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

Codrin.Ciubotariu
2020-01-09T10:54:44Z

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@bootlin.com>
>>
>> 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@bootlin.com>
>> [codrin.ciubotariu@microchip.com: release gpios on error; move i2c_recover_bus]
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
>> ---
>>
>> 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