Subject: [Linaro-acpi] [PATCH v7 04/17] ARM64 / ACPI: Introduce early_param for "acpi" and pass acpi=force to enable ACPI

From: [email-masked] (Jon Masters)
Date: Thu, 29 Jan 2015 13:44:36 -0500

On 01/29/2015 01:34 PM, Timur Tabi wrote:
> On 01/29/2015 12:28 PM, Ard Biesheuvel wrote:
>> The UEFI stub in the kernel uses the DTB file format (FDT) to pass
>> information about the UEFI memory map and system table to the kernel.
>> It does so even if there is no device tree that describes the
>> platform. In this case, the file only contains a /chosen DT node, and
>> nothing else, and it is up to the kernel to figure out that it can ask
>> UEFI for a set of ACPI tables that it can use instead to configure the
>> system. Otherwise, the /chosen node properties are added to a device
>> tree that contains the full platform description.
>>
>> The problem is that we have to decide how to distinguish a
>> conventional device tree DTB from a DTB that only exists to
>> communicate the UEFI entry points.
> 
> Ah, that's exactly what I'm seeing.  The UEFI stub in our kernel 
> generates a DTB, and therefore I always need to put acpi=force on our 
> kernel command line.

I expect some of the distros to patch ACPI always enabled. So from my
point of view this affects only those wanting to follow upstream.

Jon.