linux-kernel - Re: [PATCH v2 3/4] dt-bindings: mfd: Add Delta TN48M CPLD drivers bindings

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Date:   Mon, 31 May 2021 10:42:44 +0200
From:   Robert Marko <robert.marko@...tura.hr>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        bgolaszewski@...libre.com, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luka Perkov <luka.perkov@...tura.hr>, jmp@...phyte.org,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Donald Buczek <buczek@...gen.mpg.de>
Subject: Re: [PATCH v2 3/4] dt-bindings: mfd: Add Delta TN48M CPLD drivers bindings

On Wed, May 26, 2021 at 9:52 AM Lee Jones <lee.jones@...aro.org> wrote:
>
> On Tue, 25 May 2021, Robert Marko wrote:
>
> > On Tue, May 25, 2021 at 9:46 AM Lee Jones <lee.jones@...aro.org> wrote:
> > >
> > > On Mon, 24 May 2021, Rob Herring wrote:
> > >
> > > > On Mon, May 24, 2021 at 02:05:38PM +0200, Robert Marko wrote:
> > > > > Add binding documents for the Delta TN48M CPLD drivers.
> > > > >
> > > > > Signed-off-by: Robert Marko <robert.marko@...tura.hr>
> > > > > ---
> > > > > Changes in v2:
> > > > > * Implement MFD as a simple I2C MFD
> > > > > * Add GPIO bindings as separate
> > > >
> > > > I don't understand why this changed. This doesn't look like an MFD to
> > > > me. Make your binding complete if there are missing functions.
> > > > Otherwise, stick with what I already ok'ed.
> > >
> > > Right.  What else, besides GPIO, does this do?
> >
> > It currently does not do anything else as hwmon driver was essentially
> > NACK-ed for not exposing standard attributes.
>
> Once this provides more than GPIO capabilities i.e. becomes a proper
> Multi-Function Device, then it can use the MFD framework.  Until then,
> it's a GPIO device I'm afraid.
>
> Are you going to re-author the HWMON driver to conform?
hwmon cannot be reathored as it has no standard hwmon attributes.

>
> > The CPLD itself has PSU status-related information, bootstrap related
> > information,
> > various resets for the CPU-s, OOB ethernet PHY, information on the exact board
> > model it's running etc.
> >
> > PSU and model-related info stuff is gonna be exposed via a misc driver
> > in debugfs as
> > we have user-space SW depending on that.
> > I thought we agreed on that as v1 MFD driver was exposing those directly and
> > not doing anything else.
>
> Yes, we agreed that creating an MFD driver just to expose chip
> attributes was not an acceptable solution.
>
> > So I moved to use the simple I2C MFD driver, this is all modeled on the sl28cpld
> > which currently uses the same driver and then GPIO regmap as I do.
> >
> > Other stuff like the resets is probably gonna get exposed later when
> > it's required
> > to control it directly.
>
> In order for this driver to tick the MFD box, it's going to need more
> than one function.

Understood, would a debug driver count or I can expose the resets via
a reset driver
as we have a future use for them?

Regards,
Robert
>
> > > > >  .../bindings/gpio/delta,tn48m-gpio.yaml       | 42 ++++++++++
> > > > >  .../bindings/mfd/delta,tn48m-cpld.yaml        | 81 +++++++++++++++++++
> > > > >  2 files changed, 123 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/gpio/delta,tn48m-gpio.yaml
> > > > >  create mode 100644 Documentation/devicetree/bindings/mfd/delta,tn48m-cpld.yaml
> > >
> >
> >
> >
>
> --
> Lee Jones [李琼斯]
> Senior Technical Lead - Developer Services
> Linaro.org │ Open source software for Arm SoCs
> Follow Linaro: Facebook | Twitter | Blog



-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr