linux-kernel - Re: [RFC 00/11] Add generic MFD i.MX mix and audiomix support

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Date:   Thu, 16 Apr 2020 13:06:03 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Abel Vesa <abel.vesa@....com>
Cc:     Rob Herring <robh@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Anson Huang <anson.huang@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        Peng Fan <peng.fan@....com>, Jacky Bai <ping.bai@....com>,
        NXP Linux Team <linux-imx@....com>,
        DTML <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [RFC 00/11] Add generic MFD i.MX mix and audiomix support

On Tue, Mar 3, 2020 at 10:04 AM Abel Vesa <abel.vesa@....com> wrote:
>
> The i.MX8MP has some new IPs called mixes. They are formed usually by some
> GPRs that can be split into different functionalities. The first example
> here is the audiomix which has dedicated registers that can be registered
> as a clock controller and some other registers that can be registered as
> a reset controller, plus some dedicated ones that will be registered as
> syscon and used by each dedicated audio IP.
>
> More mixes to be following the same structure are to come, like hdmimix,
> dispmix and mediamix. They will all be populated and registered by the MFD
> imx-mix generic driver.

Can you enumerate what functionality is in each one?

I'm not convinced that using an MFD driver is the best solution here,
compared to e.g. a clk driver with a few extra bits in it, if most of the
code for the child drivers ends up being for the clk subsystem.

Lee suggested maybe having a generic (platform independent) driver
for it, which may help here, as it would let others share the trivial
mfd portion.

Another option that we are using on several platforms today is to
have a single syscon node and have other drivers that reference
that one using a phandle to get at the regmap.

      Arnd