Re: [PATCH 8/9] i2c: qcom-cci: add support of optional vbus-supply regulators

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 03 Feb 08:47 PST 2022, Vladimir Zapolskiy wrote:

> The change adds handling of optional vbus regulators in the driver.
> 
> Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
> ---
>  drivers/i2c/busses/i2c-qcom-cci.c | 49 +++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
> index 775945f7b4cd..2fc7f1f2616f 100644
> --- a/drivers/i2c/busses/i2c-qcom-cci.c
> +++ b/drivers/i2c/busses/i2c-qcom-cci.c
> @@ -11,6 +11,7 @@
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regulator/consumer.h>
>  
>  #define CCI_HW_VERSION				0x0
>  #define CCI_RESET_CMD				0x004
> @@ -480,6 +481,20 @@ static void cci_disable_clocks(struct cci *cci)
>  static int __maybe_unused cci_suspend_runtime(struct device *dev)
>  {
>  	struct cci *cci = dev_get_drvdata(dev);
> +	struct regulator *bus_regulator;
> +	unsigned int i;
> +
> +	for (i = 0; i < cci->data->num_masters; i++) {
> +		if (!cci->master[i].cci)
> +			continue;
> +
> +		bus_regulator = cci->master[i].adap.bus_regulator;
> +		if (!bus_regulator)
> +			continue;
> +
> +		if (regulator_is_enabled(bus_regulator) > 0)
> +			regulator_disable(bus_regulator);
> +	}
>  
>  	cci_disable_clocks(cci);
>  	return 0;
> @@ -488,12 +503,30 @@ static int __maybe_unused cci_suspend_runtime(struct device *dev)
>  static int __maybe_unused cci_resume_runtime(struct device *dev)
>  {
>  	struct cci *cci = dev_get_drvdata(dev);
> +	struct regulator *bus_regulator;
> +	unsigned int i;
>  	int ret;
>  
>  	ret = cci_enable_clocks(cci);
>  	if (ret)
>  		return ret;
>  
> +	for (i = 0; i < cci->data->num_masters; i++) {
> +		if (!cci->master[i].cci)
> +			continue;
> +
> +		bus_regulator = cci->master[i].adap.bus_regulator;
> +		if (!bus_regulator)
> +			continue;
> +
> +		if (!regulator_is_enabled(bus_regulator)) {

regulator_is_enabled() tests if the regulator is enabled, not if you
have enabled it. So if this is a shared regulator you might learn that
it's already on, skip your regulator_enable() and then the other
consumer turns it off behind your back.

If you want the regulator to be on, you should regulator_enable().

> +			ret = regulator_enable(bus_regulator);
> +			if (ret)
> +				dev_err(dev, "failed to enable regulator: %d\n",
> +					ret);
> +		}
> +	}
> +
>  	cci_init(cci);
>  	return 0;
>  }
> @@ -593,6 +626,7 @@ static int cci_probe(struct platform_device *pdev)
>  	dev_dbg(dev, "CCI HW version = 0x%08x", val);
>  
>  	for_each_available_child_of_node(dev->of_node, child) {
> +		struct regulator *bus_regulator;
>  		struct cci_master *master;
>  		u32 idx;
>  
> @@ -637,6 +671,21 @@ static int cci_probe(struct platform_device *pdev)
>  			master->cci = NULL;
>  			goto error_i2c;
>  		}
> +
> +		/*
> +		 * It might be possible to find an optional vbus supply, but
> +		 * it requires to pass the registration of an I2C adapter
> +		 * device and its association with a bus device tree node.
> +		 */

I'm afraid that I don't understand this comment. The regulator is
optional because most of the time we don't control it explicitly.

So a comment like "Control of IO supply is optional" seems more
relevant.

Regards,
Bjorn

> +		bus_regulator = devm_regulator_get_optional(&master->adap.dev,
> +							    "vbus");
> +		if (IS_ERR(bus_regulator)) {
> +			ret = PTR_ERR(bus_regulator);
> +			if (ret == -EPROBE_DEFER)
> +				goto error_i2c;
> +			bus_regulator = NULL;
> +		}
> +		master->adap.bus_regulator = bus_regulator;
>  	}
>  
>  	ret = cci_reset(cci);
> -- 
> 2.33.0
>