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

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Date:	Thu, 17 Mar 2016 18:06:10 +0000
From:	Robin Murphy <robin.murphy@....com>
To:	Rob Herring <robh@...nel.org>,
	Neil Armstrong <narmstrong@...libre.com>
Cc:	devicetree@...r.kernel.org, daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org, sudeep.holla@....com,
	rmk+kernel@....linux.org.uk, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 02/18] dt-bindings: timer: sp804: add timer-width
 property

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@...libre.com>
>> ---
>>   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 ;)

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

>
> Rob
>
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> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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