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
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