linux-kernel - Re: [RFC PATCH 2/2] mfd: syscon: allow reset control for syscon devices

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Message-ID: <0a8f144c920c63598a7283ad95975c3d5a7d7018.camel@codeconstruct.com.au>
Date:   Wed, 07 Dec 2022 17:28:39 +0800
From:   Jeremy Kerr <jk@...econstruct.com.au>
To:     Arnd Bergmann <arnd@...db.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [RFC PATCH 2/2] mfd: syscon: allow reset control for syscon
 devices

Hi Arnd,


> Hmm, it's clearly not doing what I was remembering it to do ;-)
> 
> Before 2014 commit bdb0066df96e ("mfd: syscon: Decouple syscon
> interface
> from platform devices"), it was supposed to be the same regmap in
> both cases, with the linked list being maintained to ensure we
> never get more than one instance for device_node.

Yep, that makes sense with your earlier suggestions.

> After this commit, I see that the platform_driver no longer matches
> syscon nodes from devicetree, but only those nodes that have
> platform_device.dev.name="syscon" and are created from board
> files. The only user of manually created syscon devices at the
> time was mach-clps711x, but that has been converted to DT
> a long time ago, so I don't even see anything using the
> platform_device at all.
> 
> This would in turn indicate that we can completely remove the
> platform_driver code, but I don't see how your RFC patch then
> had any effect because it wouldn't actually perform the
> reset for any devices in mainline kernels.

I've been changing a few things at once, it's entirely possible that my
testing is incorrect!

So, I'll add the reset controller linkage in just the DT-based code,
and leave the platform device as-is. And then make sure that I'm
getting the correct regmap <--> reset interactions :D

Cheers,


Jeremy