[U-Boot] [PATCH v2 6/9] regulator: Add support for ramp delay

Krzysztof Kozlowski
2019-02-13T16:46:45Z

Changing voltage and enabling regulator might require delays so the
regulator stabilizes at expected level.

Add support for "regulator-ramp-delay" binding which can introduce
required time to both enabling the regulator and to changing the
voltage.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
---
.../regulator/regulator.txt | 2 +
drivers/power/regulator/regulator-uclass.c | 47 ++++++++++++++++++-
include/power/regulator.h | 2 +
3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/doc/device-tree-bindings/regulator/regulator.txt b/doc/device-tree-bindings/regulator/regulator.txt
index 65b69c427899..4ba642b7c77f 100644
--- a/doc/device-tree-bindings/regulator/regulator.txt
+++ b/doc/device-tree-bindings/regulator/regulator.txt
@@ -35,6 +35,7 @@ Optional properties:
- regulator-max-microamp: a maximum allowed Current value
- regulator-always-on: regulator should never be disabled
- regulator-boot-on: enabled by bootloader/firmware
+- regulator-ramp-delay: ramp delay for regulator (in uV/us)

Note
The "regulator-name" constraint is used for setting the device's uclass
@@ -60,4 +61,5 @@ ldo0 {
regulator-max-microamp = <100000>;
regulator-always-on;
regulator-boot-on;
+ regulator-ramp-delay = <12000>;
};
diff --git a/drivers/power/regulator/regulator-uclass.c b/drivers/power/regulator/regulator-uclass.c
index 6f355b969a6d..363c6e6441fa 100644
--- a/drivers/power/regulator/regulator-uclass.c
+++ b/drivers/power/regulator/regulator-uclass.c
@@ -35,10 +35,22 @@ int regulator_get_value(struct udevice *dev)
return ops->get_value(dev);
}

+static void regulator_set_value_delay(struct udevice *dev, int old_uV,
+ int new_uV, unsigned int ramp_delay)
+{
+ int delay = DIV_ROUND_UP(abs(new_uV - old_uV), ramp_delay);
+
+ debug("regulator %s: delay %u us (%d uV -> %d uV)\n", dev->name, delay,
+ old_uV, new_uV);
+
+ udelay(delay);
+}
+
int regulator_set_value(struct udevice *dev, int uV)
{
const struct dm_regulator_ops *ops = dev_get_driver_ops(dev);
struct dm_regulator_uclass_platdata *uc_pdata;
+ int ret, old_uV = uV, is_enabled = 0;

uc_pdata = dev_get_uclass_platdata(dev);
if (uc_pdata->min_uV != -ENODATA && uV < uc_pdata->min_uV)
@@ -49,7 +61,20 @@ int regulator_set_value(struct udevice *dev, int uV)
if (!ops || !ops->set_value)
return -ENOSYS;

- return ops->set_value(dev, uV);
+ if (uc_pdata->ramp_delay) {
+ is_enabled = regulator_get_enable(dev);
+ old_uV = regulator_get_value(dev);
+ }
+
+ ret = ops->set_value(dev, uV);
+
+ if (!ret) {
+ if (uc_pdata->ramp_delay && old_uV > 0 && is_enabled)
+ regulator_set_value_delay(dev, old_uV, uV,
+ uc_pdata->ramp_delay);
+ }
+
+ return ret;
}

/*
@@ -107,6 +132,7 @@ int regulator_set_enable(struct udevice *dev, bool enable)
{
const struct dm_regulator_ops *ops = dev_get_driver_ops(dev);
struct dm_regulator_uclass_platdata *uc_pdata;
+ int ret, old_enable = 0;

if (!ops || !ops->set_enable)
return -ENOSYS;
@@ -115,7 +141,22 @@ int regulator_set_enable(struct udevice *dev, bool enable)
if (!enable && uc_pdata->always_on)
return -EACCES;

- return ops->set_enable(dev, enable);
+ if (uc_pdata->ramp_delay)
+ old_enable = regulator_get_enable(dev);
+
+ ret = ops->set_enable(dev, enable);
+ if (!ret) {
+ if (uc_pdata->ramp_delay && !old_enable && enable) {
+ int uV = regulator_get_value(dev);
+
+ if (uV > 0) {
+ regulator_set_value_delay(dev, 0, uV,
+ uc_pdata->ramp_delay);
+ }
+ }
+ }
+
+ return ret;
}

int regulator_set_enable_if_allowed(struct udevice *dev, bool enable)
@@ -335,6 +376,8 @@ static int regulator_pre_probe(struct udevice *dev)
-ENODATA);
uc_pdata->always_on = dev_read_bool(dev, "regulator-always-on");
uc_pdata->boot_on = dev_read_bool(dev, "regulator-boot-on");
+ uc_pdata->ramp_delay = dev_read_u32_default(dev, "regulator-ramp-delay",
+ 0);

/* Those values are optional (-ENODATA if unset) */
if ((uc_pdata->min_uV != -ENODATA) &&
diff --git a/include/power/regulator.h b/include/power/regulator.h
index 314160a894b7..6c6e2cd4f996 100644
--- a/include/power/regulator.h
+++ b/include/power/regulator.h
@@ -150,6 +150,7 @@ enum regulator_flag {
* @always_on* - bool type, true or false
* @boot_on* - bool type, true or false
* TODO(sjg at chromium.org): Consider putting the above two into @flags
+ * @ramp_delay - Time to settle down after voltage change (unit: uV/us)
* @flags: - flags value (see REGULATOR_FLAG_...)
* @name** - fdt regulator name - should be taken from the device tree
* ctrl_reg: - Control register offset used to enable/disable regulator
@@ -169,6 +170,7 @@ struct dm_regulator_uclass_platdata {
int max_uV;
int min_uA;
int max_uA;
+ unsigned int ramp_delay;
bool always_on;
bool boot_on;
const char *name;
--
2.17.1