这里讨论系统上电时的情况, 热插拔的情况应该差不多.
首先是从根总线开始, 然后就是扫描这个根总线上的每一条子BUS, 如下:
unsigned int pci_scan_child_bus(struct pci_bus *bus)
{
unsigned int devfn, pass, max = bus->secondary;
struct pci_dev *dev;
pr_debug("PCI: Scanning bus %04x:%02x\n", pci_domain_nr(bus), bus->number);
/* Go find them, Rover! */
这里循环256(0x100)/8 = 32次的意思是, 每个总线可能有32个设备,
而每个设备可能是多功能的, 且最多有8个功能.
for (devfn = 0; devfn < 0x100; devfn += 8)
pci_scan_slot(bus, devfn);
//下面在递归扫描PCI桥,不是我们要关心的.
/*
* After performing arch-dependent fixup of the bus, look behind
* all PCI-to-PCI bridges on this bus.
*/
pr_debug("PCI: Fixups for bus %04x:%02x\n", pci_domain_nr(bus), bus->number);
pcibios_fixup_bus(bus);
for (pass=0; pass < 2; pass++)
list_for_each_entry(dev, &bus->devices, bus_list) {
if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
dev->hdr_type == PCI_HEADER_TYPE_CARDBUS)
max = pci_scan_bridge(bus, dev, max, pass);
}
/*
* We've scanned the bus and so we know all about what's on
* the other side of any bridges that may be on this bus plus
* any devices.
*
* Return how far we've got finding sub-buses.
*/
pr_debug("PCI: Bus scan for %04x:%02x returning with max=%02x\n",
pci_domain_nr(bus), bus->number, max);
return max;
}
/**
* pci_scan_slot - scan a PCI slot on a bus for devices.
* @bus: PCI bus to scan
* @devfn: slot number to scan (must have zero function.)
*
* Scan a PCI slot on the specified PCI bus for devices, adding
* discovered devices to the @bus->devices list. New devices
* will have an empty dev->global_list head.
*/
int pci_scan_slot(struct pci_bus *bus, int devfn)
{
int func, nr = 0;
int scan_all_fns;
//空函数
scan_all_fns = pcibios_scan_all_fns(bus, devfn);
//每个设备可能有8个功能
for (func = 0; func < 8; func++, devfn++) {
struct pci_dev *dev;
//分配并初始化找到的设备
dev = pci_scan_single_device(bus, devfn);
if (dev) {
nr++;
/*
* If this is a single function device,
* don't scan past the first function.
*/
if (!dev->multifunction) {
if (func > 0) {
dev->multifunction = 1;
} else {
break;
}
}
} else {
if (func == 0 && !scan_all_fns)
break;
}
}
return nr;
}
struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn)
{
struct pci_dev *dev;
//扫描设备, 如果存在, 分配一个结构,
//并读取这个设备的寄存器信息将其初始化
dev = pci_scan_device(bus, devfn);
if (!dev)
return NULL;
//将设备加入的bus总线
pci_device_add(dev, bus);
return dev;
}
/*
* Read the config data for a PCI device, sanity-check it
* and fill in the dev structure...
*/
这个函数的功能上面的注释已经说明白了
static struct pci_dev * __devinit
pci_scan_device(struct pci_bus *bus, int devfn)
{
struct pci_dev *dev;
u32 l;
u8 hdr_type;
int delay = 1;
//两个检查
if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l))
return NULL;
/* some broken boards return 0 or ~0 if a slot is empty: */
if (l == 0xffffffff || l == 0x00000000 ||
l == 0x0000ffff || l == 0xffff0000)
return NULL;
/* Configuration request Retry Status */
while (l == 0xffff0001) {
msleep(delay);
delay *= 2;
if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l))
return NULL;
/* Card hasn't responded in 60 seconds? Must be stuck. */
if (delay > 60 * 1000) {
printk(KERN_WARNING "Device %04x:%02x:%02x.%d not "
"responding\n", pci_domain_nr(bus),
bus->number, PCI_SLOT(devfn),
PCI_FUNC(devfn));
return NULL;
}
}
//读PCI类型信息, PCI_HEADER_TYPE是在这个寄存器中的偏移值
//可能的类型信息如下:
#define PCI_HEADER_TYPE 0x0e /* 8 bits */
#define PCI_HEADER_TYPE_NORMAL 0
#define PCI_HEADER_TYPE_BRIDGE 1
#define PCI_HEADER_TYPE_CARDBUS 2
if (pci_bus_read_config_byte(bus, devfn, PCI_HEADER_TYPE, &hdr_type))
return NULL;
//如果上面的成功了, 则为设备分配一个pci_dev结构,
//我们在写驱动的时候看到, 在调用probe函数是, 参数传入的就是这里得到的结构.
