Linux音頻OSS的buffer分析

統(tǒng)一術(shù)語

1.??????JZ?????? ???????????????????????????????????? 君正4760b mips

2.??????Audio buff ?????????????????????????? 就是整個list_head+ list_node *4 + 整個音頻區(qū)

3.??????APP???????????????????????????????????????? 應(yīng)用程序

整體使用框圖

Buff分配流程

首先在probe JZ mixer設(shè)備的時候進行初始化DMA及緩沖buff. ?在函數(shù)init_jz_i2s中調(diào)用audio_init_endpoint進行實始化。

fragsize=?JZCODEC_RW_BUFFER_SIZE?*?PAGE_SIZE;??

fragstotal=?JZCODEC_RW_BUFFER_TOTAL;??

audio_init_endpoint(&out_endpoint,fragsize,?fragstotal);??

audio_init_endpoint(&in_endpoint,fragsize,?fragstotal);??

fragsize= JZCODEC_RW_BUFFER_SIZE * PAGE_SIZE;fragstotal= JZCODEC_RW_BUFFER_TOTAL;audio_init_endpoint(&out_endpoint,fragsize, fragstotal);audio_init_endpoint(&in_endpoint,fragsize, fragstotal);

進入audio_init_endpoint函數(shù)，在這里先表一下in_endpoint和out_ endpoint結(jié)構(gòu)體，?初始化為0.

static?audio_pipe?out_endpoint?=?{??

.mem?????????????????=?0,??

.savenode?????????=?0,??

.fragsize??=?0,??

.fragstotal????????=?0,??

.trans_state????=?0,??

};??

static?audio_pipe?in_endpoint=?{??

.mem?????????????????=?0,??

.savenode?????????=?0,??

.fragsize??=?0,??

.fragstotal????????=?0,??

.trans_state????=?0,??

};??

static audio_pipe out_endpoint = {.mem = 0,.savenode = 0,.fragsize = 0,.fragstotal = 0,.trans_state = 0,};static audio_pipe in_endpoint= {.mem = 0,.savenode = 0,.fragsize = 0,.fragstotal = 0,.trans_state = 0,};

void?audio_init_endpoint(audio_pipe*endpoint,?unsigned?int?pagesize,??

unsigned?int?count)??

{??

audio_resizemem_endpoint(endpoint,pagesize,?count);??

spin_lock_init(&endpoint->lock);??

init_waitqueue_head(&endpoint->q_full);??

endpoint->avialable_couter=?0;??

endpoint->filter=?NULL;??

if(endpoint?==?&in_endpoint)?{??

init_audio_audiodma(endpoint,CODEC_RMODE);??

//INIT_WORK(&endpoint->work,?audio_in_endpoint_work); ??

endpoint->handle=?handle_in_endpoint_work;??

}??

if(endpoint?==?&out_endpoint)?{??

init_audio_audiodma(endpoint,CODEC_WMODE);??

//INIT_WORK(&endpoint->work,?audio_out_endpoint_work); ??

endpoint->handle=?handle_out_endpoint_work;??

}??

}??

int?audio_resizemem_endpoint(audio_pipe*endpoint,?unsigned?int?pagesize,???

unsigned?int?count)??

{??

intret?=?init_audio_node(&endpoint->mem,?pagesize,?count,(int*)&endpoint->??

fragmem_start);??

if(ret)?{??

endpoint->fragsize=?pagesize;??

endpoint->fragstotal=?count;??

endpoint->memsize=?ret;??

}??

returnret;??

}??

void audio_init_endpoint(audio_pipe*endpoint, unsigned int pagesize,unsigned int count){audio_resizemem_endpoint(endpoint,pagesize, count);spin_lock_init(&endpoint->lock);init_waitqueue_head(&endpoint->q_full);endpoint->avialable_couter= 0;endpoint->filter= NULL;if(endpoint == &in_endpoint) {init_audio_audiodma(endpoint,CODEC_RMODE);//INIT_WORK(&endpoint->work, audio_in_endpoint_work);endpoint->handle= handle_in_endpoint_work;}if(endpoint == &out_endpoint) {init_audio_audiodma(endpoint,CODEC_WMODE);//INIT_WORK(&endpoint->work, audio_out_endpoint_work);endpoint->handle= handle_out_endpoint_work;}}int audio_resizemem_endpoint(audio_pipe*endpoint, unsigned int pagesize,unsigned int count){intret = init_audio_node(&endpoint->mem, pagesize, count,(int*)&endpoint->fragmem_start);if(ret) {endpoint->fragsize= pagesize;endpoint->fragstotal= count;endpoint->memsize= ret;}returnret;}

