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<P>IOS off this hardware and reset if the controller<BR>
* isn't already safely quiescent.<BR>
*/<BR>
check_and_reset_hc(uhci);<BR> return
0;<BR>}<BR>代碼中hcd_to_uhci()的操作就不做詳細分析了.在分配usb_hcd的內存時就已經分析過.<BR>結合UHCI
spec來理解這段代碼.spec中規定.從I/O空間的0x10處開始,為端口控制狀態寄存器(PORTSC).占有兩個字節.這個端口也是指UHCI控制器的root
hub端口.該寄存器用來表示端口的狀態,和操作相應端口.協議中并沒有規定一個UHCI有多少個端口,但規定不能夠超過8個.另外,協議中規定,PORTSC的bit7始終為1.因此可以根據這個特征來判斷端口是否存在.另外,寄存器中的位全為1也是不正常的.<BR>這樣就可以計算出UHCI的root
hub有多少個端口.然后將值存放到uhci的rh_numports中.<BR>注意代碼中取寄存器值的*2操作.這是因為每個PORTSC占兩個字節.<BR>剩下的代碼就只有check_and_reset_hc(
)了.該函數用來檢查UHCI是否需要重置.如果需要重置.那就進行UHCI的重置操作.代碼如下:<BR>static void
check_and_reset_hc(struct uhci_hcd *uhci)<BR>{<BR> if
(uhci_check_and_reset_hc(to_pci_dev(uhci_dev(uhci)),
uhci->io_addr))<BR>
finish_reset(uhci);<BR>}<BR>先來分析uhci_check_and_reset_hc()的代碼.如下所示:<BR>int
uhci_check_and_reset_hc(struct pci_dev *pdev, unsigned long
base)<BR>{<BR> u16 legsup;<BR>
unsigned int cmd, intr;<BR> <BR>
/*<BR> * When restarting a suspended controller,
we expect all the<BR> * settings to be the same as
we left them:<BR> *<BR>
* PIRQ and SMI disabled, no R/W bits set in
USBLEGSUP;<BR> * Controller is stopped
and configured with EGSM set;<BR> * No
interrupts enabled except possibly Resume Detect.<BR>
*<BR> * If any of these conditions are
violated we do a complete reset.<BR>
*/<BR> pci_read_config_word(pdev, UHCI_USBLEGSUP,
&legsup);<BR> if (legsup & ~(UHCI_USBLEGSUP_RO |
UHCI_USBLEGSUP_RWC)) {<BR>
dev_dbg(&pdev->dev, "%s: legsup =
0x%04x\n",<BR>
__FUNCTION__, legsup);<BR> goto
reset_needed;<BR>
}<BR> <BR> cmd = inw(base +
UHCI_USBCMD);<BR> if ((cmd & UHCI_USBCMD_RUN) ||
!(cmd & UHCI_USBCMD_CONFIGURE)
||<BR>
!(cmd & UHCI_USBCMD_EGSM))
{<BR> dev_dbg(&pdev->dev,
"%s: cmd =
0x%04x\n",<BR>
__FUNCTION__, cmd);<BR> goto
reset_needed;<BR>
}<BR> <BR> intr = inw(base +
UHCI_USBINTR);<BR> if (intr &
(~UHCI_USBINTR_RESUME)) {<BR>
dev_dbg(&pdev->dev, "%s: intr =
0x%04x\n",<BR>
__FUNCTION__, intr);<BR> goto
reset_needed;<BR> }<BR> return
0;<BR> <BR>reset_needed:<BR>
dev_dbg(&pdev->dev, "Performing full
reset\n");<BR> uhci_reset_hc(pdev,
base);<BR> return
1;<BR>}<BR>該函數的第一個參數為UHCI對應的pci_dev.第二個參數是I/O區間的起始地址.從代碼中看來,有三種情況是需要重置的.這三種情況分別為:<BR>1:如果LEGACY
SUPPORT REGISTER寄存器中R/W屬性位被置,那就需要重啟. LEGACY SUPPORT REGISTER通常是用于legacy
鍵盤和鼠標.UHCI spec上對其有詳細的定義.對照spec.所有R/W屬性的位都是某種能力的使能開關.例如,bit13表示USB PIRQ
Enable.如果該位被置,表示設備能夠產生中斷.否則就不可以.<BR>因此,對于這樣的位,應該將其初始化.也即將設備的功能關閉.這也很容易理解,為了R/W屬性位被置就需要重啟UHCI<BR> <BR>2:USB
CMD寄存器的UHCI_USBCMD_RUN被置為1,
UHCI_USBCMD_CONFIGURE和UHCI_USBCMD_EGSM位為0的時候需要重啟.<BR>UHCI_USBCMD_RUN表示UHCI正在調度數據,處于運行狀態.顯然,這個時候是應該被重啟的<BR>UHCI_USBCMD_CONFIGURE:這個位是由軟件控制的,只是起一個標識作用,不會對硬件產生任何影響.如果該位為了1,表示UHCI正處于配置狀態.沒有處于配置狀態,當然就可以重啟了.<BR>UHCI_USBCMD_EGSM表示UHCI是否處于Global
Suspend mode.在這種模式下,是不會產生數據交互的.顯然.如果該位為0.則表示該位不是Global Suspend
mode模式,當然就需要重啟了.<BR> <BR>3:USB
INTR寄存器中除UHCI_USBINTR_RESUME如果其它位為1.則重啟UHCI.<BR>在USB INTR寄存器中,bit4~bit15是保留的,始終為0.其它四位對應了UHCI的四種不同類型的中斷,除了bit1表示的Resume
interrupt外,其它類型的應該全部都被關掉.<BR> <BR>如果不需要重啟UHCI,直接返回0即可.如果需要重啟,則會調轉到uhci_reset_hc().代碼如下:<BR>void
uhci_reset_hc(struct pci_dev *pdev, unsigned long
base)<BR>{<BR> /* Turn off PIRQ enable and SMI
enable. (This also turns off the<BR> *
BIOS's USB Legacy Support.) Turn off all the R/WC bits
too.<BR> */<BR>
pci_write_config_word(pdev, UHCI_USBLEGSUP,
UHCI_USBLEGSUP_RWC);<BR> <BR> /* Reset the HC -
this will force us to get a<BR> * new notification
of any already connected<BR> * ports due to the
virtual disconnect that it<BR> *
implies.<BR> */<BR>
outw(UHCI_USBCMD_HCRESET, base + UHCI_USBCMD);<BR>
mb();<BR> udelay(5);<BR> if
(inw(base + UHCI_USBCMD) &
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