[PATCH v2 8/9] regulator: pwm-regulator: Simplify voltage to duty-cycle call

Lee Jones
2015-07-07T15:08:22Z

If we reverse some of the logic and change the formula used,
we can simplify the function greatly.

It is intentional that this function is supplied and then re-worked
within the same patch-set. The submission in the previous patch is
the tried and tested (i.e. in real releases) method written by ST.
This patch contains a simplification provided later. It looks and
performs better, but doesn't have the same time-under-test that the
original method does. The idea is that we keep some history in
order to provide an easy way back i.e. revert.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/regulator/pwm-regulator.c | 27 +++++++--------------------
1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c
index dac145d..d5cb267 100644
--- a/drivers/regulator/pwm-regulator.c
+++ b/drivers/regulator/pwm-regulator.c
@@ -93,26 +93,13 @@ static int pwm_regulator_list_voltage(struct regulator_dev *rdev,
/**
* Continuous voltage call-backs
*/
-static int pwm_voltage_to_duty_cycle(struct regulator_dev *rdev,
- int volt_mV)
+static int pwm_voltage_to_duty_cycle(struct regulator_dev *rdev, int req_uV)
{
- struct pwm_regulator_data *drvdata = rdev_get_drvdata(rdev);
- int min_mV = rdev->constraints->min_uV / 1000;
- int max_mV = rdev->constraints->max_uV / 1000;
- int max_duty_cycle = drvdata->max_duty_cycle;
- int vdiff = min_mV - max_mV;
- int pwm_code;
- int tmp;
-
- tmp = ((max_duty_cycle - min_mV) * max_duty_cycle) / vdiff;
- pwm_code = ((tmp + max_duty_cycle) * volt_mV) / vdiff;
-
- if (pwm_code < 0)
- pwm_code = 0;
- if (pwm_code > max_duty_cycle)
- pwm_code = max_duty_cycle;
-
- return pwm_code * 100 / max_duty_cycle;
+ int min_uV = rdev->constraints->min_uV;
+ int max_uV = rdev->constraints->max_uV;
+ int diff = max_uV - min_uV;
+
+ return 100 - ((((req_uV * 100) - (min_uV * 100)) / diff));
}

static int pwm_regulator_get_voltage(struct regulator_dev *rdev)
@@ -131,7 +118,7 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
int duty_cycle;
int ret;

- duty_cycle = pwm_voltage_to_duty_cycle(rdev, min_uV / 1000);
+ duty_cycle = pwm_voltage_to_duty_cycle(rdev, min_uV);

ret = pwm_config(drvdata->pwm,
(drvdata->pwm->period / 100) * duty_cycle,
--
1.9.1