Subject: Re: [RFC] I2C-MPC: Fix up error handling

From: Jean Delvare <[email-masked]>
Date: Sun, 30 Jul 2006 13:14:40 +0200

Quoting myself:
> Could anyone please comment on this i2c-mpc patch, and give it some
> testing on different systems? I'm fine with the error propagation
> fixes, but less fine with the random resets being added, and rather
> unhappy with the "retry once more just in case" thing, which I think,
> if really needed, should instead be implemented using the standard
> i2c_adapter.retries mechanism.

Can anyone please comment on this patch? Andrew Morton keeps forwarding
it to me, but I don't think I can accept it as is (see my complaints
above.)

> From: Kumar Gala <[email-masked]>
> 
> * If we have an Unfinished (MCF) or Arbitration Lost (MAL) error and
>   the bus is still busy reset the controller.  This prevents the
>   controller from getting in a hung state for transactions for other
>   devices.
> 
> * Fixed up propogating the errors from i2c_wait.
> 
> Signed-off-by: Kumar Gala <[email-masked]>
> Cc: Jean Delvare <[email-masked]>
> Cc: Greg KH <[email-masked]>
> Signed-off-by: Andrew Morton <[email-masked]>
> ---
> 
>  drivers/i2c/busses/i2c-mpc.c |   43 +++++++++++++++++++++++----------
>  1 file changed, 31 insertions(+), 12 deletions(-)
> 
> diff -puN drivers/i2c/busses/i2c-mpc.c~i2c-mpc-fix-up-error-handling drivers/i2c/busses/i2c-mpc.c
> --- devel/drivers/i2c/busses/i2c-mpc.c~i2c-mpc-fix-up-error-handling	2006-06-01 20:22:55.000000000 -0700
> +++ devel-akpm/drivers/i2c/busses/i2c-mpc.c	2006-06-01 20:22:55.000000000 -0700
> @@ -115,11 +115,20 @@ static int i2c_wait(struct mpc_i2c *i2c,
>  
>  	if (!(x & CSR_MCF)) {
>  		pr_debug("I2C: unfinished\n");
> +
> +		/* reset the controller if the bus is still busy */
> +		if (x & CSR_MBB)
> +			writeccr(i2c, 0);
> +
>  		return -EIO;
>  	}
>  
>  	if (x & CSR_MAL) {
>  		pr_debug("I2C: MAL\n");
> +
> +		/* reset the controller if the bus is still busy */
> +		if (x & CSR_MBB)
> +			writeccr(i2c, 0);
>  		return -EIO;
>  	}
>  
> @@ -160,7 +169,7 @@ static void mpc_i2c_stop(struct mpc_i2c 
>  static int mpc_write(struct mpc_i2c *i2c, int target,
>  		     const u8 * data, int length, int restart)
>  {
> -	int i;
> +	int i, ret;
>  	unsigned timeout = i2c->adap.timeout;
>  	u32 flags = restart ? CCR_RSTA : 0;
>  
> @@ -172,15 +181,17 @@ static int mpc_write(struct mpc_i2c *i2c
>  	/* Write target byte */
>  	writeb((target << 1), i2c->base + MPC_I2C_DR);
>  
> -	if (i2c_wait(i2c, timeout, 1) < 0)
> -		return -1;
> +	ret = i2c_wait(i2c, timeout, 1);
> +	if (ret < 0)
> +		return ret;
>  
>  	for (i = 0; i < length; i++) {
>  		/* Write data byte */
>  		writeb(data[i], i2c->base + MPC_I2C_DR);
>  
> -		if (i2c_wait(i2c, timeout, 1) < 0)
> -			return -1;
> +		ret = i2c_wait(i2c, timeout, 1);
> +		if (ret < 0)
> +			return ret;
>  	}
>  
>  	return 0;
> @@ -190,7 +201,7 @@ static int mpc_read(struct mpc_i2c *i2c,
>  		    u8 * data, int length, int restart)
>  {
>  	unsigned timeout = i2c->adap.timeout;
> -	int i;
> +	int i, ret;
>  	u32 flags = restart ? CCR_RSTA : 0;
>  
>  	/* Start with MEN */
> @@ -201,8 +212,9 @@ static int mpc_read(struct mpc_i2c *i2c,
>  	/* Write target address byte - this time with the read flag set */
>  	writeb((target << 1) | 1, i2c->base + MPC_I2C_DR);
>  
> -	if (i2c_wait(i2c, timeout, 1) < 0)
> -		return -1;
> +	ret = i2c_wait(i2c, timeout, 1);
> +	if (ret < 0)
> +		return ret;
>  
>  	if (length) {
>  		if (length == 1)
> @@ -214,8 +226,9 @@ static int mpc_read(struct mpc_i2c *i2c,
>  	}
>  
>  	for (i = 0; i < length; i++) {
> -		if (i2c_wait(i2c, timeout, 0) < 0)
> -			return -1;
> +		ret = i2c_wait(i2c, timeout, 0);
> +		if (ret < 0)
> +			return ret;
>  
>  		/* Generate txack on next to last byte */
>  		if (i == length - 2)
> @@ -246,8 +259,13 @@ static int mpc_xfer(struct i2c_adapter *
>  			return -EINTR;
>  		}
>  		if (time_after(jiffies, orig_jiffies + HZ)) {
> -			pr_debug("I2C: timeout\n");
> -			return -EIO;
> +			writeccr(i2c, 0);
> +
> +			/* try one more time before we error */
> +			if (readb(i2c->base + MPC_I2C_SR) & CSR_MBB) {
> +				pr_debug("I2C: timeout\n");
> +				return -EIO;
> +			}
>  		}
>  		schedule();
>  	}
> @@ -325,6 +343,7 @@ static int fsl_i2c_probe(struct platform
>  			goto fail_irq;
>  		}
>  
> +	writeccr(i2c, 0);
>  	mpc_i2c_setclock(i2c);
>  	platform_set_drvdata(pdev, i2c);

-- 
Jean Delvare