| Message ID | 1467830521-15300-1-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thursday 07 July 2016 12:12 AM, Douglas Anderson wrote: > The original commit adding support for continuous voltage mode didn't > handle the regulator ramp delay properly. It treated the delay as a > fixed delay in uS despite the property being defined as uV / uS. Let's > adjust it. Luckily there appear to be no users of this ramp delay for > PWM regulators (as per grepping through device trees in linuxnext). > > Note also that the upper bound of usleep_range probably shouldn't be a > full 1 ms longer than the lower bound since I've seen plenty of hardware > with a ramp rate of ~5000 uS / uV and for small jumps the total delays > are in the tens of uS. 1000 is way too much. We'll try to be dynamic > and use 10%. > > NOTE: This commit doesn't add support for regulator-enable-ramp-delay. > That could be done in a future patch when someone has a user of that > featre. > > Though this patch is shows as "fixing" a bug, there are no actual known > users of continuous mode PWM regulator w/ ramp delay in mainline and so > this likely won't have any effect on anyone unless they are working > out-of-tree with private patches. For anyone in this state, it is > highly encouraged to also pick Boris Brezillon's WIP patches to get > yourself a reliable and glitch-free regulator. > > Fixes: 4773be185a0f ("regulator: pwm-regulator: Add support for continuous-voltage") > Signed-off-by: Douglas Anderson <dianders@chromium.org> Looks fine here. Acked-by: Laxman Dewangan <ldewangan@nvidia.com> BTW, for some PWM regulator, the settling time for voltage change is same for any steps.
Hi, On Thu, Jul 7, 2016 at 1:36 AM, Laxman Dewangan <ldewangan@nvidia.com> wrote: > > On Thursday 07 July 2016 12:12 AM, Douglas Anderson wrote: >> >> The original commit adding support for continuous voltage mode didn't >> handle the regulator ramp delay properly. It treated the delay as a >> fixed delay in uS despite the property being defined as uV / uS. Let's >> adjust it. Luckily there appear to be no users of this ramp delay for >> PWM regulators (as per grepping through device trees in linuxnext). >> >> Note also that the upper bound of usleep_range probably shouldn't be a >> full 1 ms longer than the lower bound since I've seen plenty of hardware >> with a ramp rate of ~5000 uS / uV and for small jumps the total delays >> are in the tens of uS. 1000 is way too much. We'll try to be dynamic >> and use 10%. >> >> NOTE: This commit doesn't add support for regulator-enable-ramp-delay. >> That could be done in a future patch when someone has a user of that >> featre. >> >> Though this patch is shows as "fixing" a bug, there are no actual known >> users of continuous mode PWM regulator w/ ramp delay in mainline and so >> this likely won't have any effect on anyone unless they are working >> out-of-tree with private patches. For anyone in this state, it is >> highly encouraged to also pick Boris Brezillon's WIP patches to get >> yourself a reliable and glitch-free regulator. >> >> Fixes: 4773be185a0f ("regulator: pwm-regulator: Add support for >> continuous-voltage") >> Signed-off-by: Douglas Anderson <dianders@chromium.org> > > > > Looks fine here. > Acked-by: Laxman Dewangan <ldewangan@nvidia.com> > > BTW, for some PWM regulator, the settling time for voltage change is same > for any steps. In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" or something? ...and actually the right thing is probably to implement 'regulator-ramp-delay' as doing several small steps in that case. So if you've got: * settle time: 10 us * ramp delay = 5000 uV / us * voltage change of 200000 uV In that case you'd probably want to break your 200 mV voltage change into a few steps? So you could do bump by 50mV, delay 10us, bump by 50mV, delay 10us, bump by 50mV, delay by 10us. The final delay would be the same as with my patch applied but you'd get there more smoothly. -Doug
Hi, >> In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" or something? >> Looks reasonable to me. >> actually the right thing is probably to implement 'regulator-ramp-delay' as doing several small steps in that case >> Ramp delay uV/us is not a "real" metric for some PWM regulators with exponential transition -- as opposite to fixed slew-rate linear transition on other regulators. So splitting transition into multiple steps to implement artificial (in this case) metric seems questionable. -----Original Message----- From: dianders@google.com [mailto:dianders@google.com] On Behalf Of Doug Anderson Sent: Thursday, July 07, 2016 9:31 AM To: Laxman Dewangan Cc: Mark Brown; Boris Brezillon; Lee Jones; Brian Norris; open list:ARM/Rockchip SoC...; Heiko Stuebner; Thierry Reding; Liam Girdwood; linux-kernel@vger.kernel.org; Aleksandr Frid Subject: Re: [PATCH v2] regulator: pwm: Fix regulator ramp delay for continuous mode Hi, On Thu, Jul 7, 2016 at 1:36 AM, Laxman Dewangan <ldewangan@nvidia.com> wrote: > > On Thursday 07 July 2016 12:12 AM, Douglas Anderson wrote: >> >> The original commit adding