Hi Daniel
-----Original Message----- From: arm.ebbr-discuss-bounces@arm.com <arm.ebbr-discuss- bounces@arm.com> On Behalf Of Daniel Thompson Sent: Tuesday, October 16, 2018 9:43 PM To: Grant Likely Grant.Likely@arm.com Cc: boot-architecture@lists.linaro.org; nd nd@arm.com; arm.ebbr-discuss arm.ebbr-discuss@arm.com Subject: Re: [Arm.ebbr-discuss] [PATCH v2] Refactor ResetSystem() requirements
On Thu, Oct 11, 2018 at 03:05:33PM +0000, Grant Likely wrote:
ResetSystem() was over-specified in the document. UEFI already documents the behaviour of ResetSystem() sufficiently. Add notes on expected behaviour when platform specific or standard interface methods are available.
Resolves: #29 Signed-off-by: Grant Likely grant.likely@arm.com
source/chapter2-uefi.rst | 27 ++++++++++----------------- 1 file changed, 10 insertions(+), 17 deletions(-)
diff --git a/source/chapter2-uefi.rst b/source/chapter2-uefi.rst index 0cbddff..8a3ff1a 100644 --- a/source/chapter2-uefi.rst +++ b/source/chapter2-uefi.rst @@ -175,23 +175,16 @@ and the OS must use a device driver to control the
RTC.
UEFI Reset and Shutdown
-The UEFI Runtime service ResetSