linux-kernel - Re: [PATCH] regulator: qcom-rpmh: Fix pm8010 pmic5

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Date: Wed, 14 Feb 2024 22:47:09 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Mark Brown <broonie@...nel.org>
Cc: andersson@...nel.org, konrad.dybcio@...aro.org, lgirdwood@...il.com,
 quic_fenglinw@...cinc.com, quic_collinsd@...cinc.com,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: qcom-rpmh: Fix pm8010 pmic5_pldo502ln minimum
 voltage

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.

---
bod