linux-kernel - Re: [PATCH v1 0/5] power: domain: Add driver for a PM domain provider which controls

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Date:   Wed, 15 Jun 2022 20:12:26 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        "max.oss.09@...il.com" <max.oss.09@...il.com>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
        "linux-imx@....com" <linux-imx@....com>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
        "biju.das.jz@...renesas.com" <biju.das.jz@...renesas.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "khilman@...nel.org" <khilman@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        Andrejs Cainikovs <andrejs.cainikovs@...adex.com>,
        "will@...nel.org" <will@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "festevam@...il.com" <festevam@...il.com>,
        Max Krummenacher <max.krummenacher@...adex.com>
Subject: Re: [PATCH v1 0/5] power: domain: Add driver for a PM domain
 provider which controls

On Wed, Jun 15, 2022 at 07:24:50PM +0100, Robin Murphy wrote:

> Multiple consumers sharing a voltage rail provided by a single regulator is
> so standard and well-supported that it barely seems worth pointing out, but
> for the avoidance of doubt I shall. Adding a new non-standard way to hide a
> specific subset of regulator functionality behind behind a magic driver
> because it seems like slightly less work than handling it the well-known
> established way sounds like a great recipe for technical debt and future
> compatibility headaches. What if down the line you end up with a situation
> where if device A is suspended, devices B and C are happy to save some power
> by running the "domain" at a lower voltage? Do we stubbornly start
> duplicating more of the regulator framework in the magic power domain
> driver, or is that the point where we have to switch all the consumers to
> explicit supplies, and get to regret having "saved" that effort in the first
> place...

We also loose the runtime validation that the supplies being described
in the DT correspond to the hardware in any meaningful way which would
also make it harder to transition to explicit control of the supplies
further down the line.  

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