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SubjectRe: [PATCH 3/4] i2c: omap: don't reset controller if Arbitration Lost detected
On Fri, Nov 21, 2014 at 01:28:44AM +0400, Alexander Kochetkov wrote:
> Arbitration Lost is a expected situation in a multimaster environment.
> IP correctly detect it.
>
> The only reason for reseting IP in the AL case is to be sure to
> avoid advisory 1.94 (omap3) and errata i595 (omap4):
> "I2C: After an Arbitration is Lost the Module Incorrectly Starts
> the Next Transfer" with workaround: "The MST and STT bits inside
> I2C_CON should be set to 1 at the same moment (avoid setting the
> MST bit to 1 while STT = 0)."
>
> The driver never writes MST and STT bits separately and doesn't
> create condition for errata. So the reset is not necessary.
>
> Tested on Beagleboard XM C.
>
> Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
> ---
> drivers/i2c/busses/i2c-omap.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 3ffb9c0..47103e7 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -707,13 +707,17 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
> return 0;
>
> /* We have an error */
> - if (dev->cmd_err & (OMAP_I2C_STAT_AL | OMAP_I2C_STAT_ROVR |
> + if (dev->cmd_err & (OMAP_I2C_STAT_ROVR |
> OMAP_I2C_STAT_XUDF)) {
> omap_i2c_reset(dev);
> __omap_i2c_init(dev);
> return -EIO;
> }
>
> + if (dev->cmd_err & OMAP_I2C_STAT_AL) {
> + return -EIO;
> + }

The errno for AL is -EAGAIN. Curly braces are not needed.

> +
> if (dev->cmd_err & OMAP_I2C_STAT_NACK) {
> if (msg->flags & I2C_M_IGNORE_NAK)
> return 0;
> --
> 1.7.9.5
>
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