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.marinas@xxxxxxx> > > wrote: > >> On Mon, Jan 19, 2015 at 11:55:32AM +0000, Ard Biesheuvel wrote: > >>> On 19 January 2015 at 11:42, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > >>>> On Wed, Jan 14, 2015 at 03:04:52PM +0000, Hanjun Guo wrote: > >>>>> From: Al Stone <al.stone@xxxxxxxxxx> > >>>>> > >>>>> 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. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
