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

Hello Lee,

Thanks a lot for your feedback.

On 07/09/2014 05:13 PM, Lee Jones wrote:

I'd really like Linus Walleij to look over this if possible.

Ok, I'll cc Linus when posting the next version of the series.

On Fri, 04 Jul 2014, Javier Martinez Canillas wrote:

quoted

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);
+}

Not sure why you've pulled this out for parse_dt_pdata()?

Ok, I'll remove that function and put the code in max77686_i2c_parse_dt_pdata().

quoted

+/**
+ * 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

s/initialzations/initialises

Right, will fix the typo.

quoted

+ * defined. This may have the effect of switching voltages if the

s/if the/if

Ditto.

quoted

+ * 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;

You're saving 4 characters once here.  Just use the variable in pd.

Ok

quoted

+	int ret;
+	int i;

Don't you want some locking around this?

This function is only called in the max77686 and max77802 regulator drivers
probe functions and we expect to have either one of those in a system but never
both so this function can't really be executed concurrently.

And even in the case that a system has both max77686 and max77802 PMICs, all the
data accessed is local to the driver's struct device so I think there is no need
to add any locking here.

quoted

+	/* 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;

Remove this, it adds very little.

Ok.

quoted

+	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);

s/(1 << i)/BIT(i)/

Ok.

quoted

+			continue;
+		}
+
+		if (gpiod_get_value_cansleep(gpio))
+			result |= 1 << i;

Same here.

Ok.

quoted

+	}
+
+	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",

If it doesn't already have one, this needs a DT Ack and associated
documentation.

Yes, these DT binding properties are documented in Patch 17/24 "mfd: max77686:
Add documentation for DVS bindings" and I've cc'ed devicetree at vger.kernel.org so
hopefully I can get some feedback/ack from DT maintainers.

quoted

+			     &pd->buck_default_idx);
+
+	max77686_dt_parse_dvs_gpio(dev);

Bring code back into here and remove the call.

Sure, will do.

quoted

 	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 */

Best regards,
Javier