Hi Peter and Rechard, On Fri, May 18, 2012 at 6:33 PM, Chen Peter-B29397 <B29397@xxxxxxxxxxxxx> wrote: > > Hi Ming, > > I have debugged it at this afternoon, your description for this problem > is correct, the ehci_reset override the ehci->command which is assigned > at ehci_init, and ehci->command at ehci_init is correct. > > My opinion for this fix is just remove the > " ehci->command = ehci_readl(ehci, &ehci->regs->command);" at ehci_reset. > Even someone called ehci_reset to reset controller, it can still use command > value assigned at ehci_init. After some check, I agree with you on fixing the problem by removing the line in ehci_reset. In fact, this line may introduce same overriding problem because CMD register will be restored to its default value per ehci spec[1]. And some ehci drivers may run ehci_reset during resume(for example, pci_ehci/ehci_fsl, see ehci_pci_resume,...). [1], 4.1 Host Controller Initialization of EHCI Specification 1.0 So could you test the below patch? -- diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index f644ba9..5597e60 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -352,7 +352,6 @@ static int ehci_reset (struct ehci_hcd *ehci) if (ehci->debug) dbgp_external_startup(); - ehci->command = ehci_readl(ehci, &ehci->regs->command); ehci->port_c_suspend = ehci->suspended_ports = ehci->resuming_ports = 0; return retval; Alan, any comments on the patch? Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
