On Mon, Feb 23, 2015 at 06:43:16AM -0800, Guenter Roeck wrote: > On 02/23/2015 06:34 AM, Simon Guinot wrote: > >On Mon, Feb 23, 2015 at 06:06:12AM -0800, Guenter Roeck wrote: > >>On 02/23/2015 04:58 AM, Simon Guinot wrote: > >>>On some boards, such as the LaCie 2Big Network v2 or 2Big NAS (based on > >>>Marvell Kirkwood SoCs), an I2C fan controller is used but the alarm > >>>signal is wired to a separate GPIO. Unfortunately, the gpio-fan driver > >>>can't be used to handle GPIO alarm alone from DT: an error is returned > >>>if the "gpios" DT property is missing. > >>> > >>>This patch allows to use the gpio-fan driver even if the "alarm-gpios" > >>>DT property is defined alone. > >>> > >> > >>That is the wrong solution. The gpio alarm signal should be handled > >>by the fan controller driver. > > > >Hi Guenter, > > > >Sure it should, but unfortunately it is not the case. I have several > >boards using this mechanism (ie: a separate fan alarm GPIO). I think the > >idea was to reduce the board cost... > > > Well, yes, the driver for the fan controller chip needs to be updated > to support interrupts. This will not help for the boards I mentioned. As an attempt to reduce the board cost, a fan with 2 wires has been used. This means we don't have any tachymeter feedback and then the controller alarm mechanism can't be used. Instead a kind of hardware hack allows to have a fan alarm on a separate GPIO. > > >Then this means I need a way to support this alarm signal and I can't > >find a better one than using gpio-fan. Note that this was possible with > >the original gpio-fan implementation (before the DT binding addition). > > > > That doesn't help. Handle the GPIO fan alarm feature from the fan controller driver don't look good either to me. This alarm mechanism is not a part of the fan controller itself but rather something apart. Also I am afraid that the result would really look like a hack. Simon > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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