davinci之路CMEM模块分析

1、DAVINCIZ路一CMEM模块分析 HYPERLINK mailto:cmem用丁管理一个或者多个连续的物理块内存并提供地址转换（虚拟地址转换到物理地址或物理地址转换到虚拟地址）功能，物理连续地址内存用丁主处理器与DSP（或者协处理器、DMA）的数据BUF共享。在系统启动的时候，av_captui*e_loadsh运彳亍加载cmenikko驱动初始化，注册字符设备CMEM,并传递命令参数到内核，格式如下：Insmodcmemk.kophys_start=0 x83C00000,phys_end=0 x88000000pools=50 x512,2x4096,2x8192,2x16384,1x

2、3276&lx51200,1x102400,1x4096000phys_start、phys_end代表ChlEM的开始和结束物理地址，16进制表示。pools代表分配的内存池，指定了人小和数気如50 x512,表示分配50个512人小的空间，十进制表示。上面SH文件中的命令行创建了8个pools分别是:50buffeisofsize512,2buffeisofsize40962buffetsofsize8192,2buffersofsize16384,1buffersofsize32768,1buffersofsize51200,1buffetsofsize102400,1buffersof

3、size4096000。实际分配是以页为最小单位，人小依赖于平台页的犬小（PAGE_SIZE,一般为4K）,如50 x512,实际分配的是50 x4096。因此实际分配的Pools空间人丁等丁命令行请求的人小。CMEM剩余空间用T-Heap的分配。Davinci系统内存可以分成两人类：LINUX系统管理kmalloc获取内核空间内存，malloc获取用户空间内存。CMEM模块管理CMEMalloc获得cmem内存，CMEM_free（）释放cmem内存图一通过修改U-BOOT的参数bootargs配置丄inux系统内存人小，剩卜-的内存通过加载;CMEM,用于内核模块CMEM使用。CMEM内存

4、可以分成4种类型：Video/AudiocodecusagememoiyEncodedatacircularbufferCachepoolbufferInput/outputbufferCMEM模块软件结构包括两部分：驱动和封装的中间库。中间库是调用驱动的接II(open、release、mmap、ioctl)实现，用于向应用层提供统一API接11函数。提供的API接II如F：/*InitializetheCMEMmodule.MustbecalledbeforeotherAPIcalls.7intCMEMjnit(void)/FinalizetlieCMEMmodule.7CMEM_exit

5、(void)/*FindthepoolthatbestfitsagivenbuffersizeandhasabufferavailableintCMEM_getPool(sizeJsize)/*Allocatememoiyfi-omaspecifiedpool*/void*CMEMallocPool(intpoolid.CMEM_AllocParamsparams)/*Allocatememoryofaspecifiedsize.*/void*CMEMalloc(sizejsize,CMEM_AlhcParamsparams)/*Freeabufferpreviouslyallocatedwi

6、tliCMEM_alloc()/CMEM_allocPool0.*/intCMEMjis(voidptr.CMEM_Al.locParamsparams)/*Registersharedusageofanalready-allocatedbuffer.*/void*CMEM迄gist岔Alloc(unsignedbngphysp)/*UnregisteruseofabufferpreviouslyregisteredwithCMEMj-egisterAllocO*/intagister(void水ph：CMEM_AllocParamsparams)/*Getthephysicaladdress

7、ofacontiguousbuffer/unsignedlongCMEMPhys(voidptr)以H264编码算法为例，算法内存分配主要用到以下5个API接口函数：CMEMjnit,CMEM_exit,CMEM_alloc,CMEM_free,CMEMgetPhySo1、CMEMmtO源代码：intCMEM_imt(void)intflags;unsignedintversion,广调用了CMEM驱动接口open,open中的具体实现将在CMEM驱动中说I卅/cmem_fd=openC/dev/cmem-,O_RDWR),if(cmem_fd=-1)_E(-imtFailedtoopen/d

8、ev/cniem:%s*nstreiror(ernw),return1,ref_count+;/*版本检査*/version=CMEM_getVersionOif(version&OxffifDOOO)!=(CMEM_VERSION&0 x任ffOOOO)_E(-imt:majorversionmismatchbetweeninterfaceanddrivern)t_E(Bneedsdiiverversion%#x,got%#xnu,CMEM_VERSION,version);CMEM_exitO；return1,)elseif(version&OxOOOOffif)type=CMEM_POO

