linux-kernel - Re: Aw: Re: [RFC v1 5/5] arm64: dts: mediatek: Add mt7986 based Bananapi R3 Mini

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Date: Thu, 9 May 2024 12:10:59 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Frank Wunderlich <frank-w@...lic-files.de>
Cc: Frank Wunderlich <linux@...web.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Eric Woudstra <ericwouds@...il.com>, Tianling Shen <cnsztl@...ortalwrt.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-leds@...r.kernel.org,
 netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, Tianling Shen <cnsztl@...il.com>
Subject: Re: Aw: Re: [RFC v1 5/5] arm64: dts: mediatek: Add mt7986 based
 Bananapi R3 Mini

Il 08/05/24 20:25, Frank Wunderlich ha scritto:
> Hi
> 
>> Gesendet: Dienstag, 07. Mai 2024 um 15:35 Uhr
>> Von: "AngeloGioacchino Del Regno" <angelogioacchino.delregno@...labora.com>
>>
>> Il 06/05/24 18:00, Frank Wunderlich ha scritto:
> 
>>>>> +	fan: pwm-fan {
>>>>> +		compatible = "pwm-fan";
>>>>> +		#cooling-cells = <2>;
>>>>> +		/* cooling level (0, 1, 2) - pwm inverted */
>>>>> +		cooling-levels = <255 96 0>;
>>>>
>>>> Did you try to actually invert the PWM?
>>>>
>>>> Look for PWM_POLARITY_INVERTED ;-)
>>>
>>> Mtk pwm driver does not support it
>>>
>>> https://elixir.bootlin.com/linux/latest/source/drivers/pwm/pwm-mediatek.c#L211
>>>
>>
>> You're right, sorry - I confused the general purpose PWM controller with the
>> rather specific DISP_PWM controller (which does support polarity inversion).
>>
>> It's good - but I'd appreciate if you can please add a comment stating that
>> the PWM values are inverted in SW because the controller does *not* support
>> polarity inversion... so that next time someone looks at this will immediately
>> understand what's going on and why :-)
> 
> so i would change comment like this:
> 
> 		/* cooling level (0, 1, 2)
> 		 * signal is inverted on board
> 		 * mtk pwm driver does not support
> 		 * PWM_POLARITY_INVERTED */
> 

There you go:

/*
  * The signal is inverted on this board and the general purpose
  * PWM HW IP in this SoC does not support polarity inversion.
  */
/* Cooling level < 0  1  2> */
cooling-levels = <255 96 0>;



>>>>> +		pwms = <&pwm 0 10000>;
>>>>> +		status = "okay";
>>>>> +	};
>>>>> +
>>>>> +	phy14: ethernet-phy@14 {
> ...
>>>>> +		interrupts-extended = <&pio 48 IRQ_TYPE_EDGE_FALLING>;
>>>>> +		reset-gpios = <&pio 49 GPIO_ACTIVE_LOW>;
>>>>> +		reset-assert-us = <10000>;
>>>>> +		reset-deassert-us = <20000>;
>>>>> +		phy-mode = "2500base-x";
>>>>> +		full-duplex;
>>>>> +		pause;
>>>>> +		airoha,pnswap-rx;
>>>>> +
>>>>> +		leds {
>>>>> +			#address-cells = <1>;
>>>>> +			#size-cells = <0>;
>>>>> +
>>>>> +			led@0 { /* en8811_a_gpio5 */
>>>>> +				reg = <0>;
>>>>> +				color = <LED_COLOR_ID_YELLOW>;
>>>>> +				function = LED_FUNCTION_LAN;
>>>>> +				function-enumerator = <1>;
>>>>
>>>> Why aren't you simply using a label?
>>>
>>> You mean the comment? I can add it of course like for regulators.
>>>
>>
>> I mean in place of the function-enumerator... that's practically used to
>> distinguish between instances, it's not too common to see it, and usually
>> "label" replaces exactly that - just that, instead of a different number,
>> it gets a different name with no (usually) meaningless numbers :-)
> 
> as far as i understand using label also makes "function" property useless, after discussing
> this with eric i would drop both on all 4 places by labels like these:
> 
> label = "yellow-lan";
> label = "green-lan";
> ...
> 
> not sure if we should drop color property too...
> 

I'm looking at the leds binding (leds/common.yaml) right now.

My suggestion of using 'label' was actually wrong - and your devicetree was
actually right!!! (apart from the default-trigger that may not work)

Infact, the documentation says, in brief:

- function-enumerator is ignored if label is present
- function doesn't say that gets ignored
- color doesn't say that gets ignored
- label says:
   - If not present -> get string from node name
   - function-enumerator ignored
   - This property is deprecated

..but the 'label' binding does not say 'deprecated: true', which is something
that must be fixed!


So, I'm sorry for the confusion, the noise and the useless loss of time around
this - you can keep the LED nodes as they are, and that's a lesson for the future
me reviewing another node like this one.

P.S.: This shouldn't have been a RFC, as the patches are more than RFC quality!!!

Cheers,
Angelo

>>>>> +				default-state = "keep";
>>>>> +				linux,default-trigger = "netdev";
>>>>> +			};
>>>>> +			led@1 { /* en8811_a_gpio4 */
>>>>> +				reg = <1>;
>>>>> +				color = <LED_COLOR_ID_GREEN>;
>>>>> +				function = LED_FUNCTION_LAN;
>>>>> +				function-enumerator = <2>;
>>>>> +				default-state = "keep";
>>>>> +				linux,default-trigger = "netdev";
>>>>> +			};
>>>>> +		};
>>>>> +	};
>>>>> +
>>>>> +	phy15: ethernet-phy@15 {
>>>>> +		reg = <15>;
>>>>
>>>> Same here.
>>>>
>>>> Cheers,
>>>> Angelo
> 
> regards Frank