linux-kernel - Re: [PATCH v2 6/6] i2c: i2c-stm32f7: Implement I2C recovery mechanism

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Date:   Sat, 24 Mar 2018 23:56:30 +0100
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Cc:     Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] i2c: i2c-stm32f7: Implement I2C recovery mechanism

On Wed, Mar 21, 2018 at 05:49:00PM +0100, Pierre-Yves MORDRET wrote:
> Feature prevents I2C lock-ups. Mechanism resets I2C state machine
> and releases SCL/SDA signals but preserves I2C registers.
> 
> Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@...com>
> ---
>   Version history:
>     v1:
>        * Initial
>     v2:
>        * Don't use i2c engine recovery mechanism since driver
>          procedure only recover master and not the slave.

s/recovery/release/ throughout the patch, please. Recovery is really
something else. Also, I think the dev_info's are too noisy in the log
files. I'd think the whole driver could be lifted from quite some
logging...

> ---
> ---
>  drivers/i2c/busses/i2c-stm32f7.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index 91f73e0..9a9c469 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -718,6 +718,20 @@ static void stm32f7_i2c_smbus_reload(struct stm32f7_i2c_dev *i2c_dev)
>  	writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
>  }
>  
> +static int stm32f7_i2c_recover_bus(struct i2c_adapter *i2c_adap)
> +{
> +	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
> +
> +	dev_info(i2c_dev->dev, "Trying to recover bus\n");
> +
> +	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
> +			     STM32F7_I2C_CR1_PE);
> +
> +	stm32f7_i2c_hw_config(i2c_dev);
> +
> +	return 0;
> +}
> +
>  static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
>  {
>  	u32 status;
> @@ -727,12 +741,18 @@ static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
>  					 status,
>  					 !(status & STM32F7_I2C_ISR_BUSY),
>  					 10, 1000);
> +	if (!ret)
> +		return 0;
> +
> +	dev_info(i2c_dev->dev, "bus busy\n");
> +
> +	ret = stm32f7_i2c_recover_bus(&i2c_dev->adap);
>  	if (ret) {
> -		dev_dbg(i2c_dev->dev, "bus busy\n");
> -		ret = -EBUSY;
> +		dev_err(i2c_dev->dev, "Failed to recover the bus (%d)\n", ret);
> +		return ret;
>  	}
>  
> -	return ret;
> +	return -EBUSY;
>  }
>  
>  static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
> @@ -1474,6 +1494,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
>  	if (status & STM32F7_I2C_ISR_BERR) {
>  		dev_err(dev, "<%s>: Bus error\n", __func__);
>  		writel_relaxed(STM32F7_I2C_ICR_BERRCF, base + STM32F7_I2C_ICR);
> +		stm32f7_i2c_recover_bus(&i2c_dev->adap);
>  		f7_msg->result = -EIO;
>  	}
>  
> -- 
> 2.7.4
> 

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