我們進入audio_resizemem_endpoint分析內(nèi)存的分配, 其中調(diào)用init_audio_node進行實質(zhì)的
分配， 先介紹一下這里的變量意義,了解了這些意義，分析起來就得心應(yīng)手了，迫不及待
了。

JZCODEC_RW_BUFFER_SIZE???????????//?1?*?4096 ??

JZCODEC_RW_BUFFER_TOTAL;??????//?4個buff ??

unsignedint?????fact;???????????????????//分配物理頁的order ??

audio_node??????*pbuff;???????????????//代表1個audio?node ??

audio_head??????*phead;?????????????//代表整個audiobuff?鏈表 ??

unsignedint?????*mem;??????????????//分配得到整個audiobuff的虛擬地址 ??

structlist_head?*audio_wfree;???????//freebuff?鏈表 ??

structlist_head?*audio_wuse;????????//usebuff?鏈表 ??

int????memsize;??????????????????????????????????????//鏈表頭+節(jié)點+audiobuff占用總空間 ??

int????datasize;?????????????????????????????//audiobuff占用的總空間 ??

int????headlistsize;???????????????????????//鏈表頭+4個節(jié)點占用總空間??

JZCODEC_RW_BUFFER_SIZE // 1 * 4096JZCODEC_RW_BUFFER_TOTAL; // 4個buffunsignedint fact; //分配物理頁的orderaudio_node *pbuff; //代表1個audio nodeaudio_head *phead; //代表整個audiobuff 鏈表unsignedint *mem; //分配得到整個audiobuff的虛擬地址structlist_head *audio_wfree; //freebuff 鏈表structlist_head *audio_wuse; //usebuff 鏈表int memsize; //鏈表頭+節(jié)點+audiobuff占用總空間int datasize; //audiobuff占用的總空間int headlistsize; //鏈表頭+4個節(jié)點占用總空間

//Alloc?memory?first,?to?avail?fail ??

datasize???=?ALIGN_PAGE_SIZE(pagesize?*?count);??

headlistsize??????=?ALIGN_PAGE_SIZE(count?*sizeof(audio_node)?+?sizeof(audio_head));??

memsize???????????=?headlistsize?+?datasize;??

fact???????????=?get_order(memsize);??

mem=?(unsigned?int?*)__get_free_pages(GFP_KERNEL?|?GFP_DMA,?fact);??

//Alloc memory first, to avail faildatasize = ALIGN_PAGE_SIZE(pagesize * count);headlistsize = ALIGN_PAGE_SIZE(count *sizeof(audio_node) + sizeof(audio_head));memsize = headlistsize + datasize;fact = get_order(memsize);mem= (unsigned int *)__get_free_pages(GFP_KERNEL | GFP_DMA, fact);

首先獲得整個audiobuff的大小 datasize, 再獲得list_head + list_node * 4的大小
headlistsize, 然后計算總大小memsize, 用__get_free_pages分配連續(xù)的物理地址空間，這里
注意一下，返回的是物理地址。

//Free?old?buffer ??

if(*memory)?{??

phead???????=?(audio_head?*)*memory;??

fact??=?phead->fact;??

free_pages((unsignedlong)*memory,?fact);??

*memory?=?NULL;??

}??

*memory=?mem;??

//Free old bufferif(*memory) {phead = (audio_head *)*memory;fact = phead->fact;free_pages((unsignedlong)*memory, fact);*memory = NULL;}*memory= mem;

這里檢查一下是不是有分配audiobuff, 如果有就釋放掉，再將新分配的地址賦值給memory.
在mixer的ioctl中SNDCTL_DSP_SETFRAGMENT也會重新分配大小的。

phead????????????????=?(audio_head?*)*memory;??

phead->fact?????=?fact;??

phead->listsize?????????=?headlistsize;??

phead->datasize??????=?datasize;??

audio_wuse?????=?&(phead->use);??

audio_wfree????=?&(phead->free);??

