Re: [PATCHv1 2/3] arm: mvebu: add .dts file for Synology DS213j

[Ben Peddell <klightspeed-aslSrjg9ejhWX4hkXwHRhw@public.gmane.org>]

On 17/11/14 18:25, Arnaud Ebalard wrote:
> Hi,
> 
> Ben Peddell <klightspeed-aslSrjg9ejhWX4hkXwHRhw@public.gmane.org> writes:
> 
>> On 16/11/2014 11:14 PM, Arnaud Ebalard wrote:
>>>>> +	gpio-fan-100-32-35 {
>>>> There is some logic to this naming, but i don't remember what it is.
>>>> Did you check this is appropriate?
>>> The 32-35 is for the MPP i.e. fan uses mpp32 to mpp35 (3 MPP for speed,
>>> one for alarm). I don't know what the 100 part means. What I did is I
>>> googled to see which fan supported kirkwood models have and noticed
>>> that the DS212j uses the exact same fan, i.e. Y.S.Tech FD129225LL-N so
>>> I opted for the same naming.
>>>
>>> On that aspect, you may be able to explain why the speed-map for this
>>> fan goes up to 5000 RPM. This fan is supposed to operate at 1900RPM.
>>> Note that it does not matter in practice.
>>
>> On the Kirkwood Diskstations, the first number (100, 120 or 150) refers
>> to the middle of the three fan speed resistors,
> 
> Would not have found that alone ;-) Thanks for clarifying.
> 
>> the second number (15 or
>> 32) refers to the first fan control pin, and the third number (18 or 35)
>> refers to the first fan alarm pin.
>>
>> i.e. the 100-32-35 uses fan speed resistors of 33, 100 and 150 ohms,
>> uses pins 32-34 for fan control, and uses pin 35 for the fan alarm.
>>
>> The 5000RPM was interpolated from my measured RPM pulse rate (4200PPM)
>> of the 80mm fan in my DS211j (which uses the 150-32-35 fan config) at
>> maximum RPM.
> 
> Then, I think I need to change the speed map to have 1900 RPM as max
> speed. Out of curiosity, how did you measured the RPM pulse rate
> exactly?

I hooked a logic analyzer to the sense pin and measured the pulse rate.

Looking at the specifications of the fan in this unit (an EC7025L12ER),
it has a maximum fan speed of 3000RPM, so it looks like it uses two
pulses per revolution and not one as I had assumed when I created the
speed map.
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