Re: [PATCH] regulator: qcom-rpmh: Fix pm8010 pmic5_pldo502ln minimum voltage

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On 2/20/2024 4:20 PM, Bryan O'Donoghue wrote:
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.


Got feedback from the chip designer: "1.808V is the typical digital Vset logic output – always round up to the integer multiples of 8mV. However, 1.8V is a more commonly used output. So we made analog only change, move the tap point of the reference generator to 1.8V when it is programmed to 1.808V. If user program it to 1.8V, digital logic will round it up to 1.808V, send it to analog, then analog will map it to 1.8V. So the end result is the same regardless customer program it to 1.8V or 1.808V from PMIC register point of view. "

So, programming it to either 1.8V or 1.808V, the HW will output 1.8V. I understand there is a problem for x1e801000 because its AOP side limits the voltage range to [1.808V, 1.808V] for LDO3/4/6 power rails, it won't work if linux side updates to use 1.8V. Actually the same issue applies to SM8550 and SM8650 if you simply update the voltage level to 1.808V, because their AOP side limits the voltage ranges for some of these LDOs to [1.8V, 1.8V].

One possible fix is just adding 1.808v as another level for these LDOs.

Fenglin

---
bod





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