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Subject: Re: [RESEND PATCH v1 6/6] i2c: i2c-stm32f7: Implement I2C recovery
 mechanism
To:     Phil Reid <preid@electromag.com.au>,
        Wolfram Sang <wsa@the-dreams.de>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        <linux-i2c@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <1520852023-27083-1-git-send-email-pierre-yves.mordret@st.com>
 <1520852023-27083-7-git-send-email-pierre-yves.mordret@st.com>
 <c9b7a9c9-4924-cadc-c539-0775aab23368@electromag.com.au>
From:   Pierre Yves MORDRET <pierre-yves.mordret@st.com>
Message-ID: <ceeba3e9-7912-c47a-02e2-f22cdaef5041@st.com>
Date:   Mon, 19 Mar 2018 17:25:20 +0100
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On 03/19/2018 10:36 AM, Phil Reid wrote:
> On 12/03/2018 18:53, 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@st.com>
>> ---
>>    Version history:
>>      v1:
>>         * Initial
>> ---
>> ---
>>   drivers/i2c/busses/i2c-stm32f7.c | 32 +++++++++++++++++++++++++++++---
>>   1 file changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
>> index 69a2e5e..3808bc9 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);
> 
> This only "releases" the scl / sda on the stm32f7 end (outputs are hiz I guess).
> It doesn't trigger the scl clocking needed to recover a stuck device  via i2c recovery
> from what I can see in the data sheet.
> 

Correct. This mechanism resets the core IP and not the slave.

> 
>> +
>> +	stm32f7_i2c_hw_config(i2c_dev);
> 
> Nothing in here either I think.
> 
> 
>> +
>> +	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 = 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,
>> @@ -1476,6 +1496,7 @@ 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);
>> +		i2c_recover_bus(&i2c_dev->adap);
>>   		f7_msg->result = -EIO;
>>   	}
>>   
>> @@ -1760,6 +1781,10 @@ static struct i2c_algorithm stm32f7_i2c_algo = {
>>   	.unreg_slave = stm32f7_i2c_unreg_slave,
>>   };
>>   
>> +static struct i2c_bus_recovery_info stm32f7_i2c_recovery_info = {
>> +	.recover_bus = stm32f7_i2c_recover_bus,
>> +};
>> +
>>   static int stm32f7_i2c_probe(struct platform_device *pdev)
>>   {
>>   	struct device_node *np = pdev->dev.of_node;
>> @@ -1879,6 +1904,7 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
>>   	adap->algo = &stm32f7_i2c_algo;
>>   	adap->dev.parent = &pdev->dev;
>>   	adap->dev.of_node = pdev->dev.of_node;
>> +	adap->bus_recovery_info = &stm32f7_i2c_recovery_info;
>>   
>>   	init_completion(&i2c_dev->complete);
>>   
>>
> 
>