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

From: amit daniel kachhap
Date: Thu Jul 10 2014 - 06:00:03 EST

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

>
> 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);
> +}
> +
> +/**
> + * 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@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/