Date:	Mon, 9 Feb 2015 14:08:41 -0800
From:	Bjorn Andersson <bjorn@...o.se>
To:	Mark Brown <broonie@...nel.org>
Cc:	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	"agross@...eaurora.org" <agross@...eaurora.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"patches@...nsource.wolfsonmicro.com" 
	<patches@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH 2/9] regulator: core: Introduce set_optimum_mode op

On Fri, Jan 30, 2015 at 4:27 AM, Mark Brown <broonie@...nel.org> wrote:
> On Thu, Jan 29, 2015 at 04:07:42PM -0800, Bjorn Andersson wrote:
>> On Wed 28 Jan 11:52 PST 2015, Mark Brown wrote:
>
>> > This is basically fine but can you please rename this to be something
>> > that more directly reflects the fact that we're just informing the
>> > driver about the operating parameters - there are other things a driver
>> > could usefully do with this, for example set current limits so that if
>> > something starts to consume excessive current the device will flag this
>> > as an error.
>
>> The purpose of the series was to be able to implement patch 9, which
>> will utilize the load_uA to set the "mode" of the Qualcomm regulators.
>
>> So I would like it to be a "setter of current consumption".
>
>> I'm not sure what to name the function to have it cover these additional
>> cases.
>
> notify_load() or something?  That's what it's doing, what the driver
> does with it is a separate thing.
>

I changed it to set_load() in my tree, maybe "notify" is better as
it's more of a hint to the driver.

You said something when we talked that I interpreted to
regulator_set_optimum_mode() is not a good name for the consumer API;
was that a correct interpretation or was your comment limited to the
driver facing API?

Should we go ahead and rename it to regulator_notify_load()
(regulator_set_load() perhaps?) before we get more consumers as well?
(would be a separate patch set)

>> > It'd also be better to split the voltage specs out into a separate
>> > function, especially for the output voltage where obviously we have a
>> > separate range based interface for setting that.
>
>> The current implementors of get_optimum_mode all ignore the voltages, so
>> we could effectively simplify the interface to:
>
>>  get_optimum_mode(rdev, load);
>
>> Question is if there are any implementations where we don't know the
>> output voltage in the regulator driver (as locking prevents us from
>> using the standard interface of querying this). Input voltage is just a
>> query away.
>
> We can always fix the locking to let people query the voltage if they
> need to.
>

Sounds good, drms_uA_update() becomes quite minimal with that.

But if we're only considering load in drms_uA_update() does it make
sense to check this against the valid ranges of min_uA, max_uA and
hence instead of checking REGULATOR_CHANGE_DRMS just check for
REGULATOR_CHANGE_CURRENT?
We have reduced the interface to not necessarily be dynamic _mode_ setting.

This would allow us to use existing properties in DT and
of_get_regulation_constraints() would provide us those limits and flag
that this code path is valid.

>> Having drms_uA_update() request an appropriate mode for the given load
>> and then calling set_mode directly (the current implementation) gives us
>> a single point of entry to the regulator drivers related to setting
>> modes (regulator_set_mode and drms_uA_update calls set_mode). But seen
>> from a consumer there's no consistency; the last call to
>> regulator_set_mode() and regulator_set_optimum_mode() will win.
>
> That's fine, consumers shouldn't be using both simultaneously anyway.
> If a consumer is actually setting modes actively at runtime by name it
> needs to be fairly closely tied to a specific system and regulator so
> it's not clear if there's much use case anyway.
>

Indeed, as there's no MAX() or similar of the modes requested that
seems to be a sure way to get into problems otherwise.

>> I think this covers your concern about patch 3-7 as well, please let me
>> know what you think.
>
> Possibly.

Well, my question is still there:

Unless we replace the get_optimum_mode()/set_mode() pair with
notify_load() the driver API logic will become confusing; so for the
regulators that to day implement that combo I think we need patch 3-7
as well.

Regards,
Bjorn
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