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

[Alexander Graf]

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.

> 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.


Alex