From: David Brownell <[email protected]>
Date: Mon, 08 Oct 2007 21:36:43 -0700
> Don't need this "limit_1" timeout; "reset_done" handles all
> the timeout needed there. The regs->fmnumber is essentially
> a millisecond counter.
If the hardware hangs and the register stops incrementing,
the entire kernel will hang. That is unacceptable.
We do need it.
>
> > + int limit_2;
> > +
> > /* spin until any current reset finishes */
> > - for (;;) {
> > + limit_2 = PORT_RESET_MSEC * 2;
>
> This is the loop that didn't terminate for you, right?
> PORT_RESET_HW_MSEC is the ceiling you should use here,
> not PORT_RESET_MSEC.
Ok, fixed.
> What values do you see for "portstat"?
0x111
> I suspect there will be some flag set which would allow a more
> immediate exit from that loop. RH_PS_CCS might clear, for example.
Absolutely nothing clears in the register from it's initial value.
Here is the patch with the limit_2 initial value fixed.
I kept loop_1 in there, it is necessary. No kernel code should
hang in an endless loop because of malfunctioning hardware.
Signed-off-by: David S. Miller <[email protected]>
diff --git a/drivers/usb/host/ohci-hub.c b/drivers/usb/host/ohci-hub.c
index bb9cc59..9149593 100644
--- a/drivers/usb/host/ohci-hub.c
+++ b/drivers/usb/host/ohci-hub.c
@@ -563,14 +563,19 @@ static inline int root_port_reset (struct ohci_hcd *ohci, unsigned port)
u32 temp;
u16 now = ohci_readl(ohci, &ohci->regs->fmnumber);
u16 reset_done = now + PORT_RESET_MSEC;
+ int limit_1;
/* build a "continuous enough" reset signal, with up to
* 3msec gap between pulses. scheduler HZ==100 must work;
* this might need to be deadline-scheduled.
*/
- do {
+ limit_1 = 100;
+ while (--limit_1 >= 0) {
+ int limit_2;
+
/* spin until any current reset finishes */
- for (;;) {
+ limit_2 = PORT_RESET_HW_MSEC * 2;
+ while (--limit_2 >= 0) {
temp = ohci_readl (ohci, portstat);
/* handle e.g. CardBus eject */
if (temp == ~(u32)0)
@@ -579,6 +584,10 @@ static inline int root_port_reset (struct ohci_hcd *ohci, unsigned port)
break;
udelay (500);
}
+ if (limit_2 < 0) {
+ ohci_warn(ohci, "Root port inner-loop reset timeout, "
+ "portstat[%08x]\n", temp);
+ }
if (!(temp & RH_PS_CCS))
break;
@@ -589,7 +598,14 @@ static inline int root_port_reset (struct ohci_hcd *ohci, unsigned port)
ohci_writel (ohci, RH_PS_PRS, portstat);
msleep(PORT_RESET_HW_MSEC);
now = ohci_readl(ohci, &ohci->regs->fmnumber);
- } while (tick_before(now, reset_done));
+ if (!tick_before(now, reset_done))
+ break;
+ }
+ if (limit_1 < 0) {
+ ohci_warn(ohci, "Root port outer-loop reset timeout, "
+ "now[%04x] reset_done[%04x]\n",
+ now, reset_done);
+ }
/* caller synchronizes using PRSC */
return 0;
-
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