Re: [PATCH v7 08/24] mfd: max77686: Add Dynamic Voltage Scaling (DVS) support

[Lee Jones]

I'd really like Linus Walleij to look over this if possible.

On Fri, 04 Jul 2014, Javier Martinez Canillas wrote:
> Some regulators on the MAX77686 PMIC have Dynamic Voltage Scaling
> (DVS) support that allows output voltage to change dynamically.
> 
> For MAX77686, these regulators are Buck regulators 2, 3 and 4.
> 
> Each Buck output voltage is selected using a set of external
> inputs: DVS1-3 and SELB2-4.
> 
> DVS registers can be used to configure the output voltages for each
> Buck regulator and which one is active is controled by DVSx lines.
> 
> SELBx lines are used to control if individual Buck lines are ON or OFF.
> 
> This patch adds support to configure the DVSx and SELBx lines
> from DT and to setup and read the GPIO lines connected to them.
> 
> Signed-off-by: Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
> ---
> 
> Changes since v6:
>  - Add a comment that max77686_read_gpios() function can sleep.
>    Sugggested by Krzysztof Kozlowski
> ---
>  drivers/mfd/max77686.c       | 119 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/max77686.h |  18 ++++---
>  2 files changed, 129 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mfd/max77686.c b/drivers/mfd/max77686.c
> index 8650832..d193873 100644
> --- a/drivers/mfd/max77686.c
> +++ b/drivers/mfd/max77686.c
> @@ -32,8 +32,10 @@
>  #include <linux/mfd/core.h>
>  #include <linux/mfd/max77686.h>
>  #include <linux/mfd/max77686-private.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/err.h>
>  #include <linux/of.h>
> +#include <linux/export.h>
>  
>  #define I2C_ADDR_RTC	(0x0C >> 1)
>  
> @@ -101,9 +103,119 @@ static const struct of_device_id max77686_pmic_dt_match[] = {
>  	{},
>  };
>  
> +static void max77686_dt_parse_dvs_gpio(struct device *dev)
> +{
> +	struct max77686_platform_data *pd = dev_get_platdata(dev);
> +	int i;
> +
> +	/*
> +	 * NOTE: we don't consider GPIO errors fatal; board may have some lines
> +	 * directly pulled high or low and thus doesn't specify them.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_dvs); i++)
> +		pd->buck_gpio_dvs[i] =
> +			devm_gpiod_get_index(dev, "max77686,pmic-buck-dvs", i);
> +
> +	for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++)
> +		pd->buck_gpio_selb[i] =
> +			devm_gpiod_get_index(dev, "max77686,pmic-buck-selb", i);
> +}

Not sure why you've pulled this out for parse_dt_pdata()?

> +/**
> + * max77686_setup_gpios() - init DVS-related GPIOs
> + * @dev: device whose platform data contains the dvs GPIOs information
> + *
> + * This function claims / initalizations GPIOs related to DVS if they are

s/initialzations/initialises

> + * defined. This may have the effect of switching voltages if the

s/if the/if

> + * pdata->buck_default_idx does not match the boot time state of pins.
> + */
> +int max77686_setup_gpios(struct device *dev)
> +{
> +	struct max77686_platform_data *pd = dev_get_platdata(dev);
> +	int buck_default_idx = pd->buck_default_idx;

You're saving 4 characters once here.  Just use the variable in pd.

> +	int ret;
> +	int i;

Don't you want some locking around this?

