PCI裝置驅動之裝置
阿新 • • 發佈：2018-12-17
四、PCI裝置的列舉探測過程
在核心啟動過程中，PCI裝置的探測過程是完全自動的，核心已經整合好了方法，我們無需更改，在這裡還是分析一邊程式碼作為了解。
分析之前，先看一下全部的函式呼叫關係，大致瞭解一下
pci_arch_init /* 判斷host/pci橋的型別 */
pci_direct_probe
pci_check_type1
pci_sanity_check
pci_direct_init
raw_pci_ops = &pci_direct_conf1;
raw_pci_ext_ops = &pci_direct_conf1;
/* 第二個過程，列舉各級總線上的裝置 */ 下面來看具體的探測過程。
static __init int pci_arch_init(void)
{
#ifdef CONFIG_PCI_DIRECT
int type = 0;
type = pci_direct_probe();
#endif
#ifdef CONFIG_PCI_BIOS
pci_pcbios_init();
#endif
#ifdef CONFIG_PCI_DIRECT
pci_direct_init(type);
#endif
dmi_check_pciprobe();
dmi_check_skip_isa_align();
return 0;
}
arch_initcall(pci_arch_init);
這個函式是放在 init 段中，核心啟動時會呼叫。
int __init pci_direct_probe(void)
{
struct resource *region, *region2;
/* 申請IO資源 */
region = request_region(0xCF8, 8, "PCI conf1");
/* 探測那種型別 ，0型（PCI裝置）和1型（PCI橋） */
if (pci_check_type1()) {
raw_pci_ops = &pci_direct_conf1;
port_cf9_safe = true;
return 1;
}
release_resource(region);
type2:
if ((pci_probe & PCI_PROBE_CONF2) == 0)
return 0;
if (!request_region(0xCF8, 4, "PCI conf2"))
return 0;
if (!request_region(0xC000, 0x1000, "PCI conf2"))
goto fail2;
if (pci_check_type2()) {
raw_pci_ops = &pci_direct_conf2;
port_cf9_safe = true;
return 2;
}
release_region(0xC000, 0x1000);
fail2:
release_region(0xCF8, 4);
return 0;
}
在pci規範中,定義了兩種操作配置空間的方法,即type1 和type2.在新的設計中,type2的配置機制不會被採用,通常會使用type1.因此,在程式碼中pci_direct_probe()一般會返回1,即使用type1.
static int __init pci_check_type1(void)
{
unsigned long flags;
unsigned int tmp;
int works = 0;
local_irq_save(flags);
/* i386 pci地址暫存器 0xcfb 寫 0x01 */
outb(0x01, 0xCFB);
tmp = inl(0xCF8);
outl(0x80000000, 0xCF8);
/* 判斷裝置型別 */
if (inl(0xCF8) == 0x80000000 && pci_sanity_check(&pci_direct_conf1)) {
works = 1;
}
outl(tmp, 0xCF8);
local_irq_restore(flags);
return works;
}
static int __init pci_sanity_check(struct pci_raw_ops *o)
{
u32 x = 0;
int year, devfn;
/* Assume Type 1 works for newer systems.
This handles machines that don't have anything on PCI Bus 0. */
dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL);
if (year >= 2001)
return 1;
for (devfn = 0; devfn < 0x100; devfn++) {
/* 讀 CLASS_DEVICE ，PCI_CLASS_DEVICE 是片內偏移地址 */
if (o->read(0, 0, devfn, PCI_CLASS_DEVICE, 2, &x)) //pci_direct_conf1->read
continue;
/* 如果 CLASS_DEVICE 為 HOST-PCI橋（北橋）,PCI-PCI橋,PCI-ISA橋（南橋）正確返回 */
if (x == PCI_CLASS_BRIDGE_HOST || x == PCI_CLASS_DISPLAY_VGA)
return 1;
/* 讀 VENDOR_ID 製造商ID */
if (o->read(0, 0, devfn, PCI_VENDOR_ID, 2, &x))
continue;
/* 如果 VENDOR_ID 為 INTEL 或 COMPAQ 正常返回 */
if (x == PCI_VENDOR_ID_INTEL || x == PCI_VENDOR_ID_COMPAQ)
return 1;
}
DBG(KERN_WARNING "PCI: Sanity check failed\n");
return 0;
}
檢測完是“0型”還是“1型”裝置之後，在 raw_pci_ops 中指定對應的讀寫配置空間的方法。
/* 設定全域性的 配置空間讀寫函式 */
void __init pci_direct_init(int type)
{
if (type == 1) {
raw_pci_ops = &pci_direct_conf1;