INIT_LIST_HEAD(audio_wuse);??

INIT_LIST_HEAD(audio_wfree);??

phead = (audio_head *)*memory;phead->fact = fact;phead->listsize = headlistsize;phead->datasize = datasize;audio_wuse = &(phead->use);audio_wfree = &(phead->free);INIT_LIST_HEAD(audio_wuse);INIT_LIST_HEAD(audio_wfree);

接下來就是給listhead賦值，然后初始化audio_wuse和audio_wfree鏈表。

pbuff=?(audio_node?*)((unsigned?int)*memory?+?sizeof(audio_head));??

*fragmem_start=?(int)((unsigned?int)*memory?+?headlistsize);??

for(i?=?0;?i?

pbuff->pBuf??????=?(unsigned?int)*memory?+?headlistsize?+pagesize?*?i;??

pbuff->phyaddr?????????=?(unsigned?int)virt_to_phys((void*)pbuff->pBuf);??

pbuff->start?????=?0;??

pbuff->end????????=?0;??

DEBUG??

pbuff->pBufID??=?i;??

DPRINT_Q("audio_notebuffer[%d]?=?%x\n",?i,?(unsigned?int)pbuff->pBuf);??

list_add(&pbuff->list,audio_wfree);??

pbuff++;??

}??

pbuff= (audio_node *)((unsigned int)*memory + sizeof(audio_head));*fragmem_start= (int)((unsigned int)*memory + headlistsize);for(i = 0; i < count; i++) {pbuff->pBuf = (unsigned int)*memory + headlistsize +pagesize * i;pbuff->phyaddr = (unsigned int)virt_to_phys((void*)pbuff->pBuf);pbuff->start = 0;pbuff->end = 0;#ifdef Q_DEBUGpbuff->pBufID = i;#endifDPRINT_Q("audio_notebuffer[%d] = %x\n", i, (unsigned int)pbuff->pBuf);list_add(&pbuff->list,audio_wfree);pbuff++;}

在這里將audio_wfree 鏈表全部初始化，注意此時wfree鏈表中有4個結(jié)點，wuse中

沒有結(jié)點。

if?(ret)?{??

endpoint->fragsize?=pagesize;??

endpoint->fragstotal?=count;??

endpoint->memsize?=?ret;??

}??

if (ret) {endpoint->fragsize =pagesize;endpoint->fragstotal =count;endpoint->memsize = ret;}

接下來返回到audio_resizemem_endpoint， 將endpoint結(jié)構(gòu)賦值。

Audio buff分配好后，再返回到audio_init_endpoint對DMA進行初始化， 這里根據(jù)傳
入的是play或者record進行初始化，大致上是雷同的，這里只分析 replay的初始化

if?((ch?=jz_request_aic_dma(DMA_ID_I2S_TX,"audio?dac",?jz_i2s_dma_irq,IRQF_DISABLED,???

endpoint))?

printk(KERN_ERR?"%s:can't?reqeust?DMA?DAC?channel.\n",?__FUNCTION__);??

return?-1;??

}??

chan->io???=?i;??

chan->dev_id???=?dev_id;??

chan->dev_str?=?dev_str;??

chan->fifo_addr????????=?CPHYSADDR(AIC_DR);??

switch?(dev_id)?{??

case?DMA_ID_AIC_TX:??

chan->mode?????=?DMA_AIC_TX_CMD_UNPACK?|?DMA_MODE_WRITE;??

chan->source???=?DMAC_DRSR_RS_AICOUT;??

break;??

case?DMA_ID_AIC_RX:??

chan->mode?????=?DMA_32BIT_RX_CMD?|?DMA_MODE_READ;??

chan->source???=?DMAC_DRSR_RS_AICIN;??

break;??

default:??

printk("JZ?AIC:?%s:%d,need?fix?!!!\n",?__FUNCTION__,?__LINE__);??

BUG_ON(1);??

