EFI_STUB fails to boot non-EFI on arm64

[Leif Lindholm]

On Wed, May 28, 2014 at 04:59:31PM +0100, Will Deacon wrote:
> > > Can we add another of detecting whether it's an EFI application and
> > > avoid calling efi_init()? I can see x86 sets some efi_loader_signature
> > > string in exit_boot() and checks against it later when calling
> > > efi_init().
> > 
> > Well, I agree that we shouldn't be spewing error messages for expected
> > operation, but efi_init() is the function we call to determine
> > whether we _are_ booting via UEFI - and it sets flags accordingly for
> > the efi_enabled() macro.
> > 
> > My view is that this should be fixed in fdt_find_uefi_params(). A
> > single info message that we can't find evidence of UEFI should be
> > printed in the non-error case.
> > 
> > Like below?
> 
> Why not move the efi_get_fdt_params call out of efi_init and into
> setup_arch via a wrapper? Then efi_get_fdt_params and efi_init can have
> useful return values, which allow us to distinguish between "My DT doesn't
> have the necessary UEFI properties" and "UEFI failed to initialise" without
> having to make some printks pr_info and others pr_err within efi_init
> itself..

Well, but (for the output part) my patch already did that?
If the "Getting parameters from FDT:\n" was too verbose, we could
just drop it, and have the same effect on output.

Thing is - there is not really any error case available anywhere
during the execution of efi_init() and its branches other than:
- Information required for UEFI boot cannot be found.
- Information exists, but is invalid.
- Failed to early_memremap some UEFI regions into the kernel.
which all amounts to "UEFI not available or something went wrong",
rather than "UEFI failed to initialise".
If efi_init returns successfully, EFI_BOOT is set, and testable using
the efi_enabled() macro.

The proper "UEFI failed to initialise" bit does not come until the
early_initcall arm64_enter_virtual_mode(), and is indicated not by
a return value, but by setting the flag indicating that
EFI_RUNTIME_SERVICES are available, which is checked later in core
code using the efi_enabled() macro.

So moving the call to efi_get_fdt_params() would have little effect
other than adding a third call site for UEFI bits in setup_arch().

/
	Leif