linux-kernel - Re: [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer

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Date:   Thu, 13 May 2021 15:43:27 -0500
From:   Rob Herring <robh@...nel.org>
To:     Sean Anderson <sean.anderson@...o.com>
Cc:     Linux PWM List <linux-pwm@...r.kernel.org>,
        devicetree@...r.kernel.org, Michal Simek <michal.simek@...inx.com>,
        Alvaro Gamez <alvaro.gamez@...ent.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer

On Thu, May 13, 2021 at 10:28 AM Sean Anderson <sean.anderson@...o.com> wrote:
>
>
>
> On 5/13/21 10:33 AM, Sean Anderson wrote:
>  >
>  >
>  > On 5/12/21 10:16 PM, Rob Herring wrote:
>  >  > On Tue, May 11, 2021 at 03:12:37PM -0400, Sean Anderson wrote:
>  >  >> This adds a binding for the Xilinx LogiCORE IP AXI Timer. This device is
>  >  >> a "soft" block, so it has many parameters which would not be
>  >  >> configurable in most hardware. This binding is usually automatically
>  >  >> generated by Xilinx's tools, so the names and values of some properties
>  >  >> must be kept as they are. Replacement properties have been provided for
>  >  >> new device trees.
>  >  >
>  >  > Because you have some tool generating properties is not a reason we have
>  >  > to accept them upstream.
>  >
>  > These properties are already in arch/microblaze/boot/dts/system.dts and
>  > in the devicetree supplied to Linux by qemu. Removing these properties
>  > will break existing setups, which I would like to avoid.

Already in use in upstream dts files is different than just
'automatically generated' by vendor tools.

>  >
>  >  > 'deprecated' is for what *we* have deprecated.
>  >
>  > Ok. I will remove that then.
>  >
>  >  >
>  >  > In this case, I don't really see the point in defining new properties
>  >  > just to have bool.
>  >
>  > I don't either, but it was requested, by Michal...
>
> Err, your comment on the original bindings was
>
>  > Can't all these be boolean?

With no other context, yes that's what I would ask. Now you've given
me some context, between using the existing ones and 2 sets of
properties to maintain, I choose the former.

> And Michal commented
>
>  > I think in this case you should described what it is used by current
>  > driver in Microblaze and these options are required. The rest are by
>  > design optional.
>  > If you want to change them to different value then current binding
>  > should be deprecated and have any transition time with code alignment.
>
> So that is what I tried to accomplish with this revision. I also tried
> allowing something like
>
>         xlnx,one-timer-only = <0>; /* two timers */
>         xlnx,one-timer-only = <1>; /* one timer  */
>         xlnx,one-timer-only; /* one timer */
>         /* property absent means two timers */
>
> but I was unable to figure out how to express this with json-schema. I
> don't think it's the best design either...

json-schema would certainly let you, but generally we don't want
properties to have more than 1 type.

Rob