9、L)returngetAndAllocFromPool(blockid,size,params)/分配Pool空间elsereturnallocFromHeap(blockidsize,params”/分配He却空间)2.1、getAndAllocFromPool()源代码：staticvoid*getAndAllocFromPool(intblockid,sizesize,CMEMAllocParains*parains)intpoolid,/*briefFindthepoolinmemoryblockblockidthatbestfitsagivenbuffersizeandhasabuf

10、feravailable*/.poolid=CMEM_getPool2(blockid,size),if(poolid=-1)returnNULL;广根据poolid,获得pool空间拿/returnallocFromPool(blockid,poolid,params);2.2、allocFromHeap()源代码:staticvoid*allocFromHeap(intblockid,size_tsize,CMEM_AllocParains*parains)void*usei-p,unionCMEM_A11ocUnionallocDesc;unsignedlongphysp,unsigne

11、dintcmd,intrv,cmd=CMEM_IOCALLOCHEAP|parains-flags,allocDesc.alloc_heap_mparams.size=size,allocDesc.alloc_heapjnparains.align=params-alignment=0?1parainsalignment,allocDesc.alloc_heapjnparains.blockid=blockid;rv=ioctl(cmeni_fd,cmd,&allocDesc);if(rv!=0)(_E(-allocHeap:loctl%sfailed:%dncmd=CMEMJOCALLOCH

12、EAP?MEMJOCALLOCHEAPMCMEMJOCALLOCHEAPCACHEDrv);returnNULL,)physp=allocDesc.physp,_D(allocHeapallocatedphysbuffer%xn,physp);/*Mapthephysicaladdresstouserspace*/userp=mmap(0,/Preferredstartaddresssize,/LengthtobemappedPROT_WRITE|PROT_READ,/ReadandwriteaccessMAP_SHARED,/Sharedmemorycmem_fd,/Filedescnpto

13、rphysp);/Thebyteoffsetfromfdif(userp=MAPFAILED)_ECallocHeap:Failedtonimapbufferatphysicaladdress%Sxnu,physp);_E(BFreeingphysbufferphysp);ioctl(cmem_fd,CMEMOCFREEHEAPPHYS,问hysp),returnNULL,_D(allocHeapmmapsucceeded,returningvirtbuffer%pn,userp);returnuserp;上山j的廉API都是基丁驱动CMEM捉供的接口(open、release、mmap、io

14、ctl)实现，以下分析CMEM驱动的各个接口的具体实现。在SH文件av_capture_load.sh运行加载cmemk.ko时，驱动中初始化函数anemjmt()执彳亍。主耍完全字符设备CMEM的注册，根据cmemk.ko传递的参数完成POOLS.Heap的初始化。字符设备提供的文件操作结构描述定义如2staticstructfile_operationscmemfens=ioctl:ioctl,mmap:mmap,open:open,release:release；1、open接LIstaticintopen(structinode*inode,structfile*filp)atomic

15、_inc(&refeience_count),/*原子变t的初始化水/retuiTi0t2、mmap接I丨staticintmmap(structfile水flip,structvm_area_struct*vma)tuisignedlongphysp,structpool_buffer水entry,physp=vma-vm_pgoffPA.GE_SHIFT,if(down_mterruptible(&cmem_mutex)return-ERESTARTSYS,/*looksforanallocatedpoolbufferwithphyisicaladdrphysp*/entiy=find_b

16、usy_entiy(physp,NULL,NULL,NULL),up(&cmem_mutex)if(entry!=NULL)if(entiy-flags&CMEM_CACHED)_DCmmap:callingset_cached(%p)An11,vma),returnset_cached(vma)”else_DCmmap:callingset_noncached(%p).An1,vma),returnset_noncached(vma)”else_Cmmap:cantfindallocatedbufferwithphysp%lxnB,physp),return-EINVAL,3xioctl接【

17、IIoctl支持的命令有CMEM_IOCALLOC、CNIEMJOCALLOCHEAPCMEMJOCFREE.CMEMJOCGETPHYS.CMEM_IOCGETSIZE、CMEMJOCGETPOOLCMEMJOCCACHE.CMEM_IOCGETVERSION、CMEMJOCGETBLOCK.CMEMJOCREGUSER以DM365的H264编码为例，主要用到的IOCTL命令有：CMEMJOCALLOCHEAP,CMEMJOCFREE.CMEM_IOCGETPHYS、CMEM_IOCC血CHE、CN1EM_IOCGETVERSION下面的兀码也仅以使用的IOCTL做为简单说明。一一stati

