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

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 <redacted>
Reviewed-by: Krzysztof Kozlowski <redacted>
---

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);
+}

+	}
+
+	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",

 	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 */