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

[Grant Likely]

On Wed, Feb 9, 2011 at 9:55 AM, Rob Herring <robherring2 at gmail.com> wrote:
> Grant,
>
> On 02/09/2011 08:02 AM, Rob Herring wrote:
>>
>> 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;
>
> Actually, this needs to be:
>
> #ifdef CONFIG_OF
>        if (of_device_is_compatible(pdev->dev.of_node, "arm,pmu"))
>                type = ARM_PMU_DEVICE_CPU;
> #endif
>
> Seems fixing the struct device conditional is just the tip of the iceberg.
> Should we do empty functions for all driver accessed OF functions?

Usually all of the dt parsing code can be shuffled off into another
function that can be #ifdef/#else/#endif away, but there is always a
few functions that need to have empty implementations when CONFIG_OF
is disabled.  I prefer to take it on a case-by-case basis.

The #ifdef around dev->of_node is going away in 2.6.39

g.