support for continuous voltage mode didn't >> handle the regulator ramp delay properly. It treated the delay as a >> fixed delay in uS despite the property being defined as uV / uS. >> Let's adjust it. Luckily there appear to be no users of this ramp >> delay for PWM regulators (as per grepping through device trees in linuxnext). >> >> Note also that the upper bound of usleep_range probably shouldn't be >> a full 1 ms longer than the lower bound since I've seen plenty of >> hardware with a ramp rate of ~5000 uS / uV and for small jumps the >> total delays are in the tens of uS. 1000 is way too much. We'll try >> to be dynamic and use 10%. >> >> NOTE: This commit doesn't add support for regulator-enable-ramp-delay. >> That could be done in a future patch when someone has a user of that >> featre. >> >> Though this patch is shows as "fixing" a bug, there are no actual >> known users of continuous mode PWM regulator w/ ramp delay in >> mainline and so this likely won't have any effect on anyone unless >> they are working out-of-tree with private patches. For anyone in >> this state, it is highly encouraged to also pick Boris Brezillon's >> WIP patches to get yourself a reliable and glitch-free regulator. >> >> Fixes: 4773be185a0f ("regulator: pwm-regulator: Add support for >> continuous-voltage") >> Signed-off-by: Douglas Anderson <dianders@chromium.org> > > > > Looks fine here. > Acked-by: Laxman Dewangan <ldewangan@nvidia.com> > > BTW, for some PWM regulator, the settling time for voltage change is > same for any steps. In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" or something? ...and actually the right thing is probably to implement 'regulator-ramp-delay' as doing several small steps in that case. So if you've got: * settle time: 10 us * ramp delay = 5000 uV / us * voltage change of 200000 uV In that case you'd probably want to break your 200 mV voltage change into a few steps? So you could do bump by 50mV, delay 10us, bump by 50mV, delay 10us, bump by 50mV, delay by 10us. The final delay would be the same as with my patch applied but you'd get there more smoothly. -Doug
Hi, On Thu, Jul 7, 2016 at 11:23 AM, Aleksandr Frid <afrid@nvidia.com> wrote: > Hi, > >>> > In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" > or something? >>> > Looks reasonable to me. > >>> > actually the right thing is probably to implement 'regulator-ramp-delay' as doing several small steps in that case >>> > Ramp delay uV/us is not a "real" metric for some PWM regulators with exponential transition -- as opposite to fixed slew-rate linear transition on other regulators. So splitting transition into multiple steps to implement artificial (in this case) metric seems questionable. In the case that you don't need multiple steps then don't specify a regulator-ramp-delay, just a pwm-regulator-settle-us. ...the suggestion for multiple steps is because (so I'm told) it helps avoid overshoot or undershoot problems. In general the whole point of ramping a regulator slowly is to avoid overshoot or undershoot problems. The "regulator-ramp-delay" property in Linux is a little odd because it sort of "describes" the ramp delay and sort of "sets" the ramp delay. Many PMICs allow you to set how fast the regulator will ramp and this property is used to specify how the register in the PMIC should be set. However, it is also used as the actual delay in Linux. -Doug
>> In the case that you don't need multiple steps then don't specify a regulator-ramp-delay, just a pwm-regulator-settle-us. >> Agreed -----Original Message----- From: dianders@google.com [mailto:dianders@google.com] On Behalf Of Doug Anderson Sent: Thursday, July 07, 2016 11:32 AM To: Aleksandr Frid Cc: Laxman Dewangan; Mark Brown; Boris Brezillon; Lee Jones; Brian Norris; open list:ARM/Rockchip SoC...; Heiko Stuebner; Thierry Reding; Liam Girdwood; linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] regulator: pwm: Fix regulator ramp delay for continuous mode Hi, On Thu, Jul 7, 2016 at 11:23 AM, Aleksandr Frid <afrid@nvidia.com> wrote: > Hi, > >>> > In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" > or something? >>> > Looks reasonable to me. > >>> > actually the right thing is probably to implement > 'regulator-ramp-delay' as doing several small steps in that case >>> > Ramp delay uV/us is not a "real" metric for some PWM regulators with exponential transition -- as opposite to fixed slew-rate linear transition on other regulators. So splitting transition into multiple steps to implement artificial (in this case) metric seems questionable. In the case that you don't need multiple steps then don't specify a regulator-ramp-delay, just a pwm-regulator-settle-us. ...the suggestion for multiple steps is because (so I'm told) it helps avoid overshoot or undershoot problems. In general the whole point of ramping a regulator slowly is to avoid overshoot or undershoot problems. The "regulator-ramp-delay" property in Linux is a little odd because it sort of "describes" the ramp delay and sort of "sets" the ramp delay. Many PMICs allow you to set how fast the regulator will ramp and this property is used to specify how the register in the PMIC should be set. However, it is also used as the actual delay in Linux. -Doug
