Re: [PATCH v2 2/6] i2c: at91: implement i2c bus recovery

[Codrin.Ciubotariu]

On 09.01.2020 09:48, Ludovic Desroches wrote:
> On Fri, Jan 03, 2020 at 09:49:07AM +0000, Codrin Ciubotariu - M19940 wrote:
>> From: Kamel Bouhara <kamel.bouhara@xxxxxxxxxxx>
>>
>> Implement i2c bus recovery when slaves devices might hold SDA low.
>> In this case re-assign SCL/SDA to gpios and issue 9 dummy clock pulses
>> until the slave release SDA.
>>
>> Signed-off-by: Kamel Bouhara <kamel.bouhara@xxxxxxxxxxx>
>> [codrin.ciubotariu@xxxxxxxxxxxxx: release gpios on error; move i2c_recover_bus]
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
>> ---
>>
>> 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-master.c | 79 ++++++++++++++++++++++++++++
>>   drivers/i2c/busses/i2c-at91.h        |  8 +++
>>   2 files changed, 87 insertions(+)
>>
>> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
>> index 7a862e00b475..c55e8ff35201 100644
>> --- a/drivers/i2c/busses/i2c-at91-master.c
>> +++ b/drivers/i2c/busses/i2c-at91-master.c
>> @@ -18,11 +18,13 @@
>>   #include <linux/dma-mapping.h>
>>   #include <linux/dmaengine.h>
>>   #include <linux/err.h>
>> +#include <linux/gpio/consumer.h>
>>   #include <linux/i2c.h>
>>   #include <linux/interrupt.h>
>>   #include <linux/io.h>
>>   #include <linux/of.h>
>>   #include <linux/of_device.h>
>> +#include <linux/pinctrl/consumer.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/platform_data/dma-atmel.h>
>>   #include <linux/pm_runtime.h>
>> @@ -478,6 +480,7 @@ 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
>> @@ -637,6 +640,13 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
>>   		at91_twi_write(dev, AT91_TWI_CR,
>>   			       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);
>> +	}
>> +
>>   	return ret;
>>   }
>>   
>> @@ -806,6 +816,71 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
>>   	return ret;
>>   }
>>   
>> +static void at91_prepare_twi_recovery(struct i2c_adapter *adap)
>> +{
>> +	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
>> +
>> +	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_gpio);
>> +}
>> +
>> +static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
>> +{
>> +	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
>> +
>> +	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
>> +}
>> +
>> +static int at91_init_twi_recovery_info(struct platform_device *pdev,
>> +				       struct at91_twi_dev *dev)
>> +{
>> +	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> +
>> +	dev->pinctrl = devm_pinctrl_get(&pdev->dev);
>> +	if (!dev->pinctrl || IS_ERR(dev->pinctrl)) {
>> +		dev_info(dev->dev, "can't get pinctrl, bus recovery not supported\n");
>> +		return PTR_ERR(dev->pinctrl);
>> +	}
>> +
>> +	dev->pinctrl_pins_default = pinctrl_lookup_state(dev->pinctrl,
>> +							 PINCTRL_STATE_DEFAULT);
>> +	dev->pinctrl_pins_gpio = pinctrl_lookup_state(dev->pinctrl,
>> +						      "gpio");
>> +	rinfo->sda_gpiod = devm_gpiod_get(&pdev->dev, "sda", GPIOD_IN);
>> +	if (PTR_ERR(rinfo->sda_gpiod) == -EPROBE_DEFER)
>> +		return -EPROBE_DEFER;
>> +
>> +	rinfo->scl_gpiod = devm_gpiod_get(&pdev->dev, "scl",
>> +					  GPIOD_OUT_HIGH_OPEN_DRAIN);
>> +	if (PTR_ERR(rinfo->scl_gpiod) == -EPROBE_DEFER)
>> +		return -EPROBE_DEFER;
>> +
>> +	if (IS_ERR(rinfo->sda_gpiod) ||
>> +	    IS_ERR(rinfo->scl_gpiod) ||
>> +	    IS_ERR(dev->pinctrl_pins_default) ||
>> +	    IS_ERR(dev->pinctrl_pins_gpio)) {
>> +		dev_info(&pdev->dev, "recovery information incomplete\n");
>> +		if (!IS_ERR(rinfo->sda_gpiod)) {
>> +			gpiod_put(rinfo->sda_gpiod);
>> +			rinfo->sda_gpiod = NULL;
>> +		}
>> +		if (!IS_ERR(rinfo->scl_gpiod)) {
>> +			gpiod_put(rinfo->scl_gpiod);
>> +			rinfo->scl_gpiod = NULL;
>> +		}
>> +		return -EINVAL;
>> +	}
>> +
>> +	dev_info(&pdev->dev, "using scl%s for recovery\n",
>> +		 rinfo->sda_gpiod ? ",sda" : "");
> 
> Is it possible to have scl without sda? From the condition before, if
> there is an error for sda or scl, an error is returned.

No, it's not. We need both sda and scl gpios. I will fix it.

> 
>> +
>> +	rinfo->prepare_recovery = at91_prepare_twi_recovery;
>> +	rinfo->unprepare_recovery = at91_unprepare_twi_recovery;
>> +	rinfo->recover_bus = i2c_generic_scl_recovery;
>> +	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)
>>   {
>> @@ -838,6 +913,10 @@ int at91_twi_probe_master(struct platform_device *pdev,
>>   						     "i2c-analog-filter");
>>   	at91_calc_twi_clock(dev);
>>   
>> +	rc = at91_init_twi_recovery_info(pdev, dev);
>> +	if (rc == -EPROBE_DEFER)
>> +		return rc;
>> +
>>   	dev->adapter.algo = &at91_twi_algorithm;
>>   	dev->adapter.quirks = &at91_twi_quirks;
>>   
>> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
>> index 977a67bc0f88..eb335b71e775 100644
>> --- a/drivers/i2c/busses/i2c-at91.h
>> +++ b/drivers/i2c/busses/i2c-at91.h
>> @@ -151,6 +151,10 @@ struct at91_twi_dev {
>>   	u32 fifo_size;
>>   	struct at91_twi_dma dma;
>>   	bool slave_detected;
>> +	struct i2c_bus_recovery_info rinfo;
>> +	struct pinctrl *pinctrl;
>> +	struct pinctrl_state *pinctrl_pins_default;
>> +	struct pinctrl_state *pinctrl_pins_gpio;
>>   #ifdef CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL
>>   	unsigned smr;
>>   	struct i2c_client *slave;
>> @@ -171,6 +175,10 @@ void at91_init_twi_bus_master(struct at91_twi_dev *dev);
>>   int at91_twi_probe_master(struct platform_device *pdev, u32 phy_addr,
>>   			  struct at91_twi_dev *dev);
>>   
> 
> Wrong names here:
> 
>> +void at91_twi_prepare_recovery(struct i2c_adapter *adap);
> at91_prepare_twi_recovery
> 
>> +void at91_twi_unprepare_recovery(struct i2c_adapter *adap);
> at91_unprepare_twi_recovery
> 
>> +void at91_twi_init_recovery_info(struct at91_twi_dev *dev);
> at91_init_twi_recovery_info
> 
> Are these declarations still needed?

No, there is not. They are used only in the master mode of the driver. I 
will remove them.

Thank you for your review Ludovic.

Best regards,
Codrin