>
> Anatolij and others:
>
> Can you explain why the ehci_fsl_mpc512x_drv_suspend() routine goes to
> the trouble of turning off the CMD_RUN bit in the EHCI command
> register, and why ehci_fsl_mpc512x_drv_resume() turns it back on?
>
> These routines handle power management for the EHCI controller. At the
> time they run, the root hub is guaranteed to be suspended -- that is,
> ehci_bus_suspend() has run and ehci_bus_resume() hasn't been called
> yet. As a result, the CMD_RUN bit should already be off and it should
> remain off.
>
> Would it be okay for me to remove the code that changes the CMD_RUN
> bit?
>
At fsl driver, the controller suspend/resume routine is not only used at system pm
routine, but also for OTG ID switch, it needs to save/restore registers as udc driver
will change it. I (I work at ARM platform) guess operation for CMD_RUN is to make sure
CMD_RUN is 0 before switch to device mode, set CMD_RUN to 1 before host wants to run.
> Also, why does the resume routine call usb_hcd_resume_root_hub()? Is
> there a hardware bug that causes the controller not to issue the proper
> IRQ when a root-hub wakeup event occurs?
>
The reason is when CMD_RUN is 1, the usb_hcd_resume_root_hub will not be called at PCD interrupt.
The last four lines of code at ehci_fsl_mpc512x_drv_resume may be commented since pcd interrupt
will be occurred after vbus is on.
tmp = ehci_readl(ehci, &ehci->regs->command);
tmp |= CMD_RUN;
ehci_writel(ehci, tmp, &ehci->regs->command);
usb_hcd_resume_root_hub(hcd);
> Alan Stern
>
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