[U-Boot] [PATCH v2 1/2] x86: Add efi runtime reset

[Simon Glass]

Hi Alex,

On Mon, 28 Jan 2019 at 12:34, Alexander Graf <agraf at suse.de> wrote:
>
>
>
> On 28.01.19 20:31, Simon Glass wrote:
> > Hi Alex,
> >
> > On Mon, 28 Jan 2019 at 12:27, Alexander Graf <agraf at suse.de> wrote:
> >>
> >>
> >>
> >> On 28.01.19 20:24, Simon Glass wrote:
> >>> Hi Alex,
> >>>
> >>> On Mon, 28 Jan 2019 at 12:15, Alexander Graf <agraf at suse.de> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On 28.01.19 20:13, Simon Glass wrote:
> >>>>> Hi,
> >>>>>
> >>>>> On Mon, 28 Jan 2019 at 08:42, Alexander Graf <agraf at suse.de> wrote:
> >>>>>>
> >>>>>> Our selftest will soon test the actual runtime reset function rather than
> >>>>>> the boot time one. For this, we need to ensure that the runtime version
> >>>>>> actually succeeds on x86 to keep our travis tests work.
> >>>>>>
> >>>>>> So this patch implements an x86 runtime reset function. It is missing
> >>>>>> shutdown functionality today, but OSs usually implement that via ACPI
> >>>>>> and this function does more than the stub from before, so it's at least
> >>>>>> an improvement.
> >>>>>>
> >>>>>> Signed-off-by: Alexander Graf <agraf at suse.de>
> >>>>>> ---
> >>>>>>  drivers/sysreset/sysreset_x86.c | 23 +++++++++++++++++++++++
> >>>>>>  1 file changed, 23 insertions(+)
> >>>>>>
> >>>>>> diff --git a/drivers/sysreset/sysreset_x86.c b/drivers/sysreset/sysreset_x86.c
> >>>>>> index 20b958cfd4..efed45ccb7 100644
> >>>>>> --- a/drivers/sysreset/sysreset_x86.c
> >>>>>> +++ b/drivers/sysreset/sysreset_x86.c
> >>>>>> @@ -10,6 +10,29 @@
> >>>>>>  #include <sysreset.h>
> >>>>>>  #include <asm/io.h>
> >>>>>>  #include <asm/processor.h>
> >>>>>> +#include <efi_loader.h>
> >>>>>> +
> >>>>>> +#ifdef CONFIG_EFI_LOADER
> >>>>>> +void __efi_runtime EFIAPI efi_reset_system(
> >>>>>> +                       enum efi_reset_type reset_type,
> >>>>>> +                       efi_status_t reset_status,
> >>>>>> +                       unsigned long data_size, void *reset_data)
> >>>>>> +{
> >>>>>> +       u32 value = 0;
> >>>>>> +
> >>>>>> +       if (reset_type == EFI_RESET_COLD)
> >>>>>> +               value = SYS_RST | RST_CPU | FULL_RST;
> >>>>>> +       else if (reset_type == EFI_RESET_WARM)
> >>>>>> +               value = SYS_RST | RST_CPU;
> >>>>>
> >>>>> The EFI should use the sysreset driver and sysreset_walk() or similar,
> >>>>> rather than having a function called directly.
> >>>>
> >>>> It can't. At this point all of DM is long gone. We're in runtime space here.
> >>>
> >>> This has come up before. We'll end up with a lot of duplication if we
> >>> cannot solve this. I think the run-time code will need to be built and
> >>> linked separately so that all necessary code is pulled in.
> >>
> >> It's mostly a question of size. We can even transform all of U-Boot into
> >> huge runtime services if we keep the relocation tables around and apply
> >> relocations manually for everything.
> >>
> >> The problem is that if we do that, we'll become even bigger than we are
> >> now, no?
> >
> > I did a change to build U-Boot as a library, perhaps it could build on
> > that. The 'run-time U-Boot' won't be any bigger than the code that is
> > actually used. Also I don't think memory usage is a concern in systems
> > that use UEFI :-)
>
> It is, we're already exploding some constraints today. Furthermore, by
> moving all of U-Boot into RTS you obviously waste a few MB of RAM while
> Linux is up. And it's much harder to review that the code is only doing
> what you want it to do.

My suggest is not to move all of U-Boot into RTS. It is to build an
RTS version of U-Boot with just those things that are needed, a bit
like TPL or SPL.

I did not invent the run-time aspect of EFI, but I feel we are trying
to support it with a hack.

>
> > The problem with the current approach is that everything becomes
> > parallel to DM, duplicating existing code, and that is complicated
> > too.
>
> No, not everything. Only reset/shutdown. Well, and maybe variable
> services. Which may use SPI. Meh.

That should be a fairly small build, then.

Regards,
Simon