18、cmtioctl(stnictmode愉ode,structfileunsignedmtcmd,unsignedlongais)unsignedmt_userzlzargp=(unsignedmt_user:l7args;stnicthstjieadzhzfreelistp=NULL;stnicthstjiead本biisylistp=NULL;stnicthstjiead:i：registeredhstp;stnicthstjiead:l:e=NULL;stnicthstjiead%;stnicthstjieadziimext;structpool_biifferzlentiy;struct

19、regisietdjiseriiser;unsignedlongpkysp;unsignedlongviitp,vutp_end;seeJ:reqsce,size,align;intdelta=MAXTYPE(mt);mtpool=-1I,bi,id;structblockjtnictblock;imionCMEM_AllocUnionallocDesc;switch(emd&CMEMJOCCMDMASK)caseCMEMOCALLOCHEAP:/Heap的分配pnntkCCMEMJOCALLOCHEAPnu);if(copyJromjiser(&allocDesc,argp,sizeofia

20、llocDesc)return-EFAULT;size=allocDesc.allocJeapjnparams.size;align=allocDesc.allocJieapjnparams.align;bi=allocDesc.allocJieapjnparatns.blocked;_D(nALLOCHEAP%sloctlreceivedonheappoolforblock%dntf,cmd&CMEMJJACHED?“CACHED”:Ubi);页(bi=NBLOCKS)_E(nioctl:invalidblockid%d,mustbephysp=physp;entjy-kvutp=virtp

21、;entjy-ste=see;entiy-flags=emd&CMEMOCCMDMASK;INIT_LIST中EAD(&entiy-iisers);biisyhstp=&pj)bjsbiheapj?oolbiJ.biisydist;hst_ciddjail(&entiy-element,biisylistp);user=kmcdloc(s匸eqfistructlgisteiedjiser),GFP_KERNEL);tiser-filp=flip;list_cidd(&iiser-element,&entjy-iisers);tip(&cmemjmitex);tf(piitjiser(psp,a

22、jp)return-EFAULT;_D(nALLOCHEAP%s:allocated%#vsizebttfferat(physaddress)nft,and&CMEMCACHED?uCACHED19:tentjysize,entiy-physp);break;/:i：ajpcontainsapointertoanallocdescriptorcomingin,andthe*pricedaddiEssandsizeoftheallocatedbufferwhenreturning汨caseCMEMJOCALLOC:prmtkCCMEMJOCALLOCntf)；break;/:i：aipconta

23、inseithertheuservirtualaddressorthep呼sicaladdressofthebiiffertofreecomingm,andcontainsthepoolyvheieitwasfreedfromandthesizeoftheblockoni-etiirn.*1caseCMEMOCFREE:prmtkCCMEMJOCFREEnu);break;/:l:argpcontainstheuservirtualadd沱ssofthebicffertotranslatecomingin,andthetranslatedphysicaladd沱ssonreturn严/case

24、CMEMJOCGETPHYS:prmtk(ftGETPHYSloctlreceived.nu);页(getjiser(vutp,aip)return-EFAULT;physp=get_phys(virtp);if(P呼sp=(0L)_E(nGETPHYS:Failedtoconvertvirtual%#Zxtoph)sical.nu,viitp);return-EFAULT;tf(piitjiser(psp,argp)return-EFAULT;_D(”GETPHYS:itiUTiingphysp);break;/:l:argpcontainsthepooltoqueryforsizecoin

25、ingm,andthesize:l:ofthepooloni-etiirn.7caseCMEMJOCGETSIZE:prmtk(GETSIZEloctliceivedntf)；break;严argpcontainstheleqiiestedpoolbuffersizecomingin,andthe定poolid(index)on帧caseCMEMOCGETPOOL:根据请求的poolbufA小,返回poolidprmtk(uGETPOOLloctlleceived.nu);break;caseCMEMOCCACHE:prmtk(9tCACHE%s%sloctlieceived.nu,and&CMEMJVB?WB”:Ucmd&CMEMNV?:ttn)；if(copyjromjiser(&bloc匕argp,srzeof(block)return-EFAULT;vutp=block.addr;vutpynd=viitp+block.sne;switch(cmd)caseCMEMOCCACHEWB:VnfdefUSEJJACHEyOIDyiRGdmac_cleanjaange(voidzlz)vntp,(v