Re: [RFC PATCH] ARM: pmu: add OF match support

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Will,

On 02/09/2011 03:51 AM, Will Deacon wrote:
> Hi Rob,
>
>> Add OF match table to enable OF style driver binding. The dts entry is like
>> this:
>>
>> pmu {
>> 	compatible = "arm,pmu";
>> 	interrupts =<100 101>;
>> };
>>
>> The use of pdev->id as an index breaks with OF device binding. Change to use
>> a counter instead. If more than 1 pmu device is ever really supported, a
>> better solution to match users with particular pmu is probably needed.
>
> We will want to support multiple PMU devices in the near future but
> this is currently blocked on userspace issues. One such device would
> be the event counters on the PL310, which could be used to complement
> the CPU PMU on the Cortex-A9.
>
> I don't like the idea of a counter as it forces platforms to register
> their devices in a specific order. Is it possible to separate different
> types of PMU in the device tree and then have pmu.c work out what to do
> with them?

Yes, they are easily distinguished by the compatible strings. Adding a 
pmu_get function which returns the device based on a string or 
capabilities may be a better solution. If you had 2 pmu's of the same 
type, the current code would break.

In any case, how about this:

static int __devinit pmu_device_probe(struct platform_device *pdev)
{
	enum arm_pmu_type type = pdev->id;

	if (of_device_is_compatible(pdev->dev.of_node, "arm,pmu"))
		type = ARM_PMU_DEVICE_CPU;

	if (type < 0 || type >= ARM_NUM_PMU_DEVICES) {
		pr_warning("received registration request for unknown "
				"device %d\n", pdev->id);
		return -EINVAL;
	}

	if (pmu_devices[type])
		pr_warning("registering new PMU device type %d overwrites "
				"previous registration!\n", type);
	else
		pr_info("registered new PMU device of type %d\n",
				type);

	pmu_devices[type] = pdev;
	return 0;
}

Rob