[U-Boot] [PATCH v3 1/2] x86: Add efi runtime reset

[Alexander Graf]

> Am 31.01.2019 um 02:24 schrieb Simon Glass <sjg at chromium.org>:
> 
> Hi,
> 
>> On Wed, 30 Jan 2019 at 12:03, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>> 
>>> On 1/30/19 11:46 AM, Alexander Graf 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.
>>> 
>>> Eventually we will want to have full DM functionality in runtime services.
>>> But this fixes a travis failure and doesn't clutter the code too heavily, so
>>> we should pull it in without the amazing new RTS DM framework.
>>> 
>>> Signed-off-by: Alexander Graf <agraf at suse.de>
>>> 
>>> ---
>>> 
>>> v2 -> v3:
>>> 
>>>  - support EFI_RESET_PLATFORM_SPECIFIC
>>>  - reuse existing x86_sysreset_request() function
>> 
>> The v2->v3 update does not answer the question if the reset is correctly
>> implemented. We would not want to call a function we do not trust.
>> 
>> @Simon, Bin:
>> x86_sysreset_request() loosely resembles BOOT_CF9_SAFE in
>> native_machine_emergency_restart() in Linux arch/x86/kernel/reboot.c
>> which is tried before using the keyboard controller as last resort.
>> 
>> u8 reboot_code = reboot_mode == REBOOT_WARM ?  0x06 : 0x0E;
>> u8 cf9 = inb(0xcf9) & ~reboot_code;
>> outb(cf9|2, 0xcf9); /* Request hard reset */
>> udelay(50);
>> /* Actually do the reset */
>> outb(cf9|reboot_code, 0xcf9);
>> udelay(50);
>> 
>> So the Kernel first switches bit 2 off and bit 1 on, waits, and then
>> switches bit 2 on, cf.
>> http://smackerelofopinion.blogspot.com/2011/02/resetting-pc-using-reset-control.html
>> 
>> Shouldn't we do it the same way as the Kernel does it?
> 
> I suspect so, but Bin is the expert.
> 
> As to this patch, it perpetuates the current EFI run-time approach in
> U-Boot so I'm not sure this is the right path.

It is the right short- to mid-term plan. I rather have a shed I can live in today than a palace in 5 years :). Well, not true, I probably want both :).


Alex