Linux-PCI Support Programming PCI-Devices …

1 Intendedtobea ..PCI-BridgePCI-BusPCI#0 PCI#nPCI#1 Figure1:TheArchitectureofthePCIS ubsystemThePeripheralComponentInterconne ct-Bus(PCI)todayis presentina widevarietyof thecom-pleteseparationof , specialcasesonlyonestartad-dressis transferredfollowedbya determinetheaddressforeachsingledata-wor dthePCI-BridgeandthePCI-Adapterincrement internalcounters, burst cy-clespeedsupthetransfersigni cantly(upto266 Mbyte/secfora 64bitdata-transfer).Thankstotheintellige nthandlingof schematicviewof thePCIsubsystemis usea Memoryforcon beplacedin therightplaces,soIRQor addresscon ictsarenolongera commonlyknownasPlug& ( ) linux -PCIS upportFirstContactwiththePCIsubsystemTo getanimpressionhowlinuxseesthePCIbusinyo urcomputertrygettingthePCIbuscon gurationfromthekernelwithcat /proc/pci.

2 If everythingworksOKyouwill(hopefully)see:P CI devicesfound:Bus0, device12, function0:SCSI storagecontroller:AdaptecAIC-7881U(rev0) . Gnt= at bit memoryat , device11, function0:VGA compatiblecontroller:S3 (rev0). bit memoryat , device10, function0:Ethernetcontroller:3 Com3C59010bT(rev0). Gnt= at , device7, function2:Unknownclass:IntelUnknowndevic e(rev0).Vendorid= 9. at , device7, function1:IDE interface:Intel82371 SBTritonII PIIX(rev0). at , device7, function0:ISA bridge:Intel82371 SBTritonII PIIX(rev0). , device0, function0:Hostbridge:Intel82439 HXTritonII (rev1). Eachdevicecon- gurationblockis assignedto a deviceanda identifya certaindevicewhiledriverwritingyouwillat leasthaveto knowthevendor- andthedevice-idthatis staticallystoredinthedevicecon gura-tionblock(asdiscussedlateron).

3 'sordeviceclass eldsthatcannotberesolvedwithinthelinuxPC I-subsystemareprintedasplainvalues,sodri verwritershavea simplechancetoidentifytheircardofchoicew ithoutwrit-inga specialtoolto gurationBlockAsmentionedaboveeachPCI-dev icehasitsownassigned256bytesPCI-con gurationmemoryblockthatis rst64bytesofthisreservedspaceareusedto identifyandcon gura-tionblockarereplacedfromthePlug&Pla yBIOS thatcon g-urationblocksofthePCIsubsystemcanbeacc essedthroughtheCONFIGADDRESSTheLinuxLabP rojectwhitepapers11/1996( ) linux -PCIS upport(0xcf8)andtheCONFIGDATA(0xcfc)regi stersTheLinuxPCI-biossupportisimple-ment edontopof theBios32routinesandde nessomeusefulroutinesto handlethePCIcon gurationblockandcon runonmanyhardwarearchitec-turesit is recommendedtousethisfunc-tionsinsteadofa ccessingthecon PCI-boardcanbeused,thedriverhasto determinetheboardspeci cparam-etersfromthecon donebyaautodetectroutinein thekerneldriverthatperformsthefollowingt asks.

4 Checkif thePCI-BiosSupportis en-abledinthekernelandtheBIOS ispresentwithpcibiospresent() Getthecon gurationblockforthedesireddeviceusingpci biosfinddevice() Getthedesiredparametersfromthecon gurationblockus-ingpcibiosreadconfigbyte (),pcibiosreadconfigword()orpcibiosreadc onfigdword()toget8,16or32bitparameterval ues. Setthedesiredparametersinthecon gurationblockusingpcibioswriteconfigbyte (),pcibioswriteconfigword()orpcibioswrit econfigdword()Thefollowingexamplefromthe ne2000clonedrivershowshowthistaskisper-f ormedin a realkernelnetworkdriver.#if defined(CONFIG_PCI)if (pcibios_present()){int pci_index;for (pci_index= 0; pci_index< 8; pci_index++){unsignedcharpci_bus,pci_dev ice_fn;unsignedint pci_ioaddr;/* CurrentlyonlyRealtekare makingPCI ne2kclones.}}

5 */if (pcibios_find_device(PCI_VENDOR_ID_REALT EK,PCI_DEVICE_ID_REALTEK_8029,pci_index, &pci_bus,&pci_device_fn)!= 0)break;/* OK, now try to probefor card*/pcibios_read_config_byte(pci_bus,p ci_device_fn,PCI_INTERRUPT_LINE,&pci_irq _line);pcibios_read_config_dword(pci_bus ,pci_device_fn,PCI_BASE_ADDRESS_0,&pci_i oaddr);/* Stripthe I/O addressout of the returnedvalue*/pci_ioaddr&= PCI_BASE_ADDRESS_IO_MASK;/* Avoidalreadyfoundcardsfrompreviousne_pro be()calls*/if (check_region(pci_ioaddr,NE_IO_EXTENT))c ontinue;printk(" :PCI BIOS reportsne2000cloneat i/o %#x,irq %d.\n",pci_ioaddr,pci_irq_line);if (ne_probe1(dev,pci_ioaddr)!= 0) {/* Shouldn'thappen.*/printk(KERN_ERR" :Probeof PCI cardat %#x failed.)}