raw_pci_ext_ops = &pci_direct_conf1;
return;
}
}
/* 地址是由 匯流排編號、裝置號、片內地址 組成 */
#define PCI_CONF1_ADDRESS(bus, devfn, reg) \
(0x80000000 | ((reg & 0xF00) << 16) | (bus << 16) \
| (devfn << 8) | (reg & 0xFC))
static int pci_conf1_read(unsigned int seg, unsigned int bus,
unsigned int devfn, int reg, int len, u32 *value)
{
unsigned long flags;
/* 最多256個匯流排 ，256個裝置 片內暫存器範圍 0~4095 */
if ((bus > 255) || (devfn > 255) || (reg > 4095)) {
*value = -1;
return -EINVAL;
}
spin_lock_irqsave(&pci_config_lock, flags);
/* 向地址暫存器 寫要讀取的地址 */
outl(PCI_CONF1_ADDRESS(bus, devfn, reg), 0xCF8);
/* 從資料暫存器讀取資料 */
switch (len) {
case 1:
*value = inb(0xCFC + (reg & 3));
break;
case 2:
*value = inw(0xCFC + (reg & 2));
break;
case 4:
*value = inl(0xCFC);
break;
}
spin_unlock_irqrestore(&pci_config_lock, flags);
return 0;
}
struct pci_raw_ops {
int (*read)(unsigned int domain, unsigned int bus, unsigned int devfn,
int reg, int len, u32 *val);
int (*write)(unsigned int domain, unsigned int bus, unsigned int devfn,
int reg, int len, u32 val);
};
struct pci_raw_ops *raw_pci_ops;
五:pci裝置的列舉過程
int __init pci_subsys_init(void)
{
#ifdef CONFIG_X86_NUMAQ
pci_numaq_init();
#endif
#ifdef CONFIG_ACPI
pci_acpi_init();
#endif
#ifdef CONFIG_X86_VISWS
pci_visws_init();
#endif
pci_legacy_init();
pcibios_fixup_peer_bridges();
pcibios_irq_init();
pcibios_init();
return 0;
}
subsys_initcall(pci_subsys_init);
struct pci_bus *pci_root_bus;
static int __init pci_legacy_init(void)
{
pci_root_bus = pcibios_scan_root(0);//建立0級匯流排
if (pci_root_bus)
pci_bus_add_devices(pci_root_bus);
return 0;
}
extern struct list_head pci_root_buses; /* list of all known PCI buses */
struct pci_bus * __devinit pcibios_scan_root(int busnum)
{
struct pci_bus *bus = NULL;
struct pci_sysdata *sd;
/* 在全域性 pci_root_buses 連結串列尋找 匯流排編號為 busnum 的匯流排 */
while ((bus = pci_find_next_bus(bus)) != NULL) {
if (bus->number == busnum) {
/* 如果已經存在，返回它 */
return bus;
}
}
/* 如果這個匯流排編號不存在, 那麼建立這個Bus */
sd = kzalloc(sizeof(*sd), GFP_KERNEL);
sd->node = get_mp_bus_to_node(busnum);
bus = pci_scan_bus_parented(NULL, busnum, &pci_root_ops, sd);
return bus;
}
struct pci_bus * __devinit pci_scan_bus_parented(struct device *parent,
int bus, struct pci_ops *ops, void *sysdata)
{
struct pci_bus *b;
/* 為對應匯流排號構建pci_bus,然後將其掛入到pci_root_buses連結串列 */
b = pci_create_bus(parent, bus, ops, sysdata);
if (b)
b->subordinate = pci_scan_child_bus(b);
return b;
}
unsigned int __devinit pci_scan_child_bus(struct pci_bus *bus)
{
unsigned int devfn, pass, max = bus->secondary;
struct pci_dev *dev;
/* 探測總線上的裝置,按功能號掃描裝置號對應的pci 裝置 */
for (devfn = 0; devfn < 0x100; devfn += 8)
pci_scan_slot(bus, devfn);
/* Reserve buses for SR-IOV capability. */
max += pci_iov_bus_range(bus);
/*
* After performing arch-dependent fixup of the bus, look behind
* all PCI-to-PCI bridges on this bus.
