Subject: Re: [PATCH 2/2] arm64: dts: marvell: clearfog-gt-8k: set SFP power limit

From: Baruch Siach <[email-masked]>
Date: Sun, 19 May 2019 21:25:03 +0300

Hi Russell,

On Sun, May 19 2019, Russell King wrote:
> On Sun, May 19, 2019 at 12:21:06PM +0300, Baruch Siach wrote:
>> The Clearfog GT-8K board is capable of supplying power up to 2A to SFP
>> modules. Make that explicit in the device-tree. Without this property
>> current kernel does not allow SFP modules that require more than 1A.
>
> I do hope you're aware that current is not the same thing as power!
> You say above "2A" which is a current, but the maximum power figure
> below is "2W".  Given that modules are supplied with 3.3V, and
> Power = Voltage x Current, this really doesn't work out!
>
> Please can you correct both of your patches for accuracy in this
> regard, thanks.

My bad. I'll fix and resend.

Thanks for reviewing.

baruch

>> Signed-off-by: Baruch Siach <[email-masked]>
>> ---
>>  arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts b/arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts
>> index 9143aa13ceb1..f275d9420d5b 100644
>> --- a/arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts
>> +++ b/arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts
>> @@ -63,6 +63,7 @@
>>  		tx-disable-gpio = <&cp1_gpio1 29 GPIO_ACTIVE_HIGH>;
>>  		pinctrl-names = "default";
>>  		pinctrl-0 = <&cp0_sfp_present_pins &cp1_sfp_tx_disable_pins>;
>> +		maximum-power-milliwatt = <2000>;
>>  	};
>>  
>>  	leds {

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