Hi Sjoerd, > Hey Lukasz, > > Blame the holiday season for my late reply ;) > > On Fri, 2014-12-19 at 17:13 +0100, Lukasz Majewski wrote: > > Hi Guenter, > > > > > On Fri, Dec 19, 2014 at 04:32:24PM +0100, Lukasz Majewski wrote: > > > > Hi Sjoerd, > > > > > > > > Thanks for your feedback and sorry for a late reply. > > > > > > > > > On Thu, 2014-12-18 at 11:13 +0100, Lukasz Majewski wrote: > > > > > > Several new properties to allow PWM fan working as a cooling > > > > > > device have been combined into this single commit. > > > > > > > > > > > > Signed-off-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx> > > > > > > --- > > > > > > .../devicetree/bindings/hwmon/pwm-fan.txt | 28 > > > > > > ++++++++++++++++++++++ 1 file changed, 28 insertions(+) > > > > > > > > > > > > diff --git > > > > > > a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt > > > > > > b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt index > > > > > > 610757c..3877810 100644 --- > > > > > > a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt +++ > > > > > > b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt @@ > > > > > > -3,10 +3,38 @@ Bindings for a fan connected to the PWM > > > > > > lines Required properties: > > > > > > - compatible : "pwm-fan" > > > > > > - pwms : the PWM that is used to control the > > > > > > PWM fan +- cooling-pwm-values : PWM duty cycle values > > > > > > relative to > > > > > > + cooling-max-pwm-value > > > > > > correspondig to > > > > > > + proper cooling states > > > > > > +- default-pulse-width : Property specifying default > > > > > > pulse width for FAN > > > > > > + at system boot (zero to disable > > > > > > FAN on boot). > > > > > > + Allowed range is 0 to 255 > > > > > > > > > > The 0..255 range seems somewhat random. Would be nicer to > > > > > either use the approach of pwm-backlight (iotw, have the > > > > > range go from the first to the last entry of > > > > > cooling-pwm-values) > > > > > > > > I'm OK to change the default-pulse-width to be similar to > > > > "default-brightness-level" (as it is in > > > > Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt) > > > > > > > > > or simply have be the duty > > > > > lenght in NS as entries instead of the current indirection. > > > > > > > > I'd prefer to keep the indirection - as it is utilized in the > > > > current pwm-fan.c driver. > > > > > > > FWIW, devicetree information is supposed to be implementation > > > independent. So this is a poor argument. > > > > Many other pwm drivers use the indirection - e.g. mentioned > > pwm-backlight. > > I don't specifically mind the indirection, i was just thinking out > loud whether it added value (but if it's quite common, might indeed > be good to keep the pattern). What i do dislike is the number of > levels is being set to an arbitrary levels, as that will very rarely > match the actual number of distinct pwm levels you > > One thing though, when following the pattern of the pwm-backlight > driver; In pwm-backlight the highest index of brightness-levels is > always 100% duty cycle.. On e.g. XU3 the vendor kernel never drives > the fan at 100% duty (maximum of 91%). So it would be nice if the dt > bindigns could model that e.g. by having: > > pwm-levels = <20>; // 21 distinct pwm levels > valid-pwm-level = <5 15 18>; /* 5 15 and 18 are usable levels - pwm > will default to highest level */ > Could you review v2 of this patch series? http://www.spinics.net/lists/devicetree/msg63159.html > > > > > Enabling pan to full RPM was the default behaviour in the > > > > current pwm-fan.c file. > > > > > > > > To be honest, there is no need to enable fan to full RPM speed > > > > in this board for following reasons: > > > > 1. In Odroid the FAN is optional (stacked on top of a heat > > > > sink) - very often it is just enough to only have the heat sink. > > > > > > > > 2. Odroid has thermal enabled by default and IMHO it would be > > > > more feasible to allow thermal to control fan from the very > > > > beginning. > > > > > > > > However, I can also understand if the policy for hwmon implies a > > > > rule to enable by default all fans to full RPM speed. > > > > > > > Why and how does that all suggest that the current default > > > behavior should be changed ? > > > > I wanted to avoid the unpleasant sound for full speed fan when > > thermal is not enabled by default. > > > > But as I said, I fully understand the policy and I would be happy to > > comply with it as thermal should reduce the fan speed anyway at boot > > time. > > Yeah, what happens on my XU3 is that u-boot sets the pwm to 100% duty > and the thermal infrastructure turns it off as soon as it gets into > control, which works quite nicely (and keeps my sanity as that fan at > 100% is *loud*)... So if you want to avoid unpleasant sounds, just > build with thermal :p > > -- 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
