On Tue, Jan 20, 2015 at 09:29:14AM +0000, Hanjun Guo wrote: > On 2015年01月20日 02:01, Mark Rutland wrote: > > 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.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. > > > > 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. > > How about the patch (just RFC, maybe it is horrible :) ) below: > > When system supporting both DT and ACPI but firmware providing > no dtb, we can use this linux,uefi-stub-generated-dtb property > to let kernel know that we can try ACPI configuration data. > > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx> I'm ok with the idea but I'll let Mark comment on the DT aspects. -- 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
