linux-kernel - Re: [PATCH] regulator: rk808: Fix min

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Date:	Mon, 6 Oct 2014 21:54:41 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Chris Zhong <zyw@...k-chips.com>
Cc:	Mark Brown <broonie@...nel.org>,
	Heiko Stübner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: rk808: Fix min_uV for DCDC1 & DCDC2

Chris and Mark,

On Mon, Oct 6, 2014 at 8:29 PM, Chris Zhong <zyw@...k-chips.com> wrote:
>
> On 10/01/2014 06:52 AM, Mark Brown wrote:
>>
>> On Tue, Sep 30, 2014 at 06:57:51PM +0200, Heiko Stübner wrote:
>>>
>>> Am Dienstag, 30. September 2014, 09:43:47 schrieb Doug Anderson:
>>>>
>>>> On Tue, Sep 30, 2014 at 2:44 AM, Chris Zhong <zyw@...k-chips.com> wrote:
>>>>>
>>>>> -       REGULATOR_LINEAR_RANGE(700000, 0, 63, 12500),
>>>>> +       REGULATOR_LINEAR_RANGE(712500, 0, 63, 12500),
>>>>
>>>> I have no problem with this (and the current "dts" file I see don't go
>>>> this low anyway), but it doesn't match the datasheet I have right now
>>>> which says "0.700 V" is the min.
>>>
>>> Then it would be problem.
>>> The original statement above says, that a register value of "0" equals
>>> 700mV,
>>> so changing this in this way would mean everything runs 12.5mV above the
>>> target voltage.
>>> And I can confirm, that the current datasheet lists 700mV as equallying
>>> register value 0.
>>
>> Has anyone got a voltmeter?
>
> The latest datasheet has fixed this error.
> The register value of "0" equals 712.5mV, so the max value can reach 1.5v
> but not 1.4875v.

OK, that sounds like this is the right change, then.

To Mark's point, I measured voltage using the builtin voltage
measurement feature this board (not 100% sure the accuracy / precision
guarantees on them, but...):

Asked for 1.300 volts on vdd_arm (dcdc1).
* Before: got 1.326
* After: got 1.310

Asked for 1.3 on vdd_gpu (dcdc2):
* Before: 1.326
* After: got 1.314

Asked for 1.0 on vdd_gpu:
* Before: 1.038
* After: got 1.026

Asked for .8 on vdd_gpu
* Before:.836
* After: got .822


It almost sounds like we're still running a little too high for
voltages, but this gets us in the right direction I guess.

-Doug
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