On Mon, Jan 19, 2015 at 05:52:33PM +0000, Catalin Marinas wrote: > On Mon, Jan 19, 2015 at 04:59:47PM +0000, Jon Masters wrote: > > On 01/19/2015 10:13 AM, Grant Likely wrote: > > > On Mon, 19 Jan 2015 13:51:45 +0000 > > > , Catalin Marinas <catalin.mari...@arm.com> > > > wrote: > > >> On Mon, Jan 19, 2015 at 11:55:32AM +0000, Ard Biesheuvel wrote: > > >>> On 19 January 2015 at 11:42, Catalin Marinas <catalin.mari...@arm.com> > > >>> wrote: > > >>>> On Wed, Jan 14, 2015 at 03:04:52PM +0000, Hanjun Guo wrote: > > >>>>> From: Al Stone <al.st...@linaro.org> > > >>>>> > > >>>>> Introduce one early parameters "off" and "force" for "acpi", acpi=off > > >>>>> will be the default behavior for ARM64, so introduce acpi=force to > > >>>>> enable ACPI on ARM64. > > >>>>> > > >>>>> Disable ACPI before early parameters parsed, and enable it to pass > > >>>>> "acpi=force" if people want use ACPI on ARM64. This ensures DT be > > >>>>> the prefer one if ACPI table and DT both are provided at this moment. > > >>>> [...] > > >>>>> --- a/arch/arm64/kernel/setup.c > > >>>>> +++ b/arch/arm64/kernel/setup.c > > >>>>> @@ -62,6 +62,7 @@ > > >>>>> #include <asm/memblock.h> > > >>>>> #include <asm/psci.h> > > >>>>> #include <asm/efi.h> > > >>>>> +#include <asm/acpi.h> > > >>>>> > > >>>>> unsigned int processor_id; > > >>>>> EXPORT_SYMBOL(processor_id); > > >>>>> @@ -388,6 +389,8 @@ void __init setup_arch(char **cmdline_p) > > >>>>> early_fixmap_init(); > > >>>>> early_ioremap_init(); > > >>>>> > > >>>>> + disable_acpi(); > > >>>>> + > > >>>>> parse_early_param(); > > >>>>> > > >>>>> /* > > >>>> > > >>>> Did we get to any conclusion here? DT being the preferred one is fine > > >>>> when both DT and ACPI are present but do we still want the kernel to > > >>>> ignore ACPI altogether if DT is not present? It's a bit harder to > > >>>> detect > > >>>> the presence of DT at this point since the EFI_STUB added one already. > > >>>> I > > >>>> guess we could move the "acpi=force" argument passing to EFI_STUB if no > > >>>> DT is present at boot. > > >>> > > >>> Since the EFI stub populates the /chosen node in DT, I would prefer > > >>> for it to add a property there to indicate whether it created the DT > > >>> from scratch rather than adding ACPI specific stuff in there (even if > > >>> it is just a string to concatenate) > > >> > > >> This works for me. So we could pass "acpi=force" in EFI stub if it > > >> created the DT from scratch *and* ACPI tables are present (can it detect > > >> the latter? And maybe it could print something if none are available). > > >> If that works, the actual kernel can assume that ACPI needs to be > > >> explicitly enabled via acpi=force, irrespective of how much information > > >> it has in DT. > > > > > > Ditto for me. I think this is a fine solution. And, yes, the stub can > > > easily detect the presence of ACPI by looking in the UEFI config table. > > > > I get the point behind doing this, but could we not have it pass in a > > different parameter than =force? Perhaps something new? I'd like to > > separate out the case that it was enabled automatically vs explicitly > > forced on by a user wanting to use ACPI on a system with both tables. > > Ard had a point, so we should probably not pass acpi=force from EFI stub > (especially since a user may explicitly pass acpi=off irrespective of DT > presence). Some other property in the chosen node? It's not even an ABI > since that's a contract between EFI stub and the rest of the kernel, so > an in-kernel only interface.
Not strictly true once kexec is in place. Then it becomes a stub -> kernel -> kernel -> kernel -> ... interface, alnog with the rest of the properties the stub puts in the DTB. Having something like /chosen/linux,uefi-stub-generated-dtb sounds sane regardless. Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
