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

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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.

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