Re: [PATCH v6 17/18] ARM: sun4i: dt: Add ahci / sata support

[Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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Hi,

On 03/03/2014 10:33 AM, Maxime Ripard wrote:
> Hi Hans,
> 
> On Sat, Feb 22, 2014 at 08:10:54PM +0100, Hans de Goede wrote:
>>>>> Since IIRC we have pretty much the same needs for the USB, can't we just drop the SATA specific mention and use it as the common DTSI for the usual regulators?
>>>> 
>>>> On most boards with sata, there will also be 1 or 2 usb regulators, so we need differently named regulator nodes for all 3 of ahci, usb1 and usb2 vbus. On some boards how ever we may only need the usb regulators.
>>> 
>>> Yes, obviously...
>>> 
>>>> So if you look in my current personal sunxi-devel tree you will see separate dtsi files for both ahci and usb regulators,
>>> 
>>> And this is precisely what I don't understand. Why do you *need* different DTSI files. If there's common regulators, that are used on most boards, fine, create a common regulators files. But why do you have to create a DTSI to define only one regulator.
>>> 
>>>> another advantage of having these separate is that the gpio controlling the regulator can be pre-populated with the reference design gpio which is used in most boards, so that the ahci specific code in the dts becomes only the ahci: sata@... node.
>>> 
>>> I understand very well the advantages of what having a reference regulators bring. What I don't understand is the benefits of having "topics" regulators DTSI.
>> 
>> Ok, so let me try to explain:
>> 
>> With topics regulator files, the ahci bits look something like this for a board using the reference design gpio:
>> 
>> /include/ "sunxi-ahci-reg.dtsi"
>> 
>> ...
>> 
>> ahci: sata@01c18000 { target-supply = <&reg_ahci_5v>; status = "okay"; };
>> 
>> If we put all regulators in one file, then the ahci regulator cannot be enabled (so it will have status = "disabled) by default since most boards don't have it, so things would change into:
>> 
>> /include/ "sunxi-common-regulators.dtsi"
>> 
>> ...
>> 
>> ahci: sata@01c18000 { target-supply = <&reg_ahci_5v>; status = "okay"; };
>> 
>> ...
>> 
>> reg_ahci_5v: ahci-5v { status = "okay"; };
>> 
>> Notice the addition of the 2nd node. This is why I ended up doing 2 separate dtsi files for the ahci and for the usb regulators.
>> 
>> To me saying:
>> 
>> /include/ "sunxi-ahci-reg.dtsi"
>> 
>> Makes it clear to the reader that the board has a ahci target-supply regulator, so enabling it separately seems being overly verbose.
>> 
>> Of course of we change it to:
>> 
>> /include/ "sunxi-common-regulators.dtsi"
>> 
>> Then the verbosity / explicit enabling of various regulators becomes a good thing, as it is not directly clear what the include does.
>> 
>> But if we do this, then for many boards we end up replacing:
>> 
>> /include/ "sunxi-ahci-reg.dtsi" /include/ "sun4i-a10-usb-vbus-reg.dtsi"
>> 
>> With:
>> 
>> /include/ "sunxi-common-regulators.dtsi"
>> 
>> reg_ahci_5v: ahci-5v { status = "okay"; };
>> 
>> reg_usb1_vbus: usb1-vbus { status = "okay"; };
>> 
>> reg_usb2_vbus: usb2-vbus { status = "okay"; };
>> 
>> I prefer the shorter version, but I can completely understand if you prefer the slightly more verbose version, this would also get rid of having different usb regulator dtsi files for sun4i / sun5i (as sun5i only has 1 usb host).
>> 
>> I hope this helps explain my reasoning, as said I'm fine with either way, if you want to change over to a single file + explicit enabling, let me know and I'll respin the ahci dts patches.  Note I'm going on vacation for a week starting Monday, so you likely won't get a new version until next weekend.
> 
> Yes, I strongly prefer the second case. That allows to have a good-enough degree of factorisation, while not having anything happening behind the scenes.

Good, note I've already assumed as much and send a new series
which already has moved over to 1 common regulators dtsi,
with all regulators disabled by default + explicit enabling
in the board dts files.

Regards,

Hans
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