linux-kernel - Re: Infinite looping in omap2430.c USB driver

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Message-ID: <20120813123453.4cba14ca@notabene.brown>
Date:	Mon, 13 Aug 2012 12:34:53 +1000
From:	NeilBrown <neilb@...e.de>
To:	balbi@...com
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Infinite looping in omap2430.c USB driver

On Thu, 9 Aug 2012 14:15:51 +0300 Felipe Balbi <balbi@...com> wrote:


> hehe, that's nasty. Please send a patch converting to a try count and a
> udelay_range(), or something.
> 

how's this?

Thanks,
NeilBrown


From: NeilBrown <neilb@...e.de>
Date: Mon, 13 Aug 2012 12:32:58 +1000
Subject: [PATCH] omap2430: don't loop indefinitely in interrupt.

When called during resume_irqs, omap2430_musb_set_vbus() is run with
interrupts disabled,  In that case 'jiffies' never changes so the loop
can loop forever.

So impose a maximum loop count and add an 'mdelay' to ensure we wait
a reasonable amount of time for bit to be cleared.

This fixes a hang on resume.

Signed-of-by: NeilBrown <neilb@...e.de>

diff --git a/drivers/usb/musb/omap2430.c b/drivers/usb/musb/omap2430.c
index c7785e8..8a93381 100644
--- a/drivers/usb/musb/omap2430.c
+++ b/drivers/usb/musb/omap2430.c
@@ -34,6 +34,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/pm_runtime.h>
 #include <linux/err.h>
+#include <linux/delay.h>
 
 #include "musb_core.h"
 #include "omap2430.h"
@@ -145,6 +146,7 @@ static void omap2430_musb_set_vbus(struct musb *musb, int is_on)
 
 	if (is_on) {
 		if (musb->xceiv->state == OTG_STATE_A_IDLE) {
+			int loops = 100;
 			/* start the session */
 			devctl |= MUSB_DEVCTL_SESSION;
 			musb_writeb(musb->mregs, MUSB_DEVCTL, devctl);
@@ -154,9 +156,11 @@ static void omap2430_musb_set_vbus(struct musb *musb, int is_on)
 			 */
 			while (musb_readb(musb->mregs, MUSB_DEVCTL) & 0x80) {
 
+				mdelay(5);
 				cpu_relax();
 
-				if (time_after(jiffies, timeout)) {
+				if (time_after(jiffies, timeout)
+				    || loops-- <= 0) {
 					dev_err(musb->controller,
 					"configured as A device timeout");
 					ret = -EINVAL;

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