Re: [Linaro-acpi] [RFC] ACPI on arm64 TODO List

Jon Masters
2014-12-18T05:04:27Z

On 12/16/14, 7:37 PM, Al Stone wrote:
> On 12/16/2014 08:48 AM, Mark Rutland wrote:

>> I am rather concerned about the relationship between items described
>> with _DSD and ACPI's existing device model. Describing the relationship
>> between devices and their input clocks, regulators, and so on defeats
>> much of the benefit ACPI is marketed as providing w.r.t. abstraction of
>> the underlying platform (and as Arnd mentioned above, that's not the
>> kind of platform we want to support with ACPI).
>
> My belief is that all those things should be set up into a known good
> state by UEFI on initial boot.

Correct. There should never be a situation in which any clocks are
explicitly exposed in the DSDT. Clock state should be set as a side
effect of calling ACPI methods to transition device state. _DSD is
intended to implement simple additions to the core spec, such as
metadata describing the MAC address, interface type, and PHY on a
network device. But it should never be used to expose clock nets.

I've spoken with nearly everyone building a 64-bit ARM server using ACPI
and in nearly every case also reviewed their tables. Nobody is going to
be so foolish on day one. The trick to some of the ongoing
discussion/planning is to ensure that guidance prevents mistakes later.

Jon.