On Wed, Oct 23, 2013 at 10:42:58AM -0400, Alan Stern wrote:
> On Tue, 22 Oct 2013, Peter Chen wrote:
>
> > For chipidea controller, it does not follow ehci spec strictly.
> > Taking resume signal as an example, it will stop resume signal about
> > 20-21ms later automatically, but standard ehci spec says, the resume
> > signal is controlled by software (clear portsc.PORT_RESUME).
> >
> > This operation causes some remote wakeup problems for high speed
> > devices due to host controller does not send SOF in time since
> > software can't guarantee set run/stop bit in time (run/stop bit
> > was cleared at the ehci suspend routine).
> >
> > When software sets run/stop bit, it needs 1 SoF time to make it effect.
> > If we close the PHY clock just after setting run/stop bit, it does
> > not be set in practice, so a software delay is needed.
> >
> > Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx>
> > ---
> > drivers/usb/chipidea/host.c | 51 +++++++++++++++++++++++++++++++++++++++++++
> > 1 files changed, 51 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> > index 59e6020..283b385 100644
> > --- a/drivers/usb/chipidea/host.c
> > +++ b/drivers/usb/chipidea/host.c
> > @@ -33,6 +33,53 @@
> > #include "host.h"
> >
> > static struct hc_driver __read_mostly ci_ehci_hc_driver;
> > +static int (*orig_bus_suspend)(struct usb_hcd *hcd);
> > +
> > +static int ci_ehci_bus_suspend(struct usb_hcd *hcd)
> > +{
> > + struct ehci_hcd *ehci = hcd_to_ehci(hcd);
> > + int port;
> > + u32 tmp;
> > +
> > + int ret = orig_bus_suspend(hcd);
> > +
> > + if (ret)
> > + return ret;
> > +
> > + port = HCS_N_PORTS(ehci->hcs_params);
> > + while (port--) {
> > + u32 __iomem *reg = &ehci->regs->port_status[port];
> > + u32 portsc = ehci_readl(ehci, reg);
> > +
> > + if (portsc & PORT_CONNECT) {
> > + /*
> > + * For chipidea, the resume signal will be ended
> > + * automatically, so for remote wakeup case, the
> > + * usbcmd.rs may not be set before the resume has
> > + * ended if other resume path consumes too much
> > + * time (~23ms-24ms), in that case, the SOF will not
> > + * send out within 3ms after resume ends, then the
> > + * device will enter suspend again.
> > + */
> > + if (hcd->self.root_hub->do_remote_wakeup) {
> > + ehci_dbg(ehci,
> > + "Remote wakeup is enabled, "
> > + "and device is on the port\n");
> > +
> > + tmp = ehci_readl(ehci, &ehci->regs->command);
> > + tmp |= CMD_RUN;
> > + ehci_writel(ehci, tmp, &ehci->regs->command);
> > + /*
> > + * It needs a short delay between set RUNSTOP
> > + * and set PHCD.
> > + */
> > + udelay(125);
> > + }
> > + }
> > + }
>
> This code is a little strange. If there is only one port then you
> don't need the loop. But if there is more than one port then you don't
> want to put the udelay inside the loop. (If two devices are attached,
> you don't want to delay the suspend by 250 us.)
>
Yes, you are right. I will add break, that is once there is port connected,
delay 125us, then quit while.
--
Best Regards,
Peter Chen
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