linux-kernel - Re: [PATCH 3/4] dt-bindings: power: reset: Add regmap support to the SYSCON reboot-mode bindings

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Message-ID: <20200416212842.GA18756@bogus>
Date:   Thu, 16 Apr 2020 16:28:42 -0500
From:   Rob Herring <robh@...nel.org>
To:     Sergey Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Sebastian Reichel <sre@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] dt-bindings: power: reset: Add regmap support to the
 SYSCON reboot-mode bindings

On Thu, Apr 16, 2020 at 10:56:20PM +0300, Sergey Semin wrote:
> Rob,
> Any comment on my suggestion below?
> 
> Regards,
> -Sergey
> 
> On Tue, Mar 31, 2020 at 10:50:53PM +0300, Sergey Semin wrote:
> > On Wed, Mar 18, 2020 at 05:14:25PM -0600, Rob Herring wrote:
> > > On Fri, Mar 13, 2020 at 7:03 AM Sergey Semin
> > > <Sergey.Semin@...kalelectronics.ru> wrote:
> > > >
> > > > On Thu, Mar 12, 2020 at 04:14:38PM -0500, Rob Herring wrote:
> > > > > On Fri, Mar 06, 2020 at 04:03:40PM +0300, Sergey.Semin@...kalelectronics.ru wrote:
> > > > > > From: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > > > > >
> > > > > > Optional regmap property will be used to refer to a syscon-controller
> > > > > > having a reboot tolerant register mapped.
> > > > >
> > > > > NAK. It should simply be a child node of the 'syscon-controller'.
> > > >
> > > > Hm, It's dilemma. The driver maintainer said ack, while you disagree.)
> > > > So the code change will be merged while the doc-part won't? Lets discuss then
> > > > to settle the issue.
> > > >
> > > > Why 'syscon-reboot' can be out of syscon-controller node, while
> > > > 'syscon-reboot-mode' can't?
> > > 
> > > Look at the history and you will see one was reviewed by DT
> > > maintainers and one wasn't.
> > > 
> > > > They both belong to the same usecase: save
> > > > cause id and reboot. So having similar properties-set and declaring their
> > > > nodes someplace nearby is natural.
> > > 
> > > Which is what I'm asking for. Where else in the tree does it make
> > > sense to locate the 'syscon-reboot-mode' node? Locate nodes where they
> > > logically belong.
> > > 
> > > > According to the driver 'syscon-reboot'
> > > > can't lack the regmap property because it's mandatory, while here you refuse
> > > > to have even optional support. Additionally in most of the cases the
> > > > 'syscon-reboot' nodes aren't declared as a child of a system controller
> > > > node. Why 'syscon-reboot-mode' can't work in a similar way?
> > > 
> > > There's plenty of bad or "don't follow current best practice" examples
> > > in the tree for all sorts of things. That is not a reason for doing
> > > something in a new binding or adding to an existing one.
> > > 
> > > Rob
> > 
> > Alright. I see your point. What about I'd provide a sort of opposite
> > implementation? I could make the "regmap"-phandle reference being optional
> > in the !"syscon-reboot"! driver instead of adding the regmap-property
> > support to the "syscon-reboot-mode" driver. So if regmap property isn't
> > defined in the "syscon-reboot"-compatible node, the driver will try to
> > get a syscon regmap from the parental node as it's done in the
> > "syscon-reboot-mode" driver.

That seems fine.

> > Seeing you think that regmap-property-based design is a bad practice in
> > this case, I also could mark the property as deprecated in the "syscon-reboot"
> > dt schema and print a warning from the "syscon-reboot" driver if one is defined.

Depends on how many platforms will start getting warnings. I think just 
marking deprecated is enough.

Rob