| Message ID | 1472617277-30814-1-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Aug 30, 2016 at 09:21:15PM -0700, Douglas Anderson wrote: > 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. Why is this specific to regulators implemented with PWM controllers? Most DCDCs have a PWM element and the concept of a hard time limit for transition rather than a ramp rate doesn't seem like it'd be unique.
On Tue, Aug 30, 2016 at 09:21:15PM -0700, Douglas Anderson wrote: > From: Matthias Kaehlcke <mka@chromium.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@chromium.org> > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- > Changes in v3: > - Took out fixed delay for falling transitions > - Updated description > > .../devicetree/bindings/regulator/pwm-regulator.txt | 6 ++++++ Acked-by: Rob Herring <robh@kernel.org> > drivers/regulator/pwm-regulator.c | 19 +++++++++++++++---- > 2 files changed, 21 insertions(+), 4 deletions(-)
On Fri, Sep 02, 2016 at 10:11:51AM -0500, Rob Herring wrote: > On Tue, Aug 30, 2016 at 09:21:15PM -0700, Douglas Anderson wrote: > > From: Matthias Kaehlcke <mka@chromium.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@chromium.org> > > Signed-off-by: Douglas Anderson <dianders@chromium.org> > > --- > > Changes in v3: > > - Took out fixed delay for falling transitions > > - Updated description > > > > .../devicetree/bindings/regulator/pwm-regulator.txt | 6 ++++++ > > Acked-by: Rob Herring <robh@kernel.org> I take that back. What Mark said... > > > 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;