Re: [PATCH, v2] Let PCA9564 recover from unacked data byte (state 0x30)

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

[-- Attachment #1: Type: text/plain, Size: 2655 bytes --]

Hi Enrik,

one minor nit. If that is sorted out, you can add

Reviewed-by: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

Thanks for the patch,

   Wolfram

On Thu, Apr 09, 2009 at 11:38:55AM +0200, Enrik Berkhan wrote:
> Currently, the i2c-algo-pca driver does nothing if the chip enters state
> 0x30 (Data byte in I2CDAT has been transmitted; NOT ACK has been
> received).  Thus, the i2c bus connected to the controller gets stuck
> afterwards.
> 
> I have seen this kind of error on a custom board in certain load
> situations most probably caused by interference or noise.
> 
> A possible reaction is to let the controller generate a STOP condition.
> This is documented in the controller data sheet and the same is done for
> other NACK states as well.
> 
> Further, state 0x38 isn't handled completely, either. Try to do another
> START in this case like the manual says. As this couldn't be tested,
> I've added a comment to try to reset the chip if the START doesn't help
> as suggested by Wolfram Sang.
> 
> Signed-off-by: Enrik Berkhan <Enrik.Berkhan-JJi787mZWgc@public.gmane.org>
> ---
>  drivers/i2c/algos/i2c-algo-pca.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> Index: drivers/i2c/algos/i2c-algo-pca.c
> ===================================================================
> --- drivers/i2c/algos/i2c-algo-pca.c.orig	2009-04-07 11:23:08.000000000 +0200
> +++ drivers/i2c/algos/i2c-algo-pca.c	2009-04-09 11:10:11.000000000 +0200
> @@ -270,10 +270,17 @@ static int pca_xfer(struct i2c_adapter *
>  
>  		case 0x30: /* Data byte in I2CDAT has been transmitted; NOT ACK has been received */
>  			DEB2("NOT ACK received after data byte\n");
> +			pca_stop(adap);
>  			goto out;
>  
>  		case 0x38: /* Arbitration lost during SLA+W, SLA+R or data bytes */
>  			DEB2("Arbitration lost\n");
> +			/*
> +			 * The manual says to send another start
> +			 * condition in this case. If this won't be

A pointer, where the manual says it, is always helpful (revision, chapter, page
number or such).

> +			 * sufficient, try pca_reset() instead.
> +			 */
> +			pca_start(adap);
>  			goto out;
>  
>  		case 0x58: /* Data byte has been received; NOT ACK has been returned */
> --
> To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 197 bytes --]