linux-kernel - Re: [Linux-usb-users] OHCI root_port

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Message-Id: <20071016.150834.23011861.davem@davemloft.net>
Date:	Tue, 16 Oct 2007 15:08:34 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	stern@...land.harvard.edu
Cc:	david-b@...bell.net, linux-usb-users@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, greg@...ah.com
Subject: Re: [Linux-usb-users] OHCI root_port_reset() deadly loop...

From: Alan Stern <stern@...land.harvard.edu>
Date: Tue, 16 Oct 2007 11:23:58 -0400 (EDT)

> Do you have any idea _where_ in ohci_hub_control the hang still occurs?  
> Is it the same unbounded reset loop?

Yes, with post status stuck at 0x111

> Does the patch below satisfy both Davids?

No, there are no warning messages that trigger

My last patch was just fine, it timed out appropriately and warned the
user telling them exactly what event timed out.

I'm reposting it here for reference, this is getting silly:

Signed-off-by: David S. Miller <davem@...emloft.net>

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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