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

[Simon Glass]

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.

Regards,
Simon