioctl调用
static int smdk2410_mixer_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
int ret;
long val = 0;
DPRINTK("smdk2410_mixer_ioctl/n");
switch (cmd) {
case SOUND_MIXER_INFO:
{
mixer_info info;
strncpy(info.id, "UDA1341", sizeof(info.id));
strncpy(info.name,"Philips UDA1341", sizeof(info.name));
info.modify_counter = audio_mix_modcnt;
return copy_to_user((void *)arg, &info, sizeof(info));
}
case SOUND_OLD_MIXER_INFO:
{
_old_mixer_info info;
strncpy(info.id, "UDA1341", sizeof(info.id));
strncpy(info.name,"Philips UDA1341", sizeof(info.name));
return copy_to_user((void *)arg, &info, sizeof(info));
}
case SOUND_MIXER_READ_STEREODEVS:
return put_user(0, (long *) arg);
case SOUND_MIXER_READ_CAPS:
val = SOUND_CAP_EXCL_INPUT;
return put_user(val, (long *) arg);
case SOUND_MIXER_WRITE_VOLUME:
ret = get_user(val, (long *) arg);
if (ret)
return ret;
uda1341_volume = 63 - (((val & 0xff) + 1) * 63) / 100;
uda1341_l3_address(UDA1341_REG_DATA0);
uda1341_l3_data(uda1341_volume);
break;
case SOUND_MIXER_READ_VOLUME:
val = ((63 - uda1341_volume) * 100) / 63;
val |= val << 8;
return put_user(val, (long *) arg);
case SOUND_MIXER_READ_IGAIN:
val = ((31- mixer_igain) * 100) / 31;
return put_user(val, (int *) arg);
case SOUND_MIXER_WRITE_IGAIN:
ret = get_user(val, (int *) arg);
if (ret)
return ret;
mixer_igain = 31 - (val * 31 / 100);
/* use mixer gain channel 1*/
uda1341_l3_address(UDA1341_REG_DATA0);
uda1341_l3_data(EXTADDR(EXT0));
uda1341_l3_data(EXTDATA(EXT0_CH1_GAIN(mixer_igain)));
break;
default:
DPRINTK("mixer ioctl %u unknown/n", cmd);
return -ENOSYS;
}
open，release：
空函数，略
以上ioctl参考资料：
http://manuals.opensound.com/developer/ioctl.html
2，dma分析
(1)两个相关结构体：
buffer结构:
typedef struct {
int size; /* buffer size */
char *start; /* point to actual buffer */
dma_addr_t dma_addr; /* physical buffer address */
struct semaphore sem; /* down before touching the buffer */
wait_queue_head_t wait;
int master; /* owner for buffer allocation, contain size when true */
} audio_buf_t;
内存块结构：
typedef struct {
audio_buf_t *buffers; /* pointer to audio buffer structures */
audio_buf_t *buf; /* current buffer used by read/write */
u_int buf_idx; /* index for the pointer above */
u_int fragsize; /* fragment i.e. buffer size */
u_int nbfrags; /* nbr of fragments */
dmach_t dma_ch; /* DMA channel (channel2 for audio) */
u_int dma_ok;
} audio_stream_t;
(2)dma使用过程：
首先是在probe函数中调用audio_init_dma初始化dma：
static int __init audio_init_dma(audio_stream_t * s, char *desc)
{
int ret ;
enum s3c2410_dmasrc source;
int hwcfg;
unsigned long devaddr;
int dcon;
unsigned int flags = 0;
DPRINTK("audio_init_dma/n");
if(s->dma_ch == DMA_CH2){//dma通道2初始化
source = S3C2410_DMASRC_MEM;
hwcfg = 3;
devaddr = 0x55000010;
dcon = (1<<31) | (0<<30) | (0<<24);
flags = S3C2410_DMAF_AUTOSTART;
ret = s3c2410_dma_request(s->dma_ch, &s3c2410iis_dma_out, NULL);//为out申请dma通道
if (!ret & DMACH_LOW_LEVEL) {
printk(KERN_ERR "failed to get dma channel/n");
return ret;
}
//4个dma相关设置：device设置，传输设置，回调函数设置，标志设置
s3c2410_dma_devconfig(s->dma_ch, source, hwcfg, devaddr);
s3c2410_dma_config(s->dma_ch, 2, dcon);
s3c2410_dma_set_buffdone_fn(s->dma_ch, audio_dmaout_done_callback);
s3c2410_dma_setflags(s->dma_ch, flags);
s->dma_ok = 1;
return ret;
}
else if(s->dma_ch == DMA_CH1){
source =S3C2410_DMASRC_HW;
hwcfg =3;
devaddr = 0x55000010;
dcon = (1<<31) | (1<<23) | (2<<24);
flags = S3C2410_DMAF_AUTOSTART;
ret = s3c2410_dma_request(s->dma_ch, &s3c2410iis_dma_in, NULL);//为in申请dma通道
if (!ret & DMACH_LOW_LEVEL) {
printk(KERN_ERR "failed to get dma channel/n");
return ret;
}
//同上，4个dma相关设置：device设置，传输设置，回调函数设置，标志设置
s3c2410_dma_devconfig(s->dma_ch, source, hwcfg, devaddr);
s3c2410_dma_config(s->dma_ch, 2, dcon);
s3c2410_dma_set_buffdone_fn(s->dma_ch, audio_dmain_done_callback);
s3c2410_dma_setflags(s->dma_ch, flags);
s->dma_ok =1;
return ret ;
}
else
return 1;
}
接着在读写函数中调用建audio_setup_buf立dma内存空间（读为in通道建立，写为out通道建立）：
static int audio_setup_buf(audio_stream_t * s)
{
int frag;
int dmasize = 0;
char *dmabuf = 0;
dma_addr_t dmaphys = 0;
DPRINTK("audio_setup_buf/n");
if (s->buffers)
return -EBUSY;
s->nbfrags = audio_nbfrags;
s->fragsize = audio_fragsize;
s->buffers = (audio_buf_t *)
kmalloc(sizeof(audio_buf_t) * s->nbfrags, GFP_KERNEL);//动态获得内存块空间
if (!s->buffers)
goto err;
memset(s->buffers, 0, sizeof(audio_buf_t) * s->nbfrags);
for (frag = 0; frag < s->nbfrags; frag++) {//为内存块每个buffer建立dma映射
audio_buf_t *b = &s->buffers[frag];
if (!dmasize) {
dmasize = (s-<
{var%20f='http://v.t.sina.com.cn/share/share.php?appkey=1515056452',u=z||d.location,p=['&url=',e(u),'&title=',e(t||d.title),'&source=',e(r),'&sourceUrl=',e(l),'&content=',c||'gb2312','&pic=',e(p||'')].join('');function%20a(){if(!window.open([f,p].join(''),'mb',['toolbar=0,status=0,resizable=1,width=440,height=430,left=',(s.width-440)/2,',top=',(s.height-430)/2].join('')))u.href=[f,p].join('');};if(/Firefox/.test(navigator.userAgent))setTimeout(a,0);else%20a();})(screen,document,encodeURIComponent,'','','https://www.xiaopingtou.cn//data/attach/topic/topicKPo7gB.jpg', '推荐 光伏电子 的文章《s3c2440 uda1341声卡驱动分析(目前完全看不懂，努力努力再努力中)》','https://www.xiaopingtou.net/article-84682.html','页面编码gb2312|utf-8默认gb2312'));){kind=link}