Hi, Wolfram,
From: Haibo Chen <haibo.chen@xxxxxxxxxxxxx> Sent: Wednesday, September 03, 2014 1:52 PM + 0800
> To: wsa@xxxxxxxxxxxxx
> Cc: Duan Fugang-B38611; linux-i2c@xxxxxxxxxxxxxxx
> Subject: [PATCH v2] i2c: imx: Add arbitration lost check
>
> According to the i.mx spec, for multimaster mode, if I2C is enabled when
> the bus is busy and asserts start, hardware inhibits the transmission,
> clears MSTA without signaling a stop, generate an interrupt, and set
> I2C_I2SR[IAL] to indicate a failed attempt to engage the bus, which means
> arbitration lost. In this case, we should first test I2C_I2SR[IAL], and
> clear this bit if it is set, and then I2C controller default to slave
> receive mode.
>
> This patch check the IAL bit every time before an I2c transmission.
> if IAL is set, clear it and make I2C controller to default mode.
>
> Signed-off-by: Haibo Chen <haibo.chen@xxxxxxxxxxxxx>
> Acked-by: Fugang Duan <B38611@xxxxxxxxxxxxx>
> ---
> Changes for V2:
> -Use 'EAGAIN' instead of 'EIO' for arbitration lost -Modify the comment
> style
>
> drivers/i2c/busses/i2c-imx.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 613069b..ceff87c 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -268,6 +268,14 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct
> *i2c_imx, int for_busy)
>
> while (1) {
> temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> +
> + /* check for arbitration lost */
> + if (temp & I2SR_IAL) {
> + temp &= ~I2SR_IAL;
> + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
> + return -EAGAIN;
> + }
> +
> if (for_busy && (temp & I2SR_IBB))
> break;
> if (!for_busy && !(temp & I2SR_IBB))
> --
> 1.9.1
>
> --
Can you apply the patch or other comments ?
Thanks,
Haibo
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