[U-Boot] ACPI tables for Edison: advice needed

[Andy Shevchenko]

On Tue, Aug 29, 2017 at 12:34 PM, Bin Meng <bmeng.cn at gmail.com> wrote:
> On Tue, Aug 29, 2017 at 5:10 PM, Andy Shevchenko
> <andy.shevchenko at gmail.com> wrote:
>> On Tue, Aug 29, 2017 at 7:49 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>> On Tue, Aug 29, 2017 at 1:12 AM, Andy Shevchenko
>>> <andy.shevchenko at gmail.com> wrote:

>>>> *) LInux kernel (vanilla) is not ready for this change. It means in
>>>> all above cases there will be neither new config file (like
>>>> edison_acpi_defconfig) nor modification to the existing one (of
>>>> course!). The stuff is highly experimental now.
>>
>> (Just to clarify, configurations mentioned in above remark are related
>> solely for U-Boot)
>>
>>> Does Linux kernel need to do anything to support ACPI on Intel Edison?
>>
>> There are few groups of problems:
>> 1. Edison has an _ugly_ SFI which means the kernel has many platform
>> drivers, like board code, that enumerated from hard coded platform
>> data.
>> 2. ACPI is kinda artificial on Edison, that's why it uses HW reduced
>> bit set, and kernel, surprise, surprise, has bugs in that code.
>
> Ah, surprised! But I can imagine that is maybe due to there is no HW
> reduced platform available to be tested with Linux kernel yet.

No, ASuS T100TA is the one, but the hardware OTOH has legacy devices
and ACPI HW (or at least doesn't behave weird when accessing to ACPI
HW registers).
So, basically this seems to be _the_ HW reduced platform Linux kernel
has been tested on.

>> 3. Drivers for devices that located on extension boards like
>> Edison/Arduino are not ready to be enumerated via ACPI (this one
>> optional and can be done later).

>> 4. There is lack of framework such as pin control ACPI (glue layer
>> between ACPICA and pin control which I'm working on as a main task),
>
> Does drivers/pinctrl/intel/ (in kernel tree) not apply to this? I see
> there are ACPI drivers, but maybe you are saying ACPI-defined native
> support for GPIO (ie: using ASL to describe pin)?

Native support for _pin control_ (yes, in terms of ACPI r6.2). Native
GPIO support (ACPI r5.0 or even earlier?) is in Linux kernel already
for quite a few releases.

>> though in the sense of Linux kernel it affect entire x86 world.
>>
>>> My understanding is that ACPI is a standard spec, and as long as our
>>> U-Boot implementation matches the spec, Linux kernel can support it
>>> out of the box.
>>
>> That's correct, though see above.
>>
>> P.S. There is a wiki page that I'm filling with my progress wrt topic:
>> https://edison.internet-share.com/wiki/ACPI
>
> Thanks for the link! It's amazing job you have done so far.


-- 
With Best Regards,
Andy Shevchenko