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

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Message-ID: <20120813143233.GJ14781@arwen.pp.htv.fi>
Date:	Mon, 13 Aug 2012 17:32:34 +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

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...

-- 
balbi

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