[PATCH 2/2] efi/arm64: use UEFI for system reset

On 29 August 2014 18:04, Catalin Marinas [off-list ref] wrote:

On Fri, Aug 29, 2014 at 04:05:57PM +0100, Ard Biesheuvel wrote:

quoted

If UEFI Runtime Services are available, they are preferred over direct
PSCI calls or other methods to reset the system.

For the reset case, we need to hook into machine_restart(), as the
arm_pm_restart function pointer may be overwritten by modules.

Signed-off-by: Ard Biesheuvel <redacted>
---
 arch/arm64/kernel/process.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 1309d64aa926..335a93da5eeb 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c

@@ -177,6 +177,13 @@ void machine_restart(char *cmd)
      local_irq_disable();
      smp_send_stop();

+     /*
+      * arm_pm_restart is exported to modules, so the only way to supersede
+      * it with efi_reboot() is to call it here.
+      */

Why do you make this the preferred method? Is there a risk that UEFI is
broken and we want to override it with a SoC-specific driver (I wouldn't
like it but it's still an option).

For poweroff (the other patch), it may not make a huge difference, but
the SBBR does state it explicitly.

For reboot, we *have* to use EFI reboot in order to support capsules:
when using capsules (for instance, for updating the firmware), you
need to use EFI reboot as you need to pass the return code of
UpdateCapsule() (a runtime service) to ResetSystem()

There are also some patches here that try to get rid of arm_pm_restart:

https://lkml.org/lkml/2014/8/19/665

Once there are no drivers for arm64 setting arm_pm_restart explicitly
I'll remove it.

OK, good to know. I will revisit this once that stuff is in.

-- 
Ard.

quoted

+     if (IS_ENABLED(CONFIG_EFI) && efi_enabled(EFI_RUNTIME_SERVICES))

efi_enabled always returns false if !IS_ENABLED(CONFIG_EFI).

quoted

+             efi_reboot(REBOOT_WARM, NULL);
+
      /* Now call the architecture specific reboot code. */
      if (arm_pm_restart)
              arm_pm_restart(reboot_mode, cmd);
--
1.8.3.2

--
Catalin