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

[Javier Martinez Canillas]

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);
+}
+
+/**
+ * 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);
+
+	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];
+	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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