linux-kernel - RE: [PATCH v2 2/4] mfd: Add RZ/V2M PWC core driver

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]

Message-ID: <TYWPR01MB8775DB97CD956756C7224440C2F49@TYWPR01MB8775.jpnprd01.prod.outlook.com>
Date:   Tue, 3 Jan 2023 15:00:06 +0000
From:   Fabrizio Castro <fabrizio.castro.jz@...esas.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Lee Jones <lee@...nel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo@...ndi.org>
Subject: RE: [PATCH v2 2/4] mfd: Add RZ/V2M PWC core driver

Hi Geert,

Thank you for your feedback!

> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 03 January 2023 12:10
> Subject: Re: [PATCH v2 2/4] mfd: Add RZ/V2M PWC core driver
> 
> Hi Fabrizio,
> 
> On Tue, Jan 3, 2023 at 1:05 PM Fabrizio Castro
> <fabrizio.castro.jz@...esas.com> wrote:
> > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > On Wed, Dec 21, 2022 at 10:09 PM Fabrizio Castro
> > > <fabrizio.castro.jz@...esas.com> wrote:
> > > > The External Power Sequence Controller (PWC) IP (found in the
> > > > RZ/V2M SoC) is a controller for external power supplies (regulators
> > > > and power switches), and it supports the following features: it
> > > > generates a power on/off sequence for external power supplies,
> > > > it generates an on/off sequence for the LPDDR4 core power supply
> > > > (LPVDD), it comes with General-Purpose Outputs, and it processes
> > > > key input signals.
> > >
> > > Thanks for your patch!
> > >
> > > > The PWC is basically a Multi-Function Device (MFD), its software
> > > > support comes with a core driver, and specialized drivers for
> > > > its specific features.
> > >
> > > I have to admit I'm not such a big fan of MFD.  In this driver,
> > > you are not even sharing resources in the MFD cells, just the mapped
> > > register base.  So I think you can easily save +100 LoC and reduce
> > > maintenance synchronization overhead across subsystems by just having
> > > a single non-MFD driver instead.
> > >
> > > Did you pick MFD because the PWC poweroff feature depends on board
> > > wiring, and thus is optional?
> >
> > I am not a big fan of MFD, either.
> > I picked MFD because we were not 100% sure of what the IP could do
> > when we started working on it.
> > I have received more information regarding the IP now (which I don't
> > have the liberty to discuss), I am still not 100% sure that's all
> > of it, but basically its support may require expansion later on.
> >
> > I liked the solution based on syscon and simple-mfd for several reasons,
> > but having dropped syscon and simple-mfd due to issues with the dt-
> bindings
> > I have moved on with a core driver to instantiate the required SW
> support.
> > We could of course move to a unified driver if that makes more sense?
> > If we were to move to unified driver, under which directory would you
> > suggest we put it?
> 
> As the GPIO part is larger than the poweroff part, I would put it under
> drivers/gpio/.  Although drivers/soc/renesas/ could be an option, too.

I'll try the unified approach then, under drivers/soc/renesas .

Thanks,
Fab 

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-
> m68k.org
> 
> In personal conversations with technical people, I call myself a hacker.
> But
> when I'm talking to journalists I just say "programmer" or something like
> that.
>                                 -- Linus Torvalds