On Fri, 2015-04-10 at 06:09 -0700, Guenter Roeck wrote: > On 04/10/2015 05:59 AM, Anand Moon wrote: > > Hi Sjoerd, > > > > I don't much advance knowledge on internal signaling of pwm-samsung module. > > > > So do I need to send this patch again ? > > > > From the context, it seems that the fix in hwmon would only paint > over a problem in the actual pwm driver, correct ? Yes/no/maybe :). Imho this is something to clarify in the pwm API documentation. As currently all it says is: "pwm_disable - stop a PWM output toggling", Which is what the exynos driver does. Thierry, could you clearify what the intention is here? I'm happy to prepare a pwm driver patch if needed to solve this? > If you resubmit the patch I would expect you to explain this in the > commit log. > > Guenter > > > -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
