Re: [PATCH v4 1/4] i2c: at91: Send bus clear command if SDA is down

[Codrin.Ciubotariu]

On 30.03.2020 00:13, Ludovic Desroches - M43218 wrote:
> On 2/25/2020 4:50 PM, Codrin Ciubotariu wrote:
>> After a transfer timeout, some faulty I2C slave devices might hold down
>> the SDA pin. We can generate a bus clear command, hoping that the slave
>> might release the pins.
>> If the CLEAR command is not supported, we will use gpio recovery, if
>> available, to reset the bus.
>>
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
> 
> Sounds good so
> Acked-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxxxxxx>
> 
> Wolfram, you have accepted the v3 of the recovery support and requested
> these changes. It has been sent as a v4, but, in fact, this patch goes
> on top on v3. It could, should, have been a new patch.
> 
> Regards
> 
> Ludovic

Hello, any updates on this patch? Do you want me to change anything?

Best regards,
Codrin

> 
>> ---
>>
>> Changes in v4:
>>    - moved the HW bus clear command in a recover_bus() function, to be able
>>      to just call i2c_recover_bus() if a transfer fails;
>>    - recovery gpios are no longer taken if HW bus clear command is
>>      supported;
>>
>> Changes in v3:
>>    - removed unnecessary condition from info print;
>>    - removed unneded declarations;
>>
>> Changes in v2:
>>    - called i2c_recover_bus() after an error occurs, if SDA is down;
>>    - release gpios if recovery information is incomplete;
>>
>>    drivers/i2c/busses/i2c-at91-core.c   |  2 ++
>>    drivers/i2c/busses/i2c-at91-master.c | 49 ++++++++++++++++++++++++----
>>    drivers/i2c/busses/i2c-at91.h        |  7 +++-
>>    3 files changed, 50 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
>> index 3da1a8acecb5..e14edd236108 100644
>> --- a/drivers/i2c/busses/i2c-at91-core.c
>> +++ b/drivers/i2c/busses/i2c-at91-core.c
>> @@ -131,6 +131,7 @@ static struct at91_twi_pdata sama5d2_config = {
>>    	.has_dig_filtr = true,
>>    	.has_adv_dig_filtr = true,
>>    	.has_ana_filtr = true,
>> +	.has_clear_cmd = false,	/* due to errata, CLEAR cmd is not working */
>>    };
>>    
>>    static struct at91_twi_pdata sam9x60_config = {
>> @@ -142,6 +143,7 @@ static struct at91_twi_pdata sam9x60_config = {
>>    	.has_dig_filtr = true,
>>    	.has_adv_dig_filtr = true,
>>    	.has_ana_filtr = true,
>> +	.has_clear_cmd = true,
>>    };
>>    
>>    static const struct of_device_id atmel_twi_dt_ids[] = {
>> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
>> index 0aba51a7df32..776e95962ab6 100644
>> --- a/drivers/i2c/busses/i2c-at91-master.c
>> +++ b/drivers/i2c/busses/i2c-at91-master.c
>> @@ -480,7 +480,6 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
>>    	unsigned long time_left;
>>    	bool has_unre_flag = dev->pdata->has_unre_flag;
>>    	bool has_alt_cmd = dev->pdata->has_alt_cmd;
>> -	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>>    
>>    	/*
>>    	 * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
>> @@ -641,11 +640,12 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
>>    			       AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
>>    	}
>>    
>> -	if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
>> -		dev_dbg(dev->dev,
>> -			"SDA is down; clear bus using gpio\n");
>> -		i2c_recover_bus(&dev->adapter);
>> -	}
>> +	/*
>> +	 * some faulty I2C slave devices might hold SDA down;
>> +	 * we can send a bus clear command, hoping that the pins will be
>> +	 * released
