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    SubjectRe: [PATCH v7 08/24] mfd: max77686: Add Dynamic Voltage Scaling (DVS) support
    From
    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
    >
    >
    > _______________________________________________
    > linux-arm-kernel mailing list
    > linux-arm-kernel@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


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