[PATCH 1/3] ARM: pmu: add OF probing support

[robherring2@gmail.com (Rob Herring)]

Mark,

On 06/08/2011 10:54 AM, Mark Rutland wrote:
> Hi,
>
>>   static int __devinit pmu_device_probe(struct platform_device *pdev)
>>   {
>> +	enum arm_pmu_type type = pdev->id;
>>
>> -	if (pdev->id<  0 || pdev->id>= ARM_NUM_PMU_DEVICES) {
>> +	if (pdev->dev.of_node)
>> +		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[pdev->id])
>> +	if (pmu_devices[type])
>>   		pr_warning("registering new PMU device type %d overwrites "
>> -				"previous registration!\n", pdev->id);
>> +				"previous registration!\n", type);
>>   	else
>>   		pr_info("registered new PMU device of type %d\n",
>> -				pdev->id);
>> +				type);
>>
>> -	pmu_devices[pdev->id] = pdev;
>> +	pmu_devices[type] = pdev;
>>   	return 0;
>>   }
>
> I don't think this is the best way to handle the type when we've got an FDT
> description:
>
> * release_pmu hasn't been updated to match the type logic here, so it might do
>    anything when handed a platform_device initialised by FDT code.
>
> * the warning message for an invalid registration still uses pdev->id rather
>    than type. This can't currently be reached when the PMU was handed to us via
>    FDT, but it may confuse refactoring later on.
>
> * If we want to add a new PMU type, we'll have to add more logic to
>    pmu_device_probe. Given that work is going on to add support for system PMUs,
>    this doesn't seem particularly brilliant.
>
>> +static struct of_device_id pmu_device_ids[] = {
>> +	{ .compatible = "arm,cortex-a9-pmu" },
>> +	{ .compatible = "arm,cortex-a8-pmu" },
>> +	{ .compatible = "arm,arm1136-pmu" },
>> +	{ .compatible = "arm,arm1176-pmu" },
>> +	{},
>> +};
>> +
>>   static struct platform_driver pmu_driver = {
>>   	.driver		= {
>>   		.name	= "arm-pmu",
>> +		.of_match_table = pmu_device_ids,
>>   	},
>>   	.probe		= pmu_device_probe,
>>   };
>
> This all seems fine for handling CPU PMUs.
>
> I think that a better strategy would be to separate the type logic from the
> registration. I have a patch for this:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-June/052455.html
>
> With it, you won't need to change pmu_device_probe, and adding FDT support
> should just be a matter of adding the of_match_table.
>

Okay. I'll rebase mine on top of your changes.

Rob