Re: [PATCH v2 02/18] dt-bindings: timer: sp804: add timer-width property

[Robin Murphy]

On 17/03/16 19:00, Rob Herring wrote:
> On Thu, Mar 17, 2016 at 1:06 PM, Robin Murphy <robin.murphy@xxxxxxx> wrote:
> > Hi Rob,
> >
> > On 17/03/16 17:09, Rob Herring wrote:
> > > On Wed, Mar 09, 2016 at 11:24:04AM +0100, Neil Armstrong wrote:
> > > > Add timer-width optional property to specify a different vendor
> > > > specific timer counter bit-width.
> > > >
> > > > Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> > > > ---
> > > >    Documentation/devicetree/bindings/timer/arm,sp804.txt | 2 ++
> > > >    1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/timer/arm,sp804.txt
> > > > b/Documentation/devicetree/bindings/timer/arm,sp804.txt
> > > > index 5cd8eee7..141e143 100644
> > > > --- a/Documentation/devicetree/bindings/timer/arm,sp804.txt
> > > > +++ b/Documentation/devicetree/bindings/timer/arm,sp804.txt
> > > > @@ -17,6 +17,8 @@ Optional properties:
> > > >    - arm,sp804-has-irq = <#>: In the case of only 1 timer irq line
> > > > connected, this
> > > >          specifies if the irq connection is for timer 1 or timer 2. A
> > > > value of 1
> > > >          or 2 should be used.
> > > > +- arm,timer-width: Should contain the width in number of bits of the
> > > > counter,
> > > > +       is considered by default 32 but can be changed for vendor
> > > > variants.
> > >
> > >
> > > That would not be an SP804 nor would the vendor be ARM in that case. So
> > > add a new compatible string for the vendor that decided to hack up ARM's
> > > IP block.
> >
> >
> > By all accounts this is some ancient reference design[1] which later evolved
> > _into_ the SP804, so that vendor would probably still be ARM ;)
>
> Right.
>
> > A separate compatible string would indeed make more sense, though. Both
> > semantically and in terms of letting the driver account for the differences
> > automatically.
> >
> > Robin.
> >
> > [1]:http://infocenter.arm.com/help/topic/com.arm.doc.ddi0170a/I350250.html
>
> Humm, same as integrator timers perhaps?

Having had a quick look, what the Integrator/AP manual describes 
certainly smells like the same basic block as the "AMBA Timer" - 16 bit 
counters and the same control register layout - albeit in a mutant 
triple-timer version with a bigger offset between each register set. 
Integrator/CP, on the other hand, looks much more SP804-like.

Robin.