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Date: Thu, 9 May 2024 12:35:37 +0200
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Subject: Re: Aw: Re: [RFC v1 5/5] arm64: dts: mediatek: Add mt7986 based
 Bananapi R3 Mini
To: Frank Wunderlich <linux@fw-web.de>,
 Frank Wunderlich <frank-w@public-files.de>
Cc: Rob Herring <robh@kernel.org>,
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From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
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Il 09/05/24 12:30, Frank Wunderlich ha scritto:
> Am 9. Mai 2024 12:10:59 MESZ schrieb AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>:
>> 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@collabora.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>;
> 
> Thanks for clearing structure of the comment,but imho actually it is a driver issue (for all mtk SoC). Not sure it is really a hardware limitation. So i would change this to "... and the PWM driver does not support polarity inversion."
> 
>>>>>>> +		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!
> 
> Ok,i can try to add the property to binding (independ of this series). Imho label was cleaner than function and function-enumerator...
> 

Oh I sort of agree with you, I liked the label more, as it's more consistent with
everything else... but oh well. :-)

>> 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.
> 
> Don't worry, we are all humas...i missed looking in linux-next for the other binding-patches.
> 
>> P.S.: This shouldn't have been a RFC, as the patches are more than RFC quality!!!
> 
> I sent it as RFC because i had not expected to be merged before next is closed.
> 

Ah at least from my side, no worries... when I see RFC I generally expect to see
"dubious/head-scratching stuff", not "sub-optimal timing to send a patch" :-P

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>;
> 
> 
> regards Frank