[PATCH v5 18/18] Documentation: ACPI for ARM64

[G Gregory]

On 6 January 2015 at 11:20, Catalin Marinas <catalin.marinas at arm.com> wrote:
> On Mon, Jan 05, 2015 at 08:16:30PM +0000, Arnd Bergmann wrote:
>> On Monday 05 January 2015 13:13:02 Catalin Marinas wrote:
>> > > since passing no DT tables to OS but
>> > > acpi=force is missing is a corner case, we can do a follow up patch to
>> > > fix that, does it make sense?
>> >
>> > Not entirely. Why would no dtb and no acpi=force be a corner case? I
>> > thought this should be the default when only ACPI tables are passed, no
>> > need for an additional acpi=force argument.
>>
>> We don't really support the case of only ACPI tables for now. The expectation
>> is that you always have working DT support, at least for the next few years
>> as ACPI features are ramping up, and without acpi=force it should not try
>> to use ACPI at all.
>
> So if both DT and ACPI are present, just use DT unless acpi=force is
> passed. So far I think we agree but what I want to avoid is always
> mandating acpi=force even when the DT tables are missing (in the long
> run).
>
> Now, what's preventing a vendor firmware from providing only ACPI
> tables? Do we enforce it in some way (arm-acpi.txt, kernel warning etc.)
> that both DT and ACPI are supported, or at least that dts files are
> merged in the kernel first?
>
How do we tell the difference between a DT passed purely for booting purposes
ie a skeleton DT. And one which actually has hardware description as this needs
to be done before unpacking the DT.

Graeme