On 06.01.2016 20:45, Laurent Vivier wrote: > On overcommitted CPU, kernel can be so slow that an interrupt can > be triggered by the device whereas the driver is not ready to receive > it. This drives us into an infinite loop. > > On suspend, if a SOF interrupt is raised between the stop of the > device processing and the change of the device internal state to > OHCI_USB_SUSPEND (QEMU stops SOF timer on this state change), this > interrupt is never acknowledged. > > This patch clears pending SOF interrupt on OHCI_USB_SUSPEND setting. > > Some details: > > - ohci_irq(): the OHCI interrupt handler, acknowledges the SOF IRQ > only if the state of the driver (rh_state) is OHCI_STATE_RUNNING. > So if this interrupt happens and the driver is not in this state, > the function is called again and again, moving the system to a > CPU starvation. > > - ohci_rh_suspend(): the function stop the operation and acknowledge > pending interrupts (but doesn't disable it). Later in the function, > the device is moved to OHCI_SUSPEND_STATE, and the driver to > OHCI_RH_SUSPENDED. If between the moment when the interrupt is > acknowledged and the moment when the device is suspended a new > interrupt is raised, it will be never acknowledged because the > driver is now not in OHCI_RH_RUNNING state. > > Signed-off-by: Laurent Vivier <[email protected]> > --- > hw/usb/hcd-ohci.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c > index a44fab2..b99e44f 100644 > --- a/hw/usb/hcd-ohci.c > +++ b/hw/usb/hcd-ohci.c > @@ -1446,6 +1446,9 @@ static void ohci_set_ctl(OHCIState *ohci, uint32_t val) > break; > case OHCI_USB_SUSPEND: > ohci_bus_stop(ohci); > + /* clear pending SF otherwise linux driver loops in ohci_irq() */ > + ohci->intr_status &= ~OHCI_INTR_SF; > + ohci_intr_update(ohci); > break; > case OHCI_USB_RESUME: > trace_usb_ohci_resume(ohci->name); >
Reviewed-by: Thomas Huth <[email protected]>
