Re: [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer

[Stephen Warren]

On 05/28/2013 03:25 PM, Jon Hunter wrote:
> 
> On 27/05/13 15:37, Afzal Mohammed wrote:
>> AM43x timer bindings.
>>
>> Signed-off-by: Afzal Mohammed <afzal@xxxxxx>
>> ---
>>  Documentation/devicetree/bindings/arm/omap/timer.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/omap/timer.txt b/Documentation/devicetree/bindings/arm/omap/timer.txt
>> index d02e27c..70cb398 100644
>> --- a/Documentation/devicetree/bindings/arm/omap/timer.txt
>> +++ b/Documentation/devicetree/bindings/arm/omap/timer.txt
>> @@ -14,6 +14,8 @@ Required properties:
>>  			ti,omap5430-timer (applicable to OMAP543x devices)
>>  			ti,am335x-timer	(applicable to AM335x devices)
>>  			ti,am335x-timer-1ms (applicable to AM335x devices)
>> +			"ti,am4372-timer-1ms", "ti,am335x-timer-1ms" for AM43x 1ms timer
>> +			"ti,am4372-timer", "ti,am335x-timer" for AM43x timers other than 1ms one
>>  
>>  - reg:			Contains timer register address range (base address and
>>  			length).
> 
> If you are adding more compatibility strings, then this implies that the
> AM43x timers are not 100% compatible with any other device listed (such
> as am335x or any omap device). That's fine but you should state that in
> the changelog. If the AM43x timer registers are 100% compatible with
> existing devices you should not add these.

I'm not sure that's true; .dts files should always include a compatible
value that describes the most specific model of the HW, plus any
baseline compatible value that the HW is compatible with. This allows
any required quirks/fixes/... to be applied for the specific HW model
later even if nobody knows right now they'll be needed. Hence, defining
new compatible values doesn't necessarily mean incompatible HW.

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