*/
if (!bus->is_added) {
pr_debug("PCI: Fixups for bus %04x:%02x\n",
pci_domain_nr(bus), bus->number);
pcibios_fixup_bus(bus);
if (pci_is_root_bus(bus))
bus->is_added = 1;
}
/* 探測 pci 橋上的裝置，建立子Bus，掛到父 bus->child */
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;
}
這節的難點就是在這個地方了,從我們之前分析的pci裝置配置空間的讀寫方式可得知.對特定匯流排.下面最多個32個裝置號.每個裝置號又對應8 個功能號.我們可以將裝置號和功能號放到一起,即佔8~15位.在這面的程式碼中.對每個裝置號呼叫pci_scan_slot()去掃描它下面的8個功能號對應的裝置.總而言之,把該匯流排下面的所有裝置都要列舉完.
int pci_scan_slot(struct pci_bus *bus, int devfn)
{
int fn, nr = 0;
struct pci_dev *dev;
dev = pci_scan_single_device(bus, devfn);
/* 如果是多功能裝置 */
if (dev && dev->multifunction) {
for (fn = 1; fn < 8; fn++) {
dev = pci_scan_single_device(bus, devfn + fn);
if (dev) {
if (!dev->is_added)
nr++;
dev->multifunction = 1;
}
}
}
return nr;
}
struct pci_dev *__ref pci_scan_single_device(struct pci_bus *bus, int devfn)
{
struct pci_dev *dev;
/* 遍歷 bus->devices 裝置連結串列，查詢是否有 devfn 號裝置存在 */
dev = pci_get_slot(bus, devfn);
/* 如果已經存在，返回它 */
if (dev) {
pci_dev_put(dev);
return dev;
}
/* 通過訪問配置空間，探測裝置 */
dev = pci_scan_device(bus, devfn);
/* 探測失敗 返回Null */
if (!dev)
return NULL;
/* 探測成功 */
pci_device_add(dev, bus);
return dev;
}
呼叫pci_scan_device()執行掃描的過程,如果該裝置存在,就會將該裝置加入到所屬匯流排的devices連結串列上.這是在pci_device_add()函式中完成的,這個函式比較簡單.這裡不做詳細分析.我們把注意力集中到pci_scan_device(),這函式有點長,分段分析如下:
static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
{
struct pci_dev *dev;
u32 l;
int delay = 1;
/* 讀 PCI_VENDOR_ID 製造商ID */
if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l))
return NULL;
/* id 等於這些值，認為探測失敗 ，返回 */
if (l == 0xffffffff || l == 0x00000000 ||
l == 0x0000ffff || l == 0xffff0000)
return NULL;
....
/* 探測成功，分配一個 pci_dev 結構 */
dev = alloc_pci_dev();
dev->bus = bus;
dev->devfn = devfn;
dev->vendor = l & 0xffff;
dev->device = (l >> 16) & 0xffff;
/* 讀取配置空間，更詳細的設定，指定 dev->bus 等 */
if (pci_setup_device(dev)) {
kfree(dev);
return NULL;
}
return dev;
}
從配置空間中讀取該裝置對應的vendor id和device id.如果讀出來的值,有一個是空的,則說明該功能號對應的裝置不存在,或者是配置非法.
如果讀出來的是0xffff0001.則需要重新讀一次,如果重讀次數過多,也會退出
//對特定型別的裝置配置都行讀取操作
int pci_setup_device(struct pci_dev *dev)
{
u32 class;
u8 hdr_type;
struct pci_slot *slot;
dev->sysdata = dev->bus->sysdata;
dev->dev.parent = dev->bus->bridge;
/* 設定 dev 所屬的匯流排 */
dev->dev.bus = &pci_bus_type;
dev->hdr_type = hdr_type & 0x7f;
dev->multifunction = !!(hdr_type & 0x80);
dev->error_state = pci_channel_io_normal;
set_pcie_port_type(dev);
list_for_each_entry(slot, &dev->bus->slots, list)
if (PCI_SLOT(dev->devfn) == slot->number)
dev->slot = slot;
dev->dma_mask = 0xffffffff;
/* 裝置名 */
dev_set_name(&dev->dev, "%04x:%02x:%02x.%d", pci_domain_nr(dev->bus),
dev->bus->number, PCI_SLOT(dev->devfn),
PCI_FUNC(dev->devfn));
/* 裝置型別 */
pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
dev->revision = class & 0xff;
class >>= 8; /* upper 3 bytes */
dev->class = class;
class >>= 8;
/* need to have dev->class ready */
dev->cfg_size = pci_cfg_space_size(dev);
/* "Unknown power state" */
dev->current_state = PCI_UNKNOWN;
/* Early fixups, before probing the BARs */
pci_fixup_device(pci_fixup_early, dev);
/* device class may be changed after fixup */
class = dev->class >> 8;
switch (dev->hdr_type) { /* header type */
case PCI_HEADER_TYPE_NORMAL: /* standard header */
...
case PCI_HEADER_TYPE_BRIDGE: /* bridge header */
/* 設定 de