linux-kernel - Re: [PATCH v2 0/3] add fwnode support to reset subsystem

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Date:   Tue, 5 Apr 2022 09:24:34 +0200
From:   Clément Léger <clement.leger@...tlin.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Frank Rowand <frowand.list@...il.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        UNGLinuxDriver@...rochip.com,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Allan Nielsen <allan.nielsen@...rochip.com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/3] add fwnode support to reset subsystem

Le Mon, 4 Apr 2022 12:41:37 -0500,
Rob Herring <robh@...nel.org> a écrit :

> On Thu, Mar 24, 2022 at 03:12:34PM +0100, Clément Léger wrote:
> > This series is part of a larger series which aims at adding fwnode
> > support in multiple subsystems [1]. The goal of this series was to
> > add support for software node in various subsystem but in a first
> > time only the fwnode support had gained consensus and will be added
> > to multiple subsystems.  
> 
> The goal is describing a solution. What is the problem?
> 
> What's the scenario where you have a reset provider not described by 
> firmware providing resets to devices (consumers) also not described by 
> firmware.

Hi Rob, there was a link attached to this series since there was a
previous one that was sent which described the problem. Here is a link
to the same thread but to a specific message which clarifies the
problem and the solutions that were mentionned by other maintainers
(ACPI overlays, DT overlays, software nodes and so on):

https://lore.kernel.org/netdev/20220224154040.2633a4e4@fixe.home/

> 
> > For the moment ACPI node support is excluded from the fwnode support
> > to avoid creating an unspecified ACPI reset device description. With
> > these modifications, both driver that uses the fwnode_ API or the of_
> > API to register the reset controller will be usable by consumer
> > whatever the type of node that is used.  
> 
> Good, because controlling reset lines directly isn't how the ACPI device 
> model works AFAIK.

This was based on Mark Brown feedback.

> 
> > One question raised by this series is that I'm not sure if all reset
> > drivers should be modified to use the new fwnode support or keep the
> > existing device-tree support. Maintainer advice on that particular
> > question will be welcome.  
> 
> That would be pointless churn IMO. Why do we need to convert drivers 
> which the vast majority will never use anything but DT?

To have a single interface to maintain and to remove duplicated fields
(of_node, fwnode, fwnode_xlate, of_xlate) from reset controller struct.


-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com