linux-kernel - Re: [linux-sunxi] [PATCH v2] arm64: allwinner: a64: Add A64-OLinuXino initial support

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Date:   Mon, 14 Aug 2017 17:13:52 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Jagan Teki <jagannadh.teki@...il.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Support - OLIMEX Ltd <support@...mex.com>,
        Jagan Teki <jagan@...rulasolutions.com>
Subject: Re: [linux-sunxi] [PATCH v2] arm64: allwinner: a64: Add A64-OLinuXino
 initial support

On Mon, Aug 14, 2017 at 5:09 PM, Jagan Teki <jagannadh.teki@...il.com> wrote:
> On Mon, Aug 14, 2017 at 1:26 PM, Chen-Yu Tsai <wens@...e.org> wrote:
>> On Mon, Aug 14, 2017 at 3:34 PM, Jagan Teki <jagannadh.teki@...il.com> wrote:
>>> On Mon, Aug 14, 2017 at 12:38 PM, Chen-Yu Tsai <wens@...e.org> wrote:
>>>> Hi,
>>>>
>>>> On Sun, Aug 13, 2017 at 1:54 AM, Jagan Teki <jagannadh.teki@...il.com> wrote:

[...]

>>>>> +&reg_dcdc1 {
>>>>> +       regulator-always-on;
>>>>> +       regulator-min-microvolt = <3300000>;
>>>>> +       regulator-max-microvolt = <3300000>;
>>>>> +       regulator-name = "vcc-3v3";
>>>>> +};
>>>>> +
>>>>> +&reg_dcdc2 {
>>>>> +       regulator-always-on;
>>>>> +       regulator-min-microvolt = <1100000>;
>>>>> +       regulator-max-microvolt = <1100000>;
>>>>
>>>> The SoC has a wider range than a fixed voltage for the CPUs.
>>>
>>> So, max 1.1v can't enough CPUs? thought similar behavior with pine64?
>>
>> The recommended operating conditions says 1.04 ~ 1.3 V for CPUx,
>> while the typical voltage is 1.1V. The regulator constraints should
>> match the datasheet, especially for power rails that are involved in
>> DVFS.
>
> power rails from datasheet[1] shows 0.5v ~ 1.3v am I not looking
> updated details?

The constraints are there to prevent users from setting a voltage
too high or too low for the connected devices.

You should be looking at the recommended operating conditions
for the A64. The regulator constraints should match the constraints
of the consumer, not the provider. If there are multiple consumers,
it must match the narrowest range supported by _all_ consumers, i.e.
the intersection of all consumer's operating ranges.

ChenYu

>
> [1] http://files.pine64.org/doc/datasheet/pine64/AXP803_Datasheet_V1.0.pdf
>
> thanks!
> --
> Jagan Teki
> Free Software Engineer | www.openedev.com
> U-Boot, Linux | Upstream Maintainer
> Hyderabad, India.