On Thu, Jul 07, 2016 at 06:43:33PM +0000, Aleksandr Frid wrote: I'm not entirely sure what's wrong with your mail client here but your mails are essentially illegible. There appears to be some combination of top posting, reflowing quoted content to remove line breaks and extra levels of quoting. > >> > In the case that you don't need multiple steps then don't specify a regulator-ramp-delay, just a pwm-regulator-settle-us. > >> > Agreed > > -----Original Message----- > From: dianders@google.com [mailto:dianders@google.com] On Behalf Of Doug Anderson > Sent: Thursday, July 07, 2016 11:32 AM > To: Aleksandr Frid > Cc: Laxman Dewangan; Mark Brown; Boris Brezillon; Lee Jones; Brian Norris; open list:ARM/Rockchip SoC...; Heiko Stuebner; Thierry Reding; Liam Girdwood; linux-kernel@vger.kernel.org > Subject: Re: [PATCH v2] regulator: pwm: Fix regulator ramp delay for continuous mode > > Hi, > > On Thu, Jul 7, 2016 at 11:23 AM, Aleksandr Frid <afrid@nvidia.com> wrote: > > Hi, > > > >>> > > In that case we should probably add a new PWM regulator property and not abuse the existing one. Maybe you use "pwm-regulator-settle-us" > > or something? > >>> > > Looks reasonable to me. > > > >>> > > actually the right thing is probably to implement > > 'regulator-ramp-delay' as doing several small steps in that case > >>> > > Ramp delay uV/us is not a "real" metric for some PWM regulators with exponential transition -- as opposite to fixed slew-rate linear transition on other regulators. So splitting transition into multiple steps to implement artificial (in this case) metric seems questionable. > > In the case that you don't need multiple steps then don't specify a regulator-ramp-delay, just a pwm-regulator-settle-us. > > ...the suggestion for multiple steps is because (so I'm told) it helps avoid overshoot or undershoot problems. In general the whole point of ramping a regulator slowly is to avoid overshoot or undershoot problems. The "regulator-ramp-delay" property in Linux is a little odd because it sort of "describes" the ramp delay and sort of "sets" > the ramp delay. Many PMICs allow you to set how fast the regulator will ramp and this property is used to specify how the register in the PMIC should be set. However, it is also used as the actual delay in Linux. > > > -Doug
diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c index ab3cc0235843..75d9f9b1ad62 100644 --- a/drivers/regulator/pwm-regulator.c +++ b/drivers/regulator/pwm-regulator.c @@ -132,6 +132,7 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev, unsigned int duty_pulse; u64 req_period; u32 rem; + int old_uV = pwm_regulator_get_voltage(rdev); int ret; pwm_get_args(drvdata->pwm, &pargs); @@ -161,8 +162,12 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev, drvdata->volt_uV = min_uV; - /* Delay required by PWM regulator to settle to the new voltage */ - usleep_range(ramp_delay, ramp_delay + 1000); + if ((ramp_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(min_uV - old_uV), ramp_delay); + usleep_range(ramp_delay, ramp_delay + DIV_ROUND_UP(ramp_delay, 10)); return 0; }
The original commit adding support for continuous voltage mode didn't handle the regulator ramp delay properly. It treated the delay as a fixed delay in uS despite the property being defined as uV / uS. Let's adjust it. Luckily there appear to be no users of this ramp delay for PWM regulators (as per grepping through device trees in linuxnext). Note also that the upper bound of usleep_range probably shouldn't be a full 1 ms longer than the lower bound since I've seen plenty of hardware with a ramp rate of ~5000 uS / uV and for small jumps the total delays are in the tens of uS. 1000 is way too much. We'll try to be dynamic and use 10%. NOTE: This commit doesn't add support for regulator-enable-ramp-delay. That could be done in a future patch when someone has a user of that featre. Though this patch is shows as "fixing" a bug, there are no actual known users of continuous mode PWM regulator w/ ramp delay in mainline and so this likely won't have any effect on anyone unless they are working out-of-tree with private patches. For anyone in this state, it is highly encouraged to also pick Boris Brezillon's WIP patches to get yourself a reliable and glitch-free regulator. Fixes: 4773be185a0f ("regulator: pwm-regulator: Add support for continuous-voltage") Signed-off-by: Douglas Anderson <dianders@chromium.org> --- Note: I don't have a board that works against mainline and can use the PWM regulator in continuous mode without Boris's patches. That means that this patch has only been compile tested. The previous version of the patches (atop Boris's changes) was tested more thoroughly. YMMV. Changes in v2: - No longer atop Boris PWM regulator fixes (Mark). - Don't delay if the regulator is not enabled (Boris). drivers/regulator/pwm-regulator.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)