On 07/21/2014 02:09 PM, Thomas Petazzoni wrote:

Dear Arnd Bergmann,

On Mon, 21 Jul 2014 14:00:22 +0200, Arnd Bergmann wrote:

quoted

I don't know, it really depends on what the differences are between
the SoCs, and I haven't looked at them.

Using the compatible strings would make it work best if you have one
driver per variant, and then share some common code, as opposed to
having one shared driver with a number of exceptions.

If the differences are just a few parameters, it might be better
to encode those parameters in DT properties instead.

The differences are in the cpuidle states that are supported, see
patches "cpuidle: mvebu: add Armada 370 support" and "cpuidle: mvebu:
add Armada 38x support" in the series.

I honestly believe that since cpuidle functionality is not described in
the Device Tree and therefore probed using a statically defined
platform_device, the good way to pass these informations is to simply
use platform_data.

Ok, so for the record the cpuidle functionality described via DT is 
under discussion [1].

I understand you need several drivers for the different SoC because of 
the different latencies.

I admit passing an extra flag via the platform_data is a valid approach 
but I have been unifying the different drivers across the existing SoC 
and there is still a lot of things to do. So accepting this patch brings 
another way to discriminate the SoC variant I would like to avoid.

Due the different latencies, I don't think the DT property is enough and 
that may enter in conflict with Lorenzo's work.

So there are three solutions:

1. Pass the flag through the platform data, I am not really in favor of 
that as mentioned above

2. Use the compatible string like the cpuidle-big-little.c driver, but 
Arnd is not in favor of that

3. Register 3 platform drivers, in cpuidle-mvebu-v7.c, and let the 
registering of the cpuidle's platform device to enable the right one


[1] http://www.spinics.net/lists/arm-kernel/msg341541.html


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