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

[amit daniel kachhap <amit.daniel@samsung.com>]

On Sat, Jul 5, 2014 at 1:54 AM, Javier Martinez Canillas
<javier.martinez@collabora.co.uk> 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.

The entire series looks nice. Few minor comments from my side. I guess
still one more version in needed as per other ppls comment.
You may add,
Reviewed-by: Amit Daniel Kachhap <amit.daniel@samsung.com>

>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> ---
>
> 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);
> +}
> +
> +/**
> + * 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
> + * defined. This may have the effect of switching voltages if the
> + * 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;
> +       int ret;
> +       int i;
> +
> +       /* 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;
> +       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);
> +                       continue;
> +               }
> +
> +               if (gpiod_get_value_cansleep(gpio))
> +                       result |= 1 << i;
> +       }
> +
> +       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",
> +                            &pd->buck_default_idx);
Any error checking code here. Say if pmic-buck-default-dvs-idx exceed 8?
> +
> +       max77686_dt_parse_dvs_gpio(dev);
> +
>         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];
I think when DVS gpio is used all the 8 voltage levels are fetched
from DT during booting and the registers are programmed accordingly.
Any further set/get_voltage just changes the GPIO lines.
Any reason why this method is not used?
> +       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 */
> --
> 2.0.0.rc2
>
>
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