linux-kernel - Re: [RESEND][PATCH] i2c: imx: add support for I2C_M

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Date:   Fri, 5 Jul 2019 20:38:48 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Mans Rullgard <mans@...sr.com>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de, Aisheng Dong <aisheng.dong@....com>,
        Shawn Guo <shawnguo@...nel.org>
Subject: Re: [RESEND][PATCH] i2c: imx: add support for I2C_M_STOP flag

On Wed, Jul 03, 2019 at 05:47:32PM +0100, Mans Rullgard wrote:
> Add support for the I2C_M_STOP flag to the i2c-imx driver.  This allows
> devices requiring a stop between messages to work with this controller.
> 
> Signed-off-by: Mans Rullgard <mans@...sr.com>

The problem with this driver is that it is unmaintained, sadly :( I'll
cc some people who might be interested...

> ---
>  drivers/i2c/busses/i2c-imx.c | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 7bd409eaf0ac..a7f801bb5dc9 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -908,10 +908,17 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  
>  	/* read/write data */
>  	for (i = 0; i < num; i++) {
> -		if (i == num - 1)
> -			is_lastmsg = true;
> +		if (is_lastmsg) {
> +			/* previous message had I2C_M_STOP flag set */
> +			temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> +			temp |= I2CR_MSTA;
> +			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> +			result = i2c_imx_bus_busy(i2c_imx, 1);
> +			if (result)
> +				goto fail0;
> +		}
>  
> -		if (i) {
> +		if (i && !is_lastmsg) {
>  			dev_dbg(&i2c_imx->adapter.dev,
>  				"<%s> repeated start\n", __func__);
>  			temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> @@ -921,6 +928,10 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  			if (result)
>  				goto fail0;
>  		}
> +
> +		if (i == num - 1 || (msgs[i].flags & I2C_M_STOP))
> +			is_lastmsg = true;
> +
>  		dev_dbg(&i2c_imx->adapter.dev,
>  			"<%s> transfer message: %d\n", __func__, i);
>  		/* write/read data */
> @@ -948,6 +959,13 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  				result = i2c_imx_dma_write(i2c_imx, &msgs[i]);
>  			else
>  				result = i2c_imx_write(i2c_imx, &msgs[i]);
> +
> +			if (msgs[i].flags & I2C_M_STOP) {
> +				temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> +				temp &= ~I2CR_MSTA;
> +				imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> +				i2c_imx_bus_busy(i2c_imx, 0);
> +			}
>  		}
>  		if (result)
>  			goto fail0;
> @@ -1034,7 +1052,7 @@ static int i2c_imx_init_recovery_info(struct imx_i2c_struct *i2c_imx,
>  
>  static u32 i2c_imx_func(struct i2c_adapter *adapter)
>  {
> -	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
> +	return I2C_FUNC_I2C | I2C_FUNC_PROTOCOL_MANGLING | I2C_FUNC_SMBUS_EMUL
>  		| I2C_FUNC_SMBUS_READ_BLOCK_DATA;
>  }
>  
> -- 
> 2.22.0
> 

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