>> +	 */
>> +	i2c_recover_bus(&dev->adapter);
>>    
>>    	return ret;
>>    }
>> @@ -830,7 +830,7 @@ static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
>>    	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
>>    }
>>    
>> -static int at91_init_twi_recovery_info(struct platform_device *pdev,
>> +static int at91_init_twi_recovery_gpio(struct platform_device *pdev,
>>    				       struct at91_twi_dev *dev)
>>    {
>>    	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> @@ -880,6 +880,41 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
>>    	return 0;
>>    }
>>    
>> +static int at91_twi_recover_bus_cmd(struct i2c_adapter *adap)
>> +{
>> +	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
>> +
>> +	dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);
>> +	if (!(dev->transfer_status & AT91_TWI_SDA)) {
>> +		dev_dbg(dev->dev, "SDA is down; sending bus clear command\n");
>> +		if (dev->use_alt_cmd) {
>> +			unsigned int acr;
>> +
>> +			acr = at91_twi_read(dev, AT91_TWI_ACR);
>> +			acr &= ~AT91_TWI_ACR_DATAL_MASK;
>> +			at91_twi_write(dev, AT91_TWI_ACR, acr);
>> +		}
>> +		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int at91_init_twi_recovery_info(struct platform_device *pdev,
>> +				       struct at91_twi_dev *dev)
>> +{
>> +	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> +	bool has_clear_cmd = dev->pdata->has_clear_cmd;
>> +
>> +	if (!has_clear_cmd)
>> +		return at91_init_twi_recovery_gpio(pdev, dev);
>> +
>> +	rinfo->recover_bus = at91_twi_recover_bus_cmd;
>> +	dev->adapter.bus_recovery_info = rinfo;
>> +
>> +	return 0;
>> +}
>> +
>>    int at91_twi_probe_master(struct platform_device *pdev,
>>    			  u32 phy_addr, struct at91_twi_dev *dev)
>>    {
>> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
>> index f57a6cab96b4..7e7b4955ca7f 100644
>> --- a/drivers/i2c/busses/i2c-at91.h
>> +++ b/drivers/i2c/busses/i2c-at91.h
>> @@ -36,6 +36,7 @@
>>    #define	AT91_TWI_SVDIS		BIT(5)	/* Slave Transfer Disable */
>>    #define	AT91_TWI_QUICK		BIT(6)	/* SMBus quick command */
>>    #define	AT91_TWI_SWRST		BIT(7)	/* Software Reset */
>> +#define	AT91_TWI_CLEAR		BIT(15) /* Bus clear command */
>>    #define	AT91_TWI_ACMEN		BIT(16) /* Alternative Command Mode Enable */
>>    #define	AT91_TWI_ACMDIS		BIT(17) /* Alternative Command Mode Disable */
>>    #define	AT91_TWI_THRCLR		BIT(24) /* Transmit Holding Register Clear */
>> @@ -69,6 +70,8 @@
>>    #define	AT91_TWI_NACK		BIT(8)	/* Not Acknowledged */
>>    #define	AT91_TWI_EOSACC		BIT(11)	/* End Of Slave Access */
>>    #define	AT91_TWI_LOCK		BIT(23) /* TWI Lock due to Frame Errors */
>> +#define	AT91_TWI_SCL		BIT(24) /* TWI SCL status */
>> +#define	AT91_TWI_SDA		BIT(25) /* TWI SDA status */
>>    
>>    #define	AT91_TWI_INT_MASK \
>>    	(AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
>> @@ -81,7 +84,8 @@
>>    #define	AT91_TWI_THR		0x0034	/* Transmit Holding Register */
>>    
>>    #define	AT91_TWI_ACR		0x0040	/* Alternative Command Register */
>> -#define	AT91_TWI_ACR_DATAL(len)	((len) & 0xff)
>> +#define	AT91_TWI_ACR_DATAL_MASK	GENMASK(15, 0)
>> +#define	AT91_TWI_ACR_DATAL(len)	((len) & AT91_TWI_ACR_DATAL_MASK)
>>    #define	AT91_TWI_ACR_DIR	BIT(8)
>>    
>>    #define AT91_TWI_FILTR		0x0044
>> @@ -118,6 +122,7 @@ struct at91_twi_pdata {
>>    	bool has_dig_filtr;
>>    	bool has_adv_dig_filtr;
>>    	bool has_ana_filtr;
>> +	bool has_clear_cmd;
>>    	struct at_dma_slave dma_slave;
>>    };
>>    
>>
>