Hi Heiko, On Sat, Feb 11, 2017 at 05:33:16PM +0100, Heiko Stuebner wrote: > Hi Willy, > > 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 ; 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. 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. Thanks! Willy -- 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
