linux-kernel - Re: [PATCH v7 1/6] DONOTMERGE: arm64: dts: ti: Add TI TPS65219 PMIC support for AM642 SK board.

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Date:   Wed, 28 Dec 2022 10:16:27 +0000
From:   Wadim Egorov <W.Egorov@...tec.de>
To:     Mark Brown <broonie@...nel.org>, Nishanth Menon <nm@...com>
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Subject: Re: [PATCH v7 1/6] DONOTMERGE: arm64: dts: ti: Add TI TPS65219 PMIC
 support for AM642 SK board.

Am 16.12.22 um 14:41 schrieb Mark Brown:
> On Thu, Dec 15, 2022 at 03:41:49PM -0600, Nishanth Menon wrote:
>
>> Yeah - this happens to be SDcard supply (at least in my case).. I'd
>> rather not change the mmc host or core layer to handle a case where
>> LDO happened to be in bypass. it is a regulator driver's problem, IMHO
>> how to provide the stated voltage OR fail to transition the voltage.
> Well, if the regulator is in bypass mode then it is by definition not
> regulating and so it's like programming the voltage while switched off,
> setting the target for when it starts regulating again.  It's a weirder
> use case but it does feel like the consistent thing to do at least.
> The driver shouldn't enter/leave bypass without being explicitly told to
> so since there'll be a performance impact.
>
>> b) If I wanted the LDO to poweroff the bypass bit at start (define the
>>     startup hardware condition), I dont seem to have a description for
>>     that either.
> That's something we could add in constraints, though the actual process
> of implementing it might get messy if there's restrictions like having
> to power off (though from further down the thread I see that might not
> apply to this device).

Just for the record:

My reported problem was actually not the LDO1/bypass situation, but an issue in 
the process of resolving the regulator supplies.

It was resolved by
   commit 0debed5b117d ("regulator: core: Fix resolve supply lookup issue")

Now everything seems to work with my setup with LDO1 supplied by a fixed 
regulator and LDO1 acting in bypass mode on our hardware.

Regards,
Wadim