linux-kernel - Re: [PATCH 3/8] i2c: i2c-bfin-twi: Break dead waiting loop if i2c device misbehaves.

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Date:	Mon, 11 Jun 2012 18:30:44 +0200
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	sonic.zhang@...log.com
Cc:	Ben Dooks <ben-linux@...ff.org>, linux-i2c@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH 3/8] i2c: i2c-bfin-twi: Break dead waiting loop if i2c
 device misbehaves.

On Wed, May 16, 2012 at 03:20:21PM +0800, sonic.zhang@...log.com wrote:
> From: Sonic Zhang <sonic.zhang@...log.com>
> 
> Some fault i2c device may hold the sda/scl line and cause i2c driver
> wait in the BUS busy loop. This patch breaks this potential dead
> loop.
> 
> Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
> 
> git-svn-id: svn://localhost/svn/linux-kernel/trunk@...1 526b6c2d-f592-4532-a319-5dd88ccb003d

^

> ---
>  drivers/i2c/busses/i2c-bfin-twi.c |   14 ++++++++++++--
>  1 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
> index 376e331..4abaf59 100644
> --- a/drivers/i2c/busses/i2c-bfin-twi.c
> +++ b/drivers/i2c/busses/i2c-bfin-twi.c
> @@ -294,6 +294,8 @@ static irqreturn_t bfin_twi_interrupt_entry(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> +#define BFIN_TWI_BUSY_TIMEOUT	1000
> +

Please use a unit like microseconds for the timeout.

>  /*
>   * One i2c master transfer
>   */
> @@ -303,12 +305,16 @@ static int bfin_twi_do_master_xfer(struct i2c_adapter *adap,
>  	struct bfin_twi_iface *iface = adap->algo_data;
>  	struct i2c_msg *pmsg;
>  	int rc = 0;
> +	unsigned int busy_timeout = BFIN_TWI_BUSY_TIMEOUT;
>  
>  	if (!(read_CONTROL(iface) & TWI_ENA))
>  		return -ENXIO;
>  
> -	while (read_MASTER_STAT(iface) & BUSBUSY)
> +	while (read_MASTER_STAT(iface) & BUSBUSY) {
> +		if (--busy_timeout == 0)
> +			return -EBUSY;
>  		yield();
> +	}
>  
>  	iface->pmsg = msgs;
>  	iface->msg_num = num;
> @@ -403,12 +409,16 @@ int bfin_twi_do_smbus_xfer(struct i2c_adapter *adap, u16 addr,
>  {
>  	struct bfin_twi_iface *iface = adap->algo_data;
>  	int rc = 0;
> +	unsigned int busy_timeout = BFIN_TWI_BUSY_TIMEOUT;
>  
>  	if (!(read_CONTROL(iface) & TWI_ENA))
>  		return -ENXIO;
>  
> -	while (read_MASTER_STAT(iface) & BUSBUSY)
> +	while (read_MASTER_STAT(iface) & BUSBUSY) {
> +		if (--busy_timeout == 0)
> +			return -EBUSY;
>  		yield();
> +	}
>  
>  	iface->writeNum = 0;
>  	iface->readNum = 0;
> -- 
> 1.7.0.4
> 
> 
> --
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-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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