//这个结构在这个函数里面已经初始化好了.
dev = alloc_pci_dev();
if (!dev)
return NULL;
//初步初始化一些域
dev->bus = bus;
dev->sysdata = bus->sysdata;
dev->dev.parent = bus->bridge;
dev->dev.bus = &pci_bus_type;
dev->devfn = devfn;
dev->hdr_type = hdr_type & 0x7f;
dev->multifunction = !!(hdr_type & 0x80);
dev->vendor = l & 0xffff;
dev->device = (l >> 16) & 0xffff;
dev->cfg_size = pci_cfg_space_size(dev); // 用于PCI-X
dev->error_state = pci_channel_io_normal;
/* Assume 32-bit PCI; let 64-bit PCI cards (which are far rarer)
set this higher, assuming the system even supports it. */
dev->dma_mask = 0xffffffff; //32为DMA
//进一步初始化, 数据来自于寄存器
if (pci_setup_device(dev) < 0) {
kfree(dev);
return NULL;
}
return dev;
}
//分配一个结构并初始化两个队列
struct pci_dev *alloc_pci_dev(void)
{
struct pci_dev *dev;
dev = kzalloc(sizeof(struct pci_dev), GFP_KERNEL);
if (!dev)
return NULL;
INIT_LIST_HEAD(&dev->global_list);
INIT_LIST_HEAD(&dev->bus_list);
pci_msi_init_pci_dev(dev);
return dev;
}
struct bus_type pci_bus_type = {
.name = "pci",
.match = pci_bus_match,
.uevent = pci_uevent,
.probe = pci_device_probe,
.remove = pci_device_remove,
.suspend = pci_device_suspend,
.suspend_late = pci_device_suspend_late,
.resume_early = pci_device_resume_early,
.resume = pci_device_resume,
.shutdown = pci_device_shutdown,
.dev_attrs = pci_dev_attrs,
};
/**
* pci_setup_device - fill in class and map information of a device
* @dev: the device structure to fill
*
* Initialize the device structure with information about the device's
* vendor,class,memory and IO-space addresses,IRQ lines etc.
* Called at initialisation of the PCI subsystem and by CardBus services.
* Returns 0 on success and -1 if unknown type of device (not normal, bridge
* or CardBus).
*/
这个函数比较简单, 可以看注释,就不说了
static int pci_setup_device(struct pci_dev * dev)
{
u32 class;
sprintf(pci_name(dev), "%04x:%02x:%02x.%d", pci_domain_nr(dev->bus),
dev->bus->number, PCI_SLOT(dev->devfn), PCI_FUNC(dev->devfn));
pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
class >>= 8; /* upper 3 bytes */
dev->class = class;
class >>= 8;
pr_debug("PCI: Found %s [%04x/%04x] %06x %02x\n", pci_name(dev),
dev->vendor, dev->device, class, dev->hdr_type);
/* "Unknown power state" */
dev->current_state = PCI_UNKNOWN;
/* Early fixups, before probing the BARs */
pci_fixup_device(pci_fixup_early, dev);
class = dev->class >> 8;
switch (dev->hdr_type) { /* header type */
case PCI_HEADER_TYPE_NORMAL: /* standard header */
if (class == PCI_CLASS_BRIDGE_PCI)
goto bad;
pci_read_irq(dev);
pci_read_bases(dev, 6, PCI_ROM_ADDRESS);
pci_read_config_word(dev, PCI_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
pci_read_config_word(dev, PCI_SUBSYSTEM_ID, &dev->subsystem_device);
/*
* Do the ugly legacy mode stuff here rather than broken chip
* quirk code. Legacy mode ATA controllers have fixed
* addresses. These are not always echoed in BAR0-3, and
* BAR0-3 in a few cases contain junk!
