Hi Willy, Am Samstag, 11. Februar 2017, 18:45:54 CET schrieb Willy Tarreau: > On Sat, Feb 11, 2017 at 05:33:16PM +0100, Heiko Stuebner wrote: > > Am Samstag, 11. Februar 2017, 09:56:55 CET schrieb Willy Tarreau: > > > The MiQi board is sold with an enclosure in which a fan is connected > > > to the second LED output, and configured by default in "heartbeat" > > > mode so that it rotates slowly and increases when the CPU load > > > increases, ensuring appropriate cooling by default. This LED output > > > is called "Fan" in the original kernel and connected to GPIO18 > > > (gpiochip 0, pin 18). Here we called it "miqi:green:fan" to stay > > > consistent with the kernel's naming conventions. > > > > I tend to disagree with this approach. A fan is not a led and the > > devicetree is about describing the hardware, not how a specific kernel > > likes to use things> > > :-) . > > Sure but I was trying to stay as close as possible to the intended > purpose of the connector on the board as it is sold :-) > > > The kernel already has a gpio-fan driver (drivers/hwmon) or you could > > resurrect the gpio-pwm patch [0] from Olliver Schinagl and use the pwm-fan > > on top of that for more intermediate steps. > > Ah it's great to know there has already been something like this because > I thought about developing one for the same reason. > > > > It's worth noting that without this patch the fan doesn't work at > > > all, risking to make the board overheat. > > > > At least cpufreq is already hooked to the thermal controller on the > > rk3288, so even without additional cooling it should select lower cpu > > frequencies keeping the heat in line and prevent overheating the board. > > Well that's one way to see it, as for me throttling the CPU is the last > resort before seeing it die ; That's what I was trying to say :-) ... it won't overheat because cpufreq will throttle it as a last resort. > I find it sad to waste all the performance > of a 3288 that way, otherwise it's easier to use something like a dirt > a much slower and cheaper cortex A5. But I agree with the point regarding > the gpio-pwm. Even with the gpio-fan you should see results if you simply add the fan as active trip point somewhere before the cpufreq trip points. So let the fan get activated at 50/60° or so. Heiko > I think that mqmaker initially designed the GPIO to be used > as a led to benefit from the heartbeat trigger which more or less replaces > what a more efficient thermal control could achieve. -- 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
