linux-kernel - Re: [PATCH v3 09/10] arch: arm: boot: dts: Introduce HPE GXP Device tree

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Date:   Fri, 1 Apr 2022 18:30:26 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     "Hawkins, Nick" <nick.hawkins@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "Verdun, Jean-Marie" <verdun@....com>,
        Olof Johansson <olof@...om.net>,
        "soc@...nel.org" <soc@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 09/10] arch: arm: boot: dts: Introduce HPE GXP Device tree

On Fri, Apr 1, 2022 at 6:05 PM Hawkins, Nick <nick.hawkins@....com> wrote:
> > I don't think you can do this, if you are using the syscon regmap, you go through the regmap indirection rather than accessing the mmio register by virtual address, and this may result in some extra code in your driver, and a little runtime overhead.
>
> > If you prefer to avoid that, you can go back to having the timer node as the parent, but without being a syscon. In this case, the watchdog would be handled in one of these ways:
>
> > a) a child device gets created from the clocksource driver and bound to the
>     watchdog driver, which then uses a private interface between the clocksource
>     and the watchdog to access the registers
>
> > b) the clocksource driver itself registers as a watchdog driver, without
>     having a separate driver module
>
> > One thing to consider is whether the register range here contains any registers that may be used in another driver, e.g. a second timer, a PWM, or a clk controller. If not, you are fairly free to pick any of these approaches.
>
> I will try to use the b) approach everything in that range is timer or watchdog related. There is a second timer however there are no plans on using that. Should the combined code still live inside the driver/timer directory or should it be moved to mfd?

I would put it into drivers/clocksource/, I don't think drivers/mtd
would be any better,
but there is a chance that the clocksource maintainers don't want to
have the watchdog
code in their tree.

        Arnd