*/
if (class == PCI_CLASS_STORAGE_IDE) {
u8 progif;
pci_read_config_byte(dev, PCI_CLASS_PROG, &progif);
if ((progif & 1) == 0) {
dev->resource[0].start = 0x1F0;
dev->resource[0].end = 0x1F7;
dev->resource[0].flags = LEGACY_IO_RESOURCE;
dev->resource[1].start = 0x3F6;
dev->resource[1].end = 0x3F6;
dev->resource[1].flags = LEGACY_IO_RESOURCE;
}
if ((progif & 4) == 0) {
dev->resource[2].start = 0x170;
dev->resource[2].end = 0x177;
dev->resource[2].flags = LEGACY_IO_RESOURCE;
dev->resource[3].start = 0x376;
dev->resource[3].end = 0x376;
dev->resource[3].flags = LEGACY_IO_RESOURCE;
}
}
break;
case PCI_HEADER_TYPE_BRIDGE: /* bridge header */
if (class != PCI_CLASS_BRIDGE_PCI)
goto bad;
/* The PCI-to-PCI bridge spec requires that subtractive
decoding (i.e. transparent) bridge must have programming
interface code of 0x01. */
pci_read_irq(dev);
dev->transparent = ((dev->class & 0xff) == 1);
pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
break;
case PCI_HEADER_TYPE_CARDBUS: /* CardBus bridge header */
if (class != PCI_CLASS_BRIDGE_CARDBUS)
goto bad;
pci_read_irq(dev);
pci_read_bases(dev, 1, 0);
pci_read_config_word(dev, PCI_CB_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
pci_read_config_word(dev, PCI_CB_SUBSYSTEM_ID, &dev->subsystem_device);
break;
default: /* unknown header */
printk(KERN_ERR "PCI: device %s has unknown header type %02x, ignoring.\n",
pci_name(dev), dev->hdr_type);
return -1;
bad:
printk(KERN_ERR "PCI: %s: class %x doesn't match header type %02x. Ignoring
class.\n",
pci_name(dev), class, dev->hdr_type);
dev->class = PCI_CLASS_NOT_DEFINED;
}
/* We found a fine healthy device, go go go... */
return 0;
}
设备初始化完成后, 我们就回到了pci_scan_single_device()这个函数,
下一步就是将这个分配好的设备加入的bus队列中去了.
void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
{
device_initialize(&dev->dev);
dev->dev.release = pci_release_dev;
pci_dev_get(dev);
set_dev_node(&dev->dev, pcibus_to_node(bus));
dev->dev.dma_mask = &dev->dma_mask;
dev->dev.coherent_dma_mask = 0xffffffffull;
/* Fix up broken headers */
pci_fixup_device(pci_fixup_header, dev);
/*
* Add the device to our list of discovered devices
* and the bus list for fixup functions, etc.
*/
INIT_LIST_HEAD(&dev->global_list);
down_write(&pci_bus_sem);
list_add_tail(&dev->bus_list, &bus->devices); //加入到bus的device队列
up_write(&pci_bus_sem);
}
/**
* device_initialize - init device structure.
* @dev: device.
*
* This prepares the device for use by other layers,
* including adding it to the device hierarchy.
* It is the first half of device_register(), if called by
* that, though it can also be called separately, so one
* may use @dev's fields (e.g. the refcount).
*/
void device_initialize(struct device *dev)
{
//属于devices_subsys子系统
kobj_set_kset_s(dev, devices_subsys);
//以下是初始化一下队列, 如等待队列
kobject_init(&dev->kobj);
klist_init(&dev->klist_children, klist_children_get,
klist_children_put);
INIT_LIST_HEAD(&dev->dma_pools);
INIT_LIST_HEAD(&dev->node);
init_MUTEX(&dev->sem);
spin_lock_init(&dev->devres_lock);
INIT_LIST_HEAD(&dev->devres_head);
device_init_wakeup(dev, 0);
set_dev_node(dev, -1);
}
