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Date: Tue, 20 Feb 2024 08:20:41 +0000
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Subject: Re: [PATCH] regulator: qcom-rpmh: Fix pm8010 pmic5_pldo502ln minimum
 voltage
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To: Fenglin Wu <quic_fenglinw@quicinc.com>, Mark Brown <broonie@kernel.org>
Cc: andersson@kernel.org, konrad.dybcio@linaro.org, lgirdwood@gmail.com,
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References: <20240214121614.2723085-1-bryan.odonoghue@linaro.org>
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From: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
In-Reply-To: <6f6dfaa2-f529-c9fe-7dde-402c92f0daf6@quicinc.com>
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On 19/02/2024 3:06 a.m., Fenglin Wu wrote:
> 
> 
> On 2024/2/15 6:47, Bryan O'Donoghue wrote:
>> On 14/02/2024 14:52, Mark Brown wrote:
>>> On Wed, Feb 14, 2024 at 02:44:56PM +0000, Bryan O'Donoghue wrote:
>>>> On 14/02/2024 14:13, Mark Brown wrote:
>>>
>>>>> Not just that but also note that every voltage step in the range will
>>>>> have the 8mV offset added.
>>>
>>>> The documents I have just show sensors attached to ldo3, ldo4 and 
>>>> ldo6 fixed
>>>> at 1.808.
>>>
>>>> I don't think there's any better or different information than a 
>>>> +200000uV
>>>> increment TBH.
>>>
>>> This seems like a very surprising and unusual hardware design, the
>>> 1.808V voltage is already unusual.  Note that this may break systems
>>> that are trying to set a range of say 1.8-2.0V if they actually need to
>>> set 2V.
>>
>> Hmm. I'm sure the rail value should be 1.808 its all over the 
>> documentation for example when we get to index 3 we hit 2608000
>>
>> REGULATOR_LINEAR_RANGE(1808000, 0,  2,  200000),
>> 1808000 0
>> 2008000 1
>> 2208000 2
>> 2408000 x
>> REGULATOR_LINEAR_RANGE(2608000, 3,  28, 16000),
>>
>> And there are other rails @ 1v8 if 1v8
>>
>> The one thing I can't easily verify is index 0 = 1808000 and not say 
>> 1800000 or indeed that the increment is 200000 and not say 8000.
>>
>> I'll see if I can ask around with the hw people and get a more 
>> complete answer.
>>
>> Similarly now that you've gotten me digging into this problem, it's 
>> not clear to me why this regulator isn't just a linear regulator with 
>> an 8mv increment over a range of indexes.
>>
>> At least the documentation I'm looking at doesn't elucidate.
>>
>> I'll dig some more.
> Please see the voltage steps for LDO3/4/6 described in the PM8010 TDOS 
> document which is the most authoritative that we used internally for 
> PMIC driver development:

I will look - however

1. The powertree internal docs for xe801000 show 1.808 rails derived
    from 1.856 rails for camera sensors

2. Publicly available with registration : 80-185821-1
 
https://docs.qualcomm.com/bundle/80-18582-1/resource/80-18582-1_REV_AV_PM8010_Data_Sheet.pdf

    Table 3-7 Linear/low-voltage regulator summary

    Specified programmable range (V)
    ldo3, ldo4, ldo6 = 1.808 to 3.312

3. The pmic ranges I'm looking at on the internal
    show increases of 8000 mv linearly

> And I do see from the document change history that step 0 was changed 
> from 1808mV and step 2 was changed from 2512mV, I don't know the reason 
> of the change though.

Hrmm...

OK, that's enough to investigate further.

---
bod