Re: [PATCH] i2c-mpc: generate START condition after STOP caused by read i2c_msg

[Wolfram Sang <w.sang@pengutronix.de>]

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On Thu, May 14, 2009 at 10:10:03AM +0200, Esben Haabendal wrote:
> This fixes MAL (arbitration lost) bug caused by illegal use of
> RSTA (repeated START) after STOP condition generated after last byte
> of reads.
>

Could you elaborate a bit, please? Like an example when the original bug
occured (so I could reproduce easily) and how this patch actually solves
the problem.


> Signed-off-by: Esben Haabendal <eha@doredevelopment.dk>
> ---
>  drivers/i2c/busses/i2c-mpc.c |    9 +++++++--
>  1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
> index 4af5c09..9fe05d9 100644
> --- a/drivers/i2c/busses/i2c-mpc.c
> +++ b/drivers/i2c/busses/i2c-mpc.c
> @@ -456,17 +456,22 @@ static int mpc_xfer(struct i2c_adapter *adap,  
> struct i2c_msg *msgs, int num)
>  	}
>
>  	for (i = 0; ret >= 0 && i < num; i++) {
> +		int restart = i;
>  		pmsg = &msgs[i];
>  		dev_dbg(i2c->dev,
>  			"Doing %s %d bytes to 0x%02x - %d of %d messages\n",
>  			pmsg->flags & I2C_M_RD ? "read" : "write",
>  			pmsg->len, pmsg->addr, i + 1, num);
> +		if (i > 0 && ((pmsg-1)->flags & I2C_M_RD))

CodingStyle: Spaces around '-'

> +			restart = 0;
>  		if (pmsg->flags & I2C_M_RD)
>  			ret =
> -			    mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, i);
> +			    mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len,
> +				     restart);
>  		else
>  			ret =
> -			    mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i);
> +			    mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len,
> +				      restart);
>  	}
>  	mpc_i2c_stop(i2c);
>  	return (ret < 0) ? ret : num;
> -- 
> 1.6.0.4
>
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-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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