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From: Doug Anderson <dianders@chromium.org>
To: David Collins <collinsd@codeaurora.org>
Cc: Mark Brown <broonie@kernel.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-arm-msm@vger.kernel.org,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	devicetree@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	Stephen Boyd <sboyd@kernel.org>
Subject: Re: [PATCH v4 1/2] regulator: dt-bindings: add QCOM RPMh regulator bindings
Date: Wed, 30 May 2018 17:34:43 -0700	[thread overview]
Message-ID: <CAD=FV=VNVE5ttNg+7xmgh-p1sFbCxCY1DJiri0JtHFax+zVsnA@mail.gmail.com> (raw)
In-Reply-To: <75088820-f20d-32ac-780a-5e7dacdf20ff@codeaurora.org>

Hi,

On Wed, May 30, 2018 at 4:39 PM, David Collins <collinsd@codeaurora.org> wrote:
> Consider the case of a regulator with physical 10 mA LPM max current. Say
> that modem and application processors each have a load on the regulator
> that draws 9 mA. If they each respect the 10 mA limit, then they'd each
> vote for LPM. The VRM block in RPMh hardware will aggregate these requests
> together using a max function which will result in the regulator being set
> to LPM, even though the total load is 18 mA (which would require high
> power mode (HPM)). To get around this corner case, a LPM max current of 1
> uA can be used for all LDO supplies that have non-application processor
> consumers. Thus, any non-zero regulator_set_load() current request will
> result in setting the regulator to HPM (which is always safe).

Is there any plan to change the way this works for future versions of RPMh?


> The second situation that needs board-level DRMS mode and current limit
> specification is SMPS regulator AUTO mode to PWM (HPM) mode switching.
> SMPS regulators should theoretically always be able to operate in AUTO
> mode as it switches automatically between PWM mode (which can provide the
> maximum current) and PFM mode (which supports lower current but has higher
> efficiency). However, there may be board/system issues that require
> switching to PWM mode for certain use cases as it has better load
> regulation (i.e. no PFM ripple for lower loads) and supports more
> aggressive load current steps (i.e. greater A/ns).
>
> If a Linux consumer requires the ability to force a given SMPS regulator
> from AUTO mode into PWM mode and that SMPS is shared by other Linux
> consumers (which may be the case, but at least must be guaranteed to work
> architecturally), then regulator_set_load() is the only option since it
> provides aggregation, where as regulator_set_mode() does not.
> regulator_set_load() can be utilized in this case by specifying AUTO mode
> and PWM mode as drms modes and specifying some particular AUTO mode
> maximum current (that is known by the consumer) in device tree.  The
> consumer can then call regulator_set_load() with the imposed AUTO mode
> limit + delta when PWM mode is required and a lower value when AUTO mode
> is sufficient.

Mark: I'm leaving this firmly in your hands.  I can see David's points
here.  I could even believe that some of this stuff could be board
specific where one board might have slightly different capacitors or
they might be placed differently and might need a higher power mode to
keep the signal clean.

-Doug

  reply	other threads:[~2018-05-31  0:34 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-23  2:43 [PATCH v4 0/2] regulator: add QCOM RPMh regulator driver David Collins
2018-05-23  2:43 ` [PATCH v4 1/2] regulator: dt-bindings: add QCOM RPMh regulator bindings David Collins
2018-05-23 16:22   ` Rob Herring
2018-05-30  5:23   ` Doug Anderson
2018-05-30 10:37     ` Mark Brown
2018-05-30 14:54       ` Doug Anderson
2018-05-30 15:50         ` Mark Brown
2018-05-30 16:12           ` Doug Anderson
2018-05-30 16:20             ` Mark Brown
2018-05-30 16:24               ` Doug Anderson
2018-05-30 23:39                 ` David Collins
2018-05-31  0:34                   ` Doug Anderson [this message]
2018-05-31  1:03                     ` David Collins
2018-05-31 11:48                   ` Mark Brown
2018-06-01 21:41                     ` David Collins
2018-05-23  2:43 ` [PATCH v4 2/2] regulator: add QCOM RPMh regulator driver David Collins
2018-05-30  5:32   ` Doug Anderson
2018-05-30 23:58     ` David Collins
2018-05-30 16:33 ` [PATCH v4 0/2] " Mark Brown
2018-05-31  0:11   ` David Collins
2018-05-31 10:38     ` Mark Brown

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