On 10/01/2015 14:51, Hans de Goede wrote:
> Hi,
>
> On 10-01-15 12:17, Mark Brown wrote:
>> On Sat, Jan 10, 2015 at 11:20:13AM +0100, Hans de Goede wrote:
>>> On 09-01-15 18:11, Mark Brown wrote:
>>
>>>> Or if the supply is for the device at the other end of the link (which
>>>> is what it sounded like) then use that. This just sounds like the same
>>>> problem we have for all the enumerable buses in embedded systems where
>>>> we need to be able to understand that the device exists prior to it
>>>> being fully ready to appear in the system. Having the link/slot be a
>>>> device in Linux does indeed seem to be a common way people think about
>>>> doing this, it sounds like for this one it might be the most direct.
>>
>>> I think we should be careful to not think too much from an implementation
>>> pov here, the purpose of the devicetree description is to describe the hardware,
>>> as is.
>>
>> I don't think anyone is talking about changing the DT here, only the way
>> it's represented inside Linux.
>>
>>> sata0: sata-port@0 {
>>> reg = <0>;
>>> phys = <&sata_phy 0>;
>>> target-supply = <®_sata0>;
>>> };
>>>
>>> sata1: sata-port@1 {
>>> reg = <1>;
>>> phys = <&sata_phy 1>;
>>> target-supply = <®_sata1>;
>>> };
>>> };
>>
>>> Seems to match the hardware pretty exactly, and also matches how we've
>>> been describing similar devices with only one sata port + power plug sofar,
>>> so from a consistency pov it also is a good model.
>>
>> Right, I think that makes sense
>
> Good, as said I think getting the dt bit rights is the most important
> thing here. So if we agree that the above dt example looks sane, lets see
> how we can best implement that.
>
> > it also looks to me like these things
>> should be representable as devices within Linux.
>
> I guess we could manually instantiate platform devices for each of the
> subnodes which represent an sata port here, yes that should not be
> hard to do, it feels like a bit overkill though.
>
> So for our this should likely look something like this:
>
> if (IS_ENABLED(CONFIG_OF_ADDRESS) && dev->of_node) {
> for_each_child_of_node(dev->of_node, np) {
> pdev[i++] = of_platform_device_create(np, NULL, NULL);
> }
> }
>
> and then loop over the pdev[] array and get the regulator, and phy for each.
>
> I wonder if of_platform_device_create can deal with nodes with
> #size-cells = <0>; is 0 though, if it cannot maybe we need to teach it.
>
>>> So supporting this model requires having a regulator_get API which allows
>>> specifying which of_node to get the regulator from, e.g. the proposed
>>
>> It requires nothing of the sort.
>
> You're proposed solution of instantiating devices does more or less exactly
> what I say is required, it is a way to pass an of_node into regulator_get,
> but you're hiding the node inside dev->of_node. I can see the appeal in
> that.
>
>>> of_regulator_get function. I know you (Mark) do not like this, but all
>>> other subsystems have an of_foo_get function taking an of_node as argument,
>>> I do not see how the regulator subsys is so special that it cannot have one,
>>> and also notice that this is only a kernel internal API which we can always
>>> change later.
>>
>> Two things there. One is that mostly those APIs are legacy APIs from
>> before we made DT a first class citizen and generally they shouldn't be
>> used these days. The other is that at least for regulators we have
>> constant problems with people abusing the API in various ways, as a
>> result the API has a goal of not helping undesirable usage patterns in
>> order to help people spot problems. Having an API which makes it easy
>> create broken bindings means that it is much more likely that people
>> will do just that.
>
> Hmm I can see where you're coming from, and your proposed solution may
> also be useful for when we get similar boards requiring explicit regulator
> handling with the sata ports described in ACPI tables.
>
> Gregory, can you give the setup using per sata port devices a try, and
> see how that works out code wise ?
OK, I am taking care of it.
Thanks,
Gregory
--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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