[PATCH] i2c: imx: Add arbitration lost check

[PATCH] i2c: imx: Add arbitration lost check

[Haibo Chen]

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-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
---
 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..144b620 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 -EIO;
+		}
+
 		if (for_busy && (temp & I2SR_IBB))
 			break;
 		if (!for_busy && !(temp & I2SR_IBB))
-- 
1.9.1

RE: [PATCH] i2c: imx: Add arbitration lost check

[fugang.duan-KZfg59tc24xl57MIdRCFDg]

From: Haibo Chen <haibo.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org> Sent: Monday, September 01, 2014 4:59 PM
>To: wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org
>Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Duan Fugang-B38611
>Subject: [PATCH] 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-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
>---
> 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..144b620 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 -EIO;
>+		}
>+
> 		if (for_busy && (temp & I2SR_IBB))
> 			break;
> 		if (!for_busy && !(temp & I2SR_IBB))
>--
>1.9.1

Acked-by: Fugang Duan <B38611-KZfg59tc24xl57MIdRCFDg@public.gmane.org>

Thanks,
Andy

Re: [PATCH] i2c: imx: Add arbitration lost check

[Wolfram Sang]

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> --- 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 **/

One '*' is enough on each side.

> +		if (temp & I2SR_IAL) {
> +			temp &= ~I2SR_IAL;
> +			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
> +			return -EIO;

Documentation/i2c/fault-codes defines 'EAGAIN' for arbitration lost.

> +		}
> +
>  		if (for_busy && (temp & I2SR_IBB))
>  			break;
>  		if (!for_busy && !(temp & I2SR_IBB))
> -- 
> 1.9.1
> 

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