}??

if ((ch =jz_request_aic_dma(DMA_ID_I2S_TX,"audio dac", jz_i2s_dma_irq,IRQF_DISABLED,endpoint)) < 0) {printk(KERN_ERR "%s:can't reqeust DMA DAC channel.\n", __FUNCTION__);return -1;}chan->io = i;chan->dev_id = dev_id;chan->dev_str = dev_str;chan->fifo_addr = CPHYSADDR(AIC_DR);switch (dev_id) {case DMA_ID_AIC_TX:chan->mode = DMA_AIC_TX_CMD_UNPACK | DMA_MODE_WRITE;chan->source = DMAC_DRSR_RS_AICOUT;break;case DMA_ID_AIC_RX:chan->mode = DMA_32BIT_RX_CMD | DMA_MODE_READ;chan->source = DMAC_DRSR_RS_AICIN;break;default:printk("JZ AIC: %s:%d,need fix !!!\n", __FUNCTION__, __LINE__);BUG_ON(1);}

調(diào)用jz_request_aic_dma函數(shù)注冊DMA中斷，填寫chan的模式與地址填充，最后啟動
AIC DMA的時鐘，再返回到init_audio_replaydma中，初始化寄存器，DMA就初始化OK了。
至此整個AUDIO BUFF就初始化完成了。

播放流程分析

先上圖來說話:

首先進入jz_audio_write函數(shù)， 里邊有兩個分支，根據(jù)模式進行區(qū)分的，第1種是使用
mmap方式傳輸?shù)?，由于我們要分析audio buff, 就不關(guān)注mmap方式了，各位如有想了解
的話，可以發(fā)與我討論, dyronchina@gmail.com, 下邊就直接進入audiobuff 方式的
jz_audio_write_data函數(shù)分析。

while(count?>=?pout_endpoint->fragsize)?{??

bat_cnt=?endpoint_put_userdata(pout_endpoint,??

&(buffer[usecount]),??

pout_endpoint->fragsize);??

//Prepare?data?success. ??

if(bat_cnt?>?0)?{??

usecount+=?bat_cnt;??

count-=?bat_cnt;??

DPRINT("bat_cnt=?%d\n",?bat_cnt);??

}??

//Perhaps?non?node?is?avialable. ??

elseif?(bat_cnt?==?0)?{??

DPRINT("bat_cnt==?0\n");??

break;??

}??

//Error?occured. ??

else{??

//break?and?handle?prepared?data. ??

if(usecount?>?0)?{??

DPRINT("bat_cnt?0\n");??

break;??

}??

//Has?not?prepared?any?data?and?return?error?when?prepared?data. ??

else{??

DPRINT("bat_cnt

returnbat_cnt;??

}??

}??

}??

while(count >= pout_endpoint->fragsize) {bat_cnt= endpoint_put_userdata(pout_endpoint,&(buffer[usecount]),pout_endpoint->fragsize);//Prepare data success.if(bat_cnt > 0) {usecount+= bat_cnt;count-= bat_cnt;DPRINT("bat_cnt= %d\n", bat_cnt);}//Perhaps non node is avialable.elseif (bat_cnt == 0) {DPRINT("bat_cnt== 0\n");break;}//Error occured.else{//break and handle prepared data.if(usecount > 0) {DPRINT("bat_cnt< 0, usecount > 0\n");break;}//Has not prepared any data and return error when prepared data.else{DPRINT("bat_cnt< 0, usecount == 0\n");returnbat_cnt;}}}

首先檢查傳入音頻塊的大小，必須大于fragsize(4096)，先來整體分析這個函數(shù)，然后
再進入內(nèi)部分析細節(jié)，bat_cnt 根據(jù)返回值進行處理，返回0表明沒有wfree節(jié)點，就直接
跳出，進行播放錄音了。

DPRINT("<<<);??

node=?endpoint_get_outnode(endpoint);??

if(!node)??

return0;??

if(copy_from_user((void?*)node->pBuf,?buffer,?count))?{??

printk("JZI2S:?copy_from_user?failed?!\n");??

return-EFAULT;??

}??

LEAVE();??

returnendpoint_post_outnode(endpoint,node,count);??

DPRINT("<<

用endpoint_get_outnode獲得一個wfreenode，獲得一個后就從wfree list上刪除掉當(dāng)

前節(jié)點， 播放完成后就返回結(jié)點，這樣就形成了一個環(huán)形緩沖區(qū)。

最后返回到j(luò)z_audio_write_data， 最后如果當(dāng)前while 循環(huán)結(jié)束后還有剩余的數(shù)據(jù)，就
重新做一次播放。

錄音流程分析??????????????

由于播放和錄音基本上是雷同的，故在此不做分析了

?