[PATCH] drivers: CCI: add ARM CCI PMU support

[Kumar Gala]

On Aug 15, 2013, at 4:10 AM, Punit Agrawal wrote:

> Hi Kumar,
> 
> Thanks for a review of the bindings.
> 
> On 14/08/13 22:03, Kumar Gala wrote:
>> 
>> On Jul 23, 2013, at 4:19 AM, Punit Agrawal wrote:
>> 
>>> The CCI PMU can profile bus transactions at the master and slave
>>> interfaces of the CCI. The PMU can be used to observe an aggregated view
>>> of the bus traffic between the various components connected to the CCI.
>>> 
>>> Extend the existing CCI driver to support the PMU by registering a perf
>>> backend for it.
>>> 
>>> Document the device tree binding to describe the CCI PMU.
>>> 
>>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
>>> Cc: Nicolas Pitre <nico at linaro.org>
>>> Cc: Dave Martin <dave.martin at linaro.org>
>>> Cc: Rob Herring <rob.herring at calxeda.com>
>>> Cc: Will Deacon <will.deacon at arm.com>
>>> Signed-off-by: Punit Agrawal <punit.agrawal at arm.com>
>>> Reviewed-by: Will Deacon <will.deacon at arm.com>
>>> ---
>>> Documentation/devicetree/bindings/arm/cci.txt |   38 ++
>>> drivers/bus/arm-cci.c                         |  642 +++++++++++++++++++++++++
>>> 2 files changed, 680 insertions(+)
>>> 
>>> diff --git a/Documentation/devicetree/bindings/arm/cci.txt b/Documentation/devicetree/bindings/arm/cci.txt
>>> index 92d36e2..5bc95e5 100644
>>> --- a/Documentation/devicetree/bindings/arm/cci.txt
>>> +++ b/Documentation/devicetree/bindings/arm/cci.txt
>>> @@ -79,6 +79,34 @@ specific to ARM.
>>> 				    corresponding interface programming
>>> 				    registers.
>>> 
>>> +	- CCI PMU node
>>> +
>>> +		Node name must be "pmu".
>>> +		Parent node must be CCI interconnect node.
>>> +
>>> +		A CCI pmu node must contain the following properties:
>>> +
>>> +		- compatible
>>> +			Usage: required
>>> +			Value type: <string>
>>> +			Definition: must be set to one of
>>> +				    "arm,cci-400-pmu"
>>> +				    "arm,cci-400-pmu,rev0"
>>> +				    "arm,cci-400-pmu,rev1"
>> 
>> Do you really mean only one?  Seems like ""arm,cci-400-pmu,rev0", "arm,cci-400-pmu" would be valid.
>> 
> 
> Hmm... yes both would be valid. But...
> 
> The event numbering scheme changed between Rev 0 and Rev 1 of the CCI. If the revision is specified then it is used to get the event ranges to validate the events. If not, i.e., "arm,cci-400-pmu" is used, then the driver tries to find the the revision by reading the peripheral id registers.
> 
> I was trying to make the bindings robust in the face of change in behaviour between different revisons of the IP.

If there is a periph id register why bother with the device tree having different version info in it?

- k

-- 
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