> +	/* Set all SELB high to avoid glitching while DVS is changing */
> +	for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++) {
> +		struct gpio_desc *gpio = pd->buck_gpio_selb[i];
> +
> +		/* OK if some GPIOs aren't defined */
> +		if (IS_ERR(gpio))
> +			continue;
> +
> +		ret = gpiod_direction_output_raw(gpio, 1);
> +		if (ret) {
> +			dev_err(dev, "can't set gpio[%d] dir: %d\n", i, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/* Set our initial setting */
> +	for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_dvs); i++) {
> +		struct gpio_desc *gpio = pd->buck_gpio_dvs[i];
> +
> +		/* OK if some GPIOs aren't defined */
> +		if (IS_ERR(gpio))
> +			continue;
> +
> +		/* If a GPIO is valid, set it */
> +		gpiod_direction_output(gpio, (buck_default_idx >> i) & 1);
> +		if (ret) {
> +			dev_err(dev, "can't set gpio[%d]: dir %d\n", i, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/* Now set SELB low to take effect */
> +	for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++) {
> +		struct gpio_desc *gpio = pd->buck_gpio_selb[i];
> +
> +		if (!IS_ERR(gpio))
> +			gpiod_set_value(gpio, 0);
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(max77686_setup_gpios);
> +
> +/**
> + * max77686_read_gpios() - read the current state of the dvs GPIOs
> + * @pdata: platform data that contains the dvs GPIOs information
> + *
> + * We call this function at bootup to detect what slot the firmware was
> + * using for the DVS GPIOs.  That way we can properly preserve the firmware's
> + * voltage settings
> + *
> + * This function can sleep so must not be called from atomic context.
> + */
> +int max77686_read_gpios(struct max77686_platform_data *pdata)
> +{
> +	int buck_default_idx = pdata->buck_default_idx;

Remove this, it adds very little.

> +	int result = 0;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(pdata->buck_gpio_dvs); i++) {
> +		struct gpio_desc *gpio = pdata->buck_gpio_dvs[i];
> +
> +		/* OK if some GPIOs aren't defined; we'll use default */
> +		if (IS_ERR(gpio)) {
> +			result |= buck_default_idx & (1 << i);

s/(1 << i)/BIT(i)/

> +			continue;
> +		}
> +
> +		if (gpiod_get_value_cansleep(gpio))
> +			result |= 1 << i;

Same here.

> +	}
> +
> +	return result;
> +}
> +EXPORT_SYMBOL_GPL(max77686_read_gpios);
> +
>  static struct max77686_platform_data *max77686_i2c_parse_dt_pdata(struct device
>  								  *dev)
>  {
> +	struct device_node *np = dev->of_node;
>  	struct max77686_platform_data *pd;
>  
>  	pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
> @@ -111,6 +223,13 @@ static struct max77686_platform_data *max77686_i2c_parse_dt_pdata(struct device
>  		return NULL;
>  
>  	dev->platform_data = pd;
> +
> +	/* Read default index and ignore errors, since default is 0 */
> +	of_property_read_u32(np, "max77686,pmic-buck-default-dvs-idx",

If it doesn't already have one, this needs a DT Ack and associated
documentation.

> +			     &pd->buck_default_idx);
> +
> +	max77686_dt_parse_dvs_gpio(dev);

Bring code back into here and remove the call.

>  	return pd;
>  }
>  
> diff --git a/include/linux/mfd/max77686.h b/include/linux/mfd/max77686.h
> index 4cbcc13..46a736b 100644
> --- a/include/linux/mfd/max77686.h
> +++ b/include/linux/mfd/max77686.h
> @@ -99,15 +99,17 @@ struct max77686_platform_data {
>  	struct max77686_opmode_data *opmode_data;
>  
>  	/*
> -	 * GPIO-DVS feature is not enabled with the current version of
> -	 * MAX77686 driver. Buck2/3/4_voltages[0] is used as the default
> -	 * voltage at probe. DVS/SELB gpios are set as OUTPUT-LOW.
> +	 * GPIO-DVS feature is not fully enabled with the current version of
> +	 * MAX77686 driver, but the driver does support using a DVS index other
> +	 * than the default of 0.
>  	 */
> -	int buck234_gpio_dvs[3]; /* GPIO of [0]DVS1, [1]DVS2, [2]DVS3 */
> -	int buck234_gpio_selb[3]; /* [0]SELB2, [1]SELB3, [2]SELB4 */
> -	unsigned int buck2_voltage[8]; /* buckx_voltage in uV */
> -	unsigned int buck3_voltage[8];
> -	unsigned int buck4_voltage[8];
> +	struct gpio_desc *buck_gpio_dvs[3]; /* GPIO of [0]DVS1, [1]DVS2, [2]DVS3 */
> +	int buck_default_idx; /* Default value of DVS1, 2, 3 */
> +
> +	struct gpio_desc *buck_gpio_selb[3]; /* Buck regulators 2, 3, 4 */
>  };
>  
> +extern int max77686_setup_gpios(struct device *dev);
> +extern int max77686_read_gpios(struct max77686_platform_data *pdata);
> +
>  #endif /* __LINUX_MFD_MAX77686_H */

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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