Hi Sjoerd, I don't much advance knowledge on internal signaling of pwm-samsung module. So do I need to send this patch again ? -Anand Moon On 10 April 2015 at 17:30, Sjoerd Simons <sjoerd.simons@xxxxxxxxxxxxxxx> wrote: > Hey Anand, > > On Fri, 2015-04-10 at 16:58 +0530, Anand Moon wrote: >> Hi Guenter/Lukasz, >> >> Earlier I send v2 version of the patch spiking this one. >> >> Markus Riechl came back to me with below mail. >> So This patch confirms fixes the bug. >> >> I will send v3 version of the patch. Earlier I was in delima about the bug. >> >> -Anand Moon >> ------------------------------------------- >> Hi Anand, >> >> I tested your patch. >> >> After booting the fan is spinning despite only 44°C. >> >> /sys/class/thermal/cooling_device0/curstate is 0. >> /sys/class/hwmon/hwmon4/pwm1 is 0 >> >> when I echo 1 > cur_state and then echo 0 > cur_state again, >> the fan switches to off and behaves as expected. >> >> It looks like there is a bug in initializing the pwm output >> immediately after booting. > > The problem here will be that at boot the PWM runs at full duty. With > the current exynos PWM drive if you disable the PWM it will stop pulsing > but remain high if it was at 100% duty. My patch on which you depend > upon fixed a race where disabling the pwm right after changing the duty > cycle (e.g. to 0%) also kept the signal high. > > From looking at other PWM users at the time it seemed that most if not > all always first set to duty to 0% and then disable the pwm. Which > should work fine on exynos now. However iirc Thierry recently clarified > that the expected result of pwm_disable is not just that the modulation > stops but also that the output signal goes low, although that's not very > explicit in the current pwm documentation.. The exynos PWM driver will > need another fix tweak to make that true. > > > >> Best Regards, > > > >> -- >> Markus Reichl >> >> On 8 April 2015 at 23:19, Anand Moon <linux.amoon@xxxxxxxxx> wrote: >> > Hi Guenter, >> > >> > Sorry my blunder mistake. Sorry for the noise. >> > >> > I just tested with spiking this patch and my observation and testing >> > were wrong we can skip this patch. >> > >> > I will send an v2 patch series removing the patch 5 and patch 6. >> > >> > With correct dts changes. >> > >> > Thanks for pointing my mistake. >> > >> > -Anand Moon >> > >> > On 8 April 2015 at 22:23, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >> >> On Wed, Apr 08, 2015 at 09:32:05PM +0530, Anand Moon wrote: >> >>> Hi Guenter, >> >>> >> >>> Initially the board bootup the cooling level state is 0. >> >>> So update the duty cycle and this power off the fan. >> >>> As their is no state change the fan will not spin. >> >>> >> >>> Once the temperature sensor is reached to alert temperature it changes state. >> >>> With the state change the fan cools the CPU and then stop's >> >>> >> >>> I have observed this state change with tmon utility in linux/tools/thermal/tmon/ >> >>> >> >> Sorry, I am missing something. I still don't see what problem you are fixing >> >> with this patch. What behavior is wrong with the current code, and how does your >> >> patch fix it ? >> >> >> >> Guenter >> >> >> >>> -Anand Moon >> >>> >> >>> On 8 April 2015 at 21:02, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >> >>> > On Wed, Apr 08, 2015 at 10:44:15AM +0200, Lukasz Majewski wrote: >> >>> >> Hi Anand, >> >>> >> >> >>> >> > Below changes depend on following patch. >> >>> >> > https://patchwork.kernel.org/patch/5944061/ >> >>> >> > >> >>> >> > Update the pwm_config with duty then update the pwm_disable >> >>> >> > to poweroff the cpu fan. >> >>> >> > >> >>> > >> >>> > Unfortunately, the patch does not include an explanation why it is needed. >> >>> > >> >>> > The original code presumably did not update the duty cycle because >> >>> > pwm was about to be disabled anyway. That kind of made sense to me. >> >>> > Updating the duty cycle to 0 just to disable the pwm channel right >> >>> > afterwards does not immediately make sense. >> >>> > >> >>> > Given that, I would expect to see a rationale here. Why is this patch needed ? >> >>> > Does it fix a bug ? If yes, pelase describe the bug. If not, what is the >> >>> > purpose of this patch ? >> >>> > >> >>> > Maybe that is all explained in patch 0/6, which I was not copied on. Even >> >>> > if so, the reationale will be needed in the changelog to explain to future >> >>> > developers why this change was made. >> >>> > >> >>> > Thanks, >> >>> > Guenter >> >>> > >> >>> >> > Tested on OdroidXU3 board. >> >>> >> > >> >>> >> > Signed-off-by: Anand Moon <linux.amoon@xxxxxxxxx> >> >>> >> > --- >> >>> >> > drivers/hwmon/pwm-fan.c | 10 ++++------ >> >>> >> > 1 file changed, 4 insertions(+), 6 deletions(-) >> >>> >> > >> >>> >> > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c >> >>> >> > index 7c83dc4..f25c841 100644 >> >>> >> > --- a/drivers/hwmon/pwm-fan.c >> >>> >> > +++ b/drivers/hwmon/pwm-fan.c >> >>> >> > @@ -44,26 +44,24 @@ static int __set_pwm(struct pwm_fan_ctx *ctx, >> >>> >> > unsigned long pwm) int ret = 0; >> >>> >> > >> >>> >> > mutex_lock(&ctx->lock); >> >>> >> > + >> >>> > >> >>> > [ please refrain from unnecessary whitespace changes ] >> >>> > >> >>> >> > if (ctx->pwm_value == pwm) >> >>> >> > goto exit_set_pwm_err; >> >>> >> > >> >>> >> > - if (pwm == 0) { >> >>> >> > - pwm_disable(ctx->pwm); >> >>> >> > - goto exit_set_pwm; >> >>> >> > - } >> >>> >> > - >> >>> >> > duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM); >> >>> >> > ret = pwm_config(ctx->pwm, duty, ctx->pwm->period); >> >>> >> > if (ret) >> >>> >> > goto exit_set_pwm_err; >> >>> >> > >> >>> >> > + if (pwm == 0) >> >>> >> > + pwm_disable(ctx->pwm); >> >>> >> > + >> >>> >> > if (ctx->pwm_value == 0) { >> >>> >> > ret = pwm_enable(ctx->pwm); >> >>> >> > if (ret) >> >>> >> > goto exit_set_pwm_err; >> >>> >> > } >> >>> >> > >> >>> >> > -exit_set_pwm: >> >>> >> > ctx->pwm_value = pwm; >> >>> >> > exit_set_pwm_err: >> >>> >> > mutex_unlock(&ctx->lock); >> >>> >> >> >>> >> Reviewed-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx> >> >>> >> >> >>> >> BTW: I've added Guenter to CC. >> >>> >> >> >>> >> -- >> >>> >> Best regards, >> >>> >> >> >>> >> Lukasz Majewski >> >>> >> >> >>> >> Samsung R&D Institute Poland (SRPOL) | Linux Platform Group > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
