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SubjectRe: [PATCH v2 3/4] i2c: omap: don't reset controller if Arbitration Lost detected
On Sat, Nov 22, 2014 at 02:51:47AM +0400, Alexander Kochetkov wrote:
> Arbitration Lost is an expected situation in a multimaster
> environment. I2C controller (IP) correctly detect and report AL.
>
> The only one visible reason for reseting IP in the AL case is
> to avoid advisory 1.94 (omap3) and errata i595 (omap4): "I2C:
> After an Arbitration is Lost the Module Incorrectly Starts
> the Next Transfer".
>
> Errata workaround states: "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 set MST and STT bits
> separately and doesn't create condition for errata. So the reset
> is not necessary.
>
> Also corrected return value for AL to -EAGAIN.
>
> Tested on Beagleboard XM C.
>
> Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>

you could have kept my tested-by and reviewed-by:

Tested-by: Felipe Balbi <balbi@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>


> On 21.10.2014 21:11, Wolfram Sang <wsa@the-dreams.de> wrote:
> > The errno for AL is -EAGAIN. Curly braces are not needed.
>
> Thank you, Wolfram, fixed.
>
> drivers/i2c/busses/i2c-omap.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 3ffb9c0..02da567 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -707,13 +707,15 @@ 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 |
> - OMAP_I2C_STAT_XUDF)) {
> + 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 -EAGAIN;
> +
> if (dev->cmd_err & OMAP_I2C_STAT_NACK) {
> if (msg->flags & I2C_M_IGNORE_NAK)
> return 0;
> --
> 1.7.9.5
>

--
balbi
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