linux-kernel - Re: [PATCH v5 01/16] dt-bindings: regulator: Document ROHM BD71282 regulator bindings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 29 Nov 2019 12:09:25 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
Cc:     "corbet@....net" <corbet@....net>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "hofrat@...dl.org" <hofrat@...dl.org>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "dmurphy@...com" <dmurphy@...com>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "jeffrey.t.kirsher@...el.com" <jeffrey.t.kirsher@...el.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "mchehab+samsung@...nel.org" <mchehab+samsung@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "jacek.anaszewski@...il.com" <jacek.anaszewski@...il.com>,
        "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "pavel@....cz" <pavel@....cz>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "phil.edworthy@...esas.com" <phil.edworthy@...esas.com>
Subject: Re: [PATCH v5 01/16] dt-bindings: regulator: Document ROHM BD71282
 regulator bindings

On Fri, Nov 29, 2019 at 07:48:13AM +0000, Vaittinen, Matti wrote:
> On Tue, 2019-11-19 at 19:36 +0000, Mark Brown wrote:

> > The driver interface was added in "regulator: add PM suspend and
> > resume
> > hooks".

> I looked through the set but didn't spot any new interface towards the
> regulator driver (which accesses the HW). I saw interface towards
> regulator consumer driver which can be used to set the constrains
> though.

The regulator driver has a bunch fo set_suspend_ operations.

> Specifically, I don't see voltage setting callback for different run-
> modes. Nor do I see voltage setting (or differentiation) of more than
> one suspend state.

set_suspend_voltage.

> To explain it further - my assumption is that the BD71828 'run-levels'
> (RUN0, ... RUN3) could be mapped to regulator modes
> REGULATOR_MODE_FAST, REGULATOR_MODE_NORMAL, REGULATOR_MODE_IDLE and 
> REGULATOR_MODE_STANDBY. But regulators which are controlled by these

That doesn't make sense at all, the modes affect the quality of
regulation not the voltage that is set.

> run-levels, can't be individually controlled. If state for one is
> changed, the state is changed for all of them. The DVS bucks 1,2,6 and

We don't really have anything that'd only work for group configuration
except for the suspend modes.

> > Ah, that's actually better.  It opens up possiblities for making use
> > of
> > the feature without encoding voltages in DT.  For example, you can
> > cache
> > the last however many voltages that were set and jump quickly to them
> > or
> > do something like put the top of the constraints in to help with
> > governors like ondemand.  I'd recommend trying for something like
> > that
> > rather than encoding in DT, it'll probably be more robust with things
> > like cpufreq changing.

> I wish I was working with the full product so that I could see and
> learn a proper example on how the cpufreq actually uses these
> interfaces :) I'd really like to understand this much better. Maybe
> this could be a topic for you to present in some Linux conference ;)
> Just please ping me when you are doing that and I'll be listening there
> for sure ;)

The cpufreq code is all there in kernel - drivers/cpufreq.  I can't
remember if Android still has a custom governor in their trees but it
doesn't really make much difference in terms of how it interacts with
the regulator drivers.

> Anyways, my idea was to set the inital voltage values for these states
> via DT - but allow the voltages to be changed at run-time too (I guess
> this idea is visible in the patch 12).

It'd be much better if you could avoid putting the voltages in the
binding if they're not strictly required.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)