On Thu, Sep 07, 2023 at 07:17:55AM +0000, Billy Tsai wrote: > On Wed, Aug 30, 2023 at 08:32:00PM +0800, Billy Tsai wrote: > >> From: Naresh Solanki <naresh.solanki@xxxxxxxxxxxxx> > >> > >> Add common fan properties bindings to a schema. > >> > >> Bindings for fan controllers can reference the common schema for the > >> fan > >> +properties: > >> + max-rpm: > >> + description: > >> + Max RPM supported by fan. > >> + $ref: /schemas/types.yaml#/definitions/uint32 > > > Physics will limit this to something much less than 2^32. Add some > > constraints. 10000? > > > >> + > >> + min-rpm: > >> + description: > >> + Min RPM supported by fan. > >> + $ref: /schemas/types.yaml#/definitions/uint32 > > > ditto > > >> + > >> + pulses-per-revolution: > >> + description: > >> + The number of pulse from fan sensor per revolution. > >> + $ref: /schemas/types.yaml#/definitions/uint32 > > >Needs constraints. I assume this is never more than 4 (or 2 even)? > > Do you think we should add the contraint in the common binding? > In my option, the limit of the max/min rpm should be declared by > the binding if necessary, because the usage of each fan monitor is > based on the connection of the tach pin. Yes, I think we should have default limits. Unless we go as far as a schema for every specific fan model, then there is actually no way we can have specific limits unless the fan controllers have some limits. The most I see in tree for pulses-per-revolution is 2. There's no value in more. So set the max to 4 and then if anyone needs more they can bump the value. Or maybe there's some electrical/mechanical design reason fans are 1 or 2 pulses and we'll never see anything else? This document[1] seems to indicate that is indeed the case. (First hit googling "fan tach signal pulses") > > > >> + div: > > > Too generic of a name. > > >> + description: > >> + Fan clock divisor > > > But what is a fan clock? > > This is the divisor for the tachometer sampling clock, which determines the sensitivity of the tach pin. > So, if the name of the property changes to 'tach-div,' is it acceptable to you? That sounds like a property of the controller, not the fan, so it belongs in the controller binding. Is this really a common thing? > >> + $ref: /schemas/types.yaml#/definitions/uint32 > >> + > >> + target-rpm: > >> + description: > >> + Target RPM the fan should be configured during driver probe. > > > What driver? By the time the OS driver runs, a bunch of other boot > > software has already run on modern systems. So this value would likely > > be used much earlier. The point is that when exactly is outside the > > scope of DT. This is "what RPM do I use in case of no other information > > (e.g. temperature)". > > So, the description should be changed to 'The default desired fan speed in RPM,' > and we shouldn't mention the timing of the property's operation in the DT, is that correct? Correct. > > >> + $ref: /schemas/types.yaml#/definitions/uint32 > >> + > >> + mode: > > > Too generic. > > >> + description: > >> + Select the operational mode of the fan. > > > What are modes? Spin and don't spin? > > The mode is used to indicate the driving mode of the fan (DC, PWM and so on). > So, if the name of the property changes to 'fan-driving-mode,' is it acceptable to you? I tend to think that should be implied from the parent node and/or other properties. PWM if "pwms" property is present. DC if the supply is variable. We could also use compatible strings in the fan nodes if there's a need. That reminds me, both of these modes probably need a table of voltage/duty-cycle to RPMs. I imagine it's not always a linear response. Naresh also privately sent me (don't do that) an updated common binding which we discussed the need for this. I expect him to comment further with details. > >> + $ref: /schemas/types.yaml#/definitions/uint32 > >> + > >> + pwms: > >> + description: > >> + PWM provider. > > > maxItems: 1 > > > I don't think there are fans with more than 1 PWM input? > > Ok, I will add the constraint for the pwm input. > > >> + > >> + tach-ch: > >> + description: > >> + The tach channel used for the fan. > >> + $ref: /schemas/types.yaml#/definitions/uint32 > > > The existing ASpeed version of this property allows more than 1 entry. I > > don't understand how a fan would have 2 tach signals, but if so, the > > generic property should allow for that. > > Ok, I will modify it to the uint32-array Perhaps uint8-array to align with existing versions of the property. > > > Perhaps 'reg' should be defined in here with some text saying 'reg' > > corresponds to the fan controller specific id which may be the PWM+TACH > > channel, PWM channel (deprecated), or TACH channel. I think there are > > examples of all 3 of these cases. > > I don't think it's necessary for the 'reg' because the case you mentioned is > already covered by the property 'tach-ch' and the 'pwms'. Yes, but when we have N child nodes of the same thing, we usually have "reg" and its value corresponds to how the parent identifies each child. We already have a mixture using PWM or tach channel. Yes, this can all just be in the fan controllers binding, but putting it here would just document the options. Rob [1] http://www.comairrotron.com/methods-monitoring-fan-performance
