linux-kernel - Re: [PATCH 3/9] arm64: dts: allwinner: pinebook: Remove unused AXP803 regulators

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Date:   Tue, 21 Jan 2020 21:14:02 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH 3/9] arm64: dts: allwinner: pinebook: Remove unused AXP803
 regulators

On 1/21/20 3:05 AM, Maxime Ripard wrote:
> On Sun, Jan 19, 2020 at 10:30:58AM -0600, Samuel Holland wrote:
>> The Pinebook does not use the CSI bus on the A64. In fact it does not
>> use GPIO port E for anything at all. Thus the following regulators are
>> not used and do not need voltages set:
>>
>>  - ALDO1: Connected to VCC-PE only
>>  - DLDO3: Not connected
>>  - ELDO3: Not connected
>>
>> Signed-off-by: Samuel Holland <samuel@...lland.org>
>> ---
>>  .../boot/dts/allwinner/sun50i-a64-pinebook.dts   | 16 +---------------
>>  1 file changed, 1 insertion(+), 15 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
>> index ff32ca1a495e..8e7ce6ad28dd 100644
>> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
>> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
>> @@ -202,9 +202,7 @@
>>  };
>>
>>  &reg_aldo1 {
>> -	regulator-min-microvolt = <2800000>;
>> -	regulator-max-microvolt = <2800000>;
>> -	regulator-name = "vcc-csi";
>> +	regulator-name = "vcc-pe";
>>  };
> 
> If it's connected to PE, I'd expect the voltage to be at 3.3v?

If we provide voltage constraints, the regulator core will enable the regulator
and set its voltage at boot. That seems like a bit of a waste.

I don't think the voltage really matters, since nothing is plugged in to the
port. ALDO1 can't go over 3.3V anyway, so even if it does get turned on for some
reason, nothing will get damaged.

Samuel