[PATCHv3,1/2] i2c: designware: introduce a custom scl recovery for SoCFPGA platforms

The I2C pins on the SoCFPGA platforms do not go through a GPIO module,
thus cannot be recovered by the default method of by doing a GPIO access.
Only a reset of the I2C IP block can a recovery be successful.

The assignment of the recover_bus needs to get done before the call to
devm_gpiod_get_optional(), otherwise, the assignment is not taking place
because of an error after returning from devm_gpiod_get_optional().

Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
---
v3: simplify the function
    update commit message
v2: remove change to MODEL_MASK
    s/i2c_custom_scl_recovery/i2c_socfpga_scl_recovery
---
 drivers/i2c/busses/i2c-designware-core.h    |  1 +
 drivers/i2c/busses/i2c-designware-master.c  | 12 ++++++++++++
 drivers/i2c/busses/i2c-designware-platdrv.c |  1 +
 3 files changed, 14 insertions(+)

On Mon, Jun 13, 2022 at 04:00:31PM -0500, Dinh Nguyen wrote:
> The I2C pins on the SoCFPGA platforms do not go through a GPIO module,
> thus cannot be recovered by the default method of by doing a GPIO access.
> Only a reset of the I2C IP block can a recovery be successful.
> 
> The assignment of the recover_bus needs to get done before the call to
> devm_gpiod_get_optional(), otherwise, the assignment is not taking place
> because of an error after returning from devm_gpiod_get_optional().

Thanks for an update!
My comments below.

...

> +static int i2c_socfpga_scl_recovery(struct i2c_adapter *adap)
> +{
> +	i2c_dw_prepare_recovery(adap);
> +	i2c_dw_unprepare_recovery(adap);

Can we use

	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;

	bri->prepare_recovery(adap);
	bri->unprepare_recovery(adap);

> +	return 0;
> +}

instead and...

...

>  static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
>  {
>  	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>  	struct i2c_adapter *adap = &dev->adapter;
>  	struct gpio_desc *gpio;
>  
> +	if ((dev->flags & MODEL_MASK) == MODEL_SOCFPGA) {
> +		rinfo->recover_bus = i2c_socfpga_scl_recovery;
> +		adap->bus_recovery_info = rinfo;
> +	}
> +
>  	gpio = devm_gpiod_get_optional(dev->dev, "scl", GPIOD_OUT_HIGH);
>  	if (IS_ERR_OR_NULL(gpio))
>  		return PTR_ERR_OR_ZERO(gpio);

...this one to be transformed like (in a preparatory patch and in this one):

static int i2c_dw_init_socfpga_recovery_info(struct dw_i2c_dev *dev,
					     struct i2c_bus_recovery_info *rinfo)
{
	rinfo->recover_bus = i2c_socfpga_scl_recovery;
	return 0;
}

static int i2c_dw_init_generic_recovery_info(struct dw_i2c_dev *dev,
					     struct i2c_bus_recovery_info *rinfo)
{
	struct i2c_adapter *adap = &dev->adapter;
	struct gpio_desc *gpio;

	gpio = devm_gpiod_get_optional(dev->dev, "scl", GPIOD_OUT_HIGH);
	if (IS_ERR_OR_NULL(gpio))
		return PTR_ERR_OR_ZERO(gpio);

	rinfo->scl_gpiod = gpio;

	gpio = devm_gpiod_get_optional(dev->dev, "sda", GPIOD_IN);
	if (IS_ERR(gpio))
		return PTR_ERR(gpio);
	rinfo->sda_gpiod = gpio;

	rinfo->recover_bus = i2c_generic_scl_recovery;

	dev_info(dev->dev, "running with gpio recovery mode! scl%s",
		 rinfo->sda_gpiod ? ",sda" : "");

	return 0;
}

static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
{
	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
	struct i2c_adapter *adap = &dev->adapter;
	int ret;

	switch (dev->flags & MODEL_MASK) {
	case MODEL_SOCFPGA:
		ret = i2c_dw_init_socfpga_recovery_info(dev, rinfo);
		break;
	default:
		ret = i2c_dw_init_generic_recovery_info(dev, rinfo);
		break;
	}
	if (ret)
		return ret;

	rinfo->prepare_recovery = i2c_dw_prepare_recovery;
	rinfo->unprepare_recovery = i2c_dw_unprepare_recovery;
	adap->bus_recovery_info = rinfo;

	return 0;
}