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

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Message-ID: <20120814075806.GA32585@arwen.pp.htv.fi>
Date:	Tue, 14 Aug 2012 10:58:07 +0300
From:	Felipe Balbi <balbi@...com>
To:	NeilBrown <neilb@...e.de>
Cc:	balbi@...com, 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 Tue, Aug 14, 2012 at 07:46:59AM +1000, NeilBrown wrote:
> On Mon, 13 Aug 2012 17:32:34 +0300 Felipe Balbi <balbi@...com> wrote:
> 
> > Hi,
> > 
> > On Mon, Aug 13, 2012 at 12:34:53PM +1000, NeilBrown wrote:
> > > 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);
> > 
> > I would prefer udelay_range() as it will let scheduler group timers.
> > Something like:
> > 
> > udelay_range(3000, 5000);
> > 
> > should do, I gues...
> > 
> 
> Except that there is no udelay_range :-(
> There is a usleep_range, but that can only be used from non-atomic context
> and in the problem case interrupts are disabled and a spinlock is held so we

my bad. Got confused. I will apply the original patch then. Thanks.

-- 
balbi

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