linux-kernel - Re: [PATCH 02/48] ARM: at91: Document new TCB bindings

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Message-ID: <20160621202800.GB22435@rob-hp-laptop>
Date:	Tue, 21 Jun 2016 15:28:00 -0500
From:	Rob Herring <robh@...nel.org>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 02/48] ARM: at91: Document new TCB bindings

On Wed, Jun 15, 2016 at 09:29:55AM +0200, Boris Brezillon wrote:
> On Tue, 14 Jun 2016 16:47:37 -0500
> Rob Herring <robh@...nel.org> wrote:
> 
> > On Sat, Jun 11, 2016 at 12:03:05AM +0200, Alexandre Belloni wrote:
> > > The current binding for the TCB is not flexible enough for some use cases
> > > and prevents proper utilization of all the channels.
> > > 
> > > Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> > > Cc: Thierry Reding <thierry.reding@...il.com>
> > > Cc: linux-pwm@...r.kernel.org
> > > Cc: Rob Herring <robh+dt@...nel.org>
> > > Cc: devicetree@...r.kernel.org
> > > Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> > > ---
> > >  .../devicetree/bindings/arm/atmel-at91.txt         | 32 -----------
> > >  .../devicetree/bindings/mfd/atmel-tcb.txt          | 62 ++++++++++++++++++++++
> > >  .../devicetree/bindings/pwm/atmel-tcb-pwm.txt      | 12 +++--
> > >  3 files changed, 69 insertions(+), 37 deletions(-)
> > >  create mode 100644 Documentation/devicetree/bindings/mfd/atmel-tcb.txt  
> > 
> > [...]


> > > diff --git a/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > > index 8031148bcf85..ab8fbd5ba184 100644
> > > --- a/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > > +++ b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > > @@ -2,15 +2,17 @@ Atmel TCB PWM controller
> > >  
> > >  Required properties:
> > >  - compatible: should be "atmel,tcb-pwm"
> > > +- reg: tcb channel to use. Each channel can export 2 PWMs  
> > 
> > Is there a difference in channels? If not, then this compatible should 
> > go.
> 
> This one I don't understand.
> The TCB (Timer Counter Block) is an MFD containing 3 Timer Counter
> devices. Each of these devices (also called channels) can be assigned a
> specific mode:
> - timer mode (free-running of programmable)
> - waveform generator mode (IOW, a PWM)
> - capture mode (an IIO device, but we don't have any driver for that
>   right now)
> 
> So each sub-device of the TCB is represented as a sub-node with its own
> compatible. Is there a problem with that?

Missed this in my first reply. I guess for purposes of referencing pwm 
from other nodes this is okay.

Rob