6 \n",pci_ioaddr);break;/* Hrmm,try to probefor ISA */}TheLinuxLabProjectwhitepapers11/1996( ) linux -PCIS upportpci_irq_line= 0;return0;}}#endif/* defined(CONFIG_PCI)*/ThiscardusesoneIRQa ndonebasead-dressinI/Ospacetocommunicate withthedriver. Thelowerbitsofthereturnedbaseaddresshave differentmeaningsde-pendingif theaddressisanI/Oaddressora memorymappedareais isalways1 andbit2 memorymappedaddresstypethelower4 bitshavethefol-lowingmeanings:BitDescrip tion0alwayszero1-2adresstype:00=arbitrar y32bit,01=below1M,10=arbitrary64-bit3pre fetchableTo keepthingssimpleLinuxde thePCI-bridgeisallowedtoreadthememoryblo ckina prefetchbufferwith-outproblems,thisis normallythecaseifthememoryblockis a memoryareaonthePCI-device,if wholebunchofothersetableandreadableparam etersinthecon gura-tionblock,thatcanbeaccessedthrought helinuxpcibiosXXX()

7 NessomeusefulMnemonicstogainsimpleaccess tothecon gurationblockparametervaluesthatarede nedininclude/ ,2and3 willdescribetheMacrosin deviceReadingandwritingtoa PCIdeviceis aseasyasreadingandwritingto anISAboardorreadingandwritingtoa memoryareadependingonthebaseaddresstypeo f thedeviceusesanI/Otypebasead-dress,norma lI/Ocanbeperformedusingtheusualinb()/out b(),inw()/outw()orthe32bitinl()/outl() ()/writeb(),readw()/writew()orthelongwor dreadl()/writel()rou-tinestoreadorwritet oa singlelocation(seeinclude/ ).memcpy()canalsobeusedtotransfera (onefortheBusside,onefortheCPUsubsystems ide)thatareusedto storetransferdatabeforea sendor receiveis thePREF(prefetchable)bitis setin thebaseaddressbit3, thememoryareaisnonprefetchable, intendedfordevicesthatmapsspecialregiste rsinamemoryareasotheCPUcanreadorwritethi sregisterswithouta controllercantransferitsdatatothememoryw ith-outanyCPUactionbydrivingtheap-propri atebus-linesona ( ) busmastertransferhasbeenabortedbythebusm asterdevice,thePCISTATUSRECMASTERABORT bitinthePCISTATUS registeris set,onthereceivingendanabortcanbenoti ( ) ThisIDis de nedbythePCIconsortiumPCIDEVICEID16bitUni queDeviceID( )

8 Thisis de nedbythevendoruniqueforeachdevicePCICOMM AND16bitThis eldisusedfordevicespeci ccon gurationcommands(seetable2)PCISTATUS16bi tThisis usedforboardspeci cstatusresults(seetable3)PCICLASSREVISIO N32bitThehigh24bitsareusedtodeterminethe device'sclasstypethelow8bitforrevisionco dePCICLASSDEVICET hedevice'sclasscode( )PCIBIST8bitIfPCIBISTCAPABLEis setthedevicecanperforma Build-inselftestthatcanbestartedbywritin gPCIBISTSTART tothis estheLayouttypeforthefollowing48bytesin PCIcon guration(currentlyonly0x0)PCILATENCYTIME R8bitThisis themaximaltimea PCIcyclemayconsume(time=latency+8cycles) PCICACHELINESIZE8bitSpeci estheCache-LineSizeinunitsof 32bytes,PCIBASEADDRESS[0-5]32bitThisareu pto6 memorylocationsthedevicecanmapitsmemorya rea(s) bitsareusedto specifythetypeandtheaccessmodeof thestartaddressofthedevice'sROMarea.

9 (writebit1 to enableROM)PCIMINGNT8bitminimallatencytim e(vendorspeci c)PCIMINLAT8bitmaximallatencytime(vendor speci c)PCIINTERRUPTPIN8bitThisentrydenotesthe IRQpinthatshouldbeused1=INTA2=INTB0=disa bledPCIINTERRUPTLINE8bitThisentryspeci estheinterruptlineonwhichthedeviceIRQis mapped(usuallyIRQ0-15)Table1:TheLinuxPCI -Con gurationmacrosTheLinuxLabProjectwhitepap ers11/1996( ) linux -PCIS upportMacroDescriptionPCICOMMANDIOE nableI/OareaPCICOMMANDMEMORYE nableMemoryareaPCICOMMANDMASTERE nableBusmasteringPCICOMMANDSPECIALE nableresponseto specialcyclesPCICOMMANDINVALIDATEU sememorywriteandinvalidatePCICOMMANDVGAP ALETTEE nablevideopaletteaccessPCICOMMANDPARITYE nableparitycheckingPCICOMMANDWAITE nableaddress/datasteppingPCICOMMANDSERRE nableSERRPCICOMMANDFASTBACKE nableback-to-backwritesTable2 nableFeaturesPCISTATUSFASTBACKA cceptfast-backto backPCISTATUSPARITYD etectedparityerrorPCISTATUSDEVSEL[MASK|F AST|MEDIUM|SLOW]

10 DEVSEL timingPCISTATUSSIGTARGETABORTS etontargetabortPCISTATUSRECTARGETABORTM asterackofPCISTATUSRECMASTERABORTS etonmasterabortPCISTATUSSIGSYSTEMERRORS etwhenwedriveSERRPCISTATUSDETECTEDPARITY S etonparityerrorTable3:TheLinuxPCI-Status Bit-SettingsTheLinuxLabProjectwhitepaper s11/1996( )