linux-kernel - Re: [PATCH 18/18] ipu3: Add driver for dummy INT3472 ACPI device

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Date:   Wed, 2 Dec 2020 17:08:58 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-media@...r.kernel.org, devel@...ica.org, rjw@...ysocki.net,
        lenb@...nel.org, gregkh@...uxfoundation.org,
        mika.westerberg@...ux.intel.com, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, wsa@...nel.org, yong.zhi@...el.com,
        bingbu.cao@...el.com, tian.shu.qiu@...el.com, mchehab@...nel.org,
        robert.moore@...el.com, erik.kaneda@...el.com, pmladek@...e.com,
        rostedt@...dmis.org, sergey.senozhatsky@...il.com,
        linux@...musvillemoes.dk, kieran.bingham+renesas@...asonboard.com,
        jacopo+renesas@...ndi.org,
        laurent.pinchart+renesas@...asonboard.com,
        jorhand@...ux.microsoft.com, kitakar@...il.com,
        heikki.krogerus@...ux.intel.com
Subject: Re: [PATCH 18/18] ipu3: Add driver for dummy INT3472 ACPI device

On Wed, Dec 02, 2020 at 02:42:28PM +0200, Laurent Pinchart wrote:
> On Wed, Dec 02, 2020 at 01:09:56PM +0200, Sakari Ailus wrote:
> > On Tue, Dec 01, 2020 at 08:37:58PM +0200, Laurent Pinchart wrote:

...

> I think we should consider ACPI to be a hack in the first place :-)

I feel that about DT (and all chaos around it) but it's not a topic here.

> > Could this be just one more platform device for each of the three cases (or
> > one for the two latter; I'm not quite sure yet)?
> 
> Using MFD for this seems a bit overkill to me. I won't care much as I
> won't maintain those drivers, but the current situation is complex
> enough, it was hard for me to understand how things worked. Adding yet
> another layer with another platform device won't make it any simpler.
> 
> If we want to split this in two, I'd rather have a tps68470 driver on
> one side, without ACPI op region support, but registering regulators,
> GPIOs and clocks (without using separate drivers and devices for these
> three features), and an INT3472 driver on the other side, with all the
> ACPI glue and hacks. The tps68470 code could possibly even be structured
> in such a way that it would be used as a library by the INT3472 driver
> instead of requiring a separate platform device.

I'm afraid TPS68470 is MFD in hardware and its representation in the MFD is
fine. What we need is to move IN3472 pieces out from it.

And I agree with your proposal in general.

> > The GPIO regulator case is relatively safe, but the real PMICs require
> > regulator voltage control as well as enabling and disabling the regulators.
> > That probably requires either schematics or checking the register values at
> > runtime on Windows (i.e. finding out which system you're dealing with, at
> > runtime).

-- 
With Best Regards,
Andy Shevchenko