[PATCH v3 1/2] regulator: pwm: Add support for a fixed delay after duty cycle changes

Douglas Anderson
2016-08-31T04:21:15Z

From: Matthias Kaehlcke <mka-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

A change of the duty cycle doesn't necessarily cause an immediate switch
to the target voltage. On many PWM regulators there is a fixed "settle
time" (irrespective of the jump size) that we need to wait after an
upward jump. This change introduces the device tree property
"settle-time-up-us" which allows us to specify a fixed delay after a
voltage increase.

We don't add an option of a fixed delay on the way down for now because
the way down is probably modelled best with a ramp rate, not a fixed
delay.

Signed-off-by: Matthias Kaehlcke <mka-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Signed-off-by: Douglas Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
Changes in v3:
- Took out fixed delay for falling transitions
- Updated description

.../devicetree/bindings/regulator/pwm-regulator.txt | 6 ++++++
drivers/regulator/pwm-regulator.c | 19 +++++++++++++++----
2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
index 3aeba9f86ed8..9dc15d18e787 100644
--- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
+++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
@@ -34,6 +34,12 @@ Only required for Voltage Table Mode:
First cell is voltage in microvolts (uV)
Second cell is duty-cycle in percent (%)

+Optional properties:
+--------------------
+- settle-time-up-us: Time to settle down after a voltage increase
+ (unit: us). For regulators with a ramp delay
+ the two values are added.
+
Optional properties for Continuous mode:
- pwm-dutycycle-unit: Integer value encoding the duty cycle unit. If not
defined, <100> is assumed, meaning that
diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c
index c24524242da2..94f1ca3b793d 100644
--- a/drivers/regulator/pwm-regulator.c
+++ b/drivers/regulator/pwm-regulator.c
@@ -48,6 +48,8 @@ struct pwm_regulator_data {

/* Enable GPIO */
struct gpio_desc *enb_gpio;
+
+ u32 settle_time_up_us;
};

struct pwm_voltages {
@@ -195,6 +197,7 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
unsigned int max_uV_duty = drvdata->continuous.max_uV_dutycycle;
unsigned int duty_unit = drvdata->continuous.dutycycle_unit;
unsigned int ramp_delay = rdev->constraints->ramp_delay;
+ unsigned int delay = 0;
int min_uV = rdev->constraints->min_uV;
int max_uV = rdev->constraints->max_uV;
int diff_uV = max_uV - min_uV;
@@ -233,12 +236,17 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
return ret;
}

- if ((ramp_delay == 0) || !pwm_regulator_is_enabled(rdev))
+ if (req_min_uV > old_uV)
+ delay = drvdata->settle_time_up_us;
+
+ if (ramp_delay != 0)
+ /* Adjust ramp delay to uS and add to settle time. */
+ delay += DIV_ROUND_UP(abs(req_min_uV - old_uV), ramp_delay);
+
+ if ((delay == 0) || !pwm_regulator_is_enabled(rdev))
return 0;

- /* Ramp delay is in uV/uS. Adjust to uS and delay */
- ramp_delay = DIV_ROUND_UP(abs(req_min_uV - old_uV), ramp_delay);
- usleep_range(ramp_delay, ramp_delay + DIV_ROUND_UP(ramp_delay, 10));
+ usleep_range(delay, delay + DIV_ROUND_UP(delay, 10));

return 0;
}
@@ -368,6 +376,9 @@ static int pwm_regulator_probe(struct platform_device *pdev)
if (!init_data)
return -ENOMEM;

+ of_property_read_u32(np, "settle-time-up-us",
+ &drvdata->settle_time_up_us);
+
config.of_node = np;
config.dev = &pdev->dev;
config.driver_data = drvdata;
--
2.8.0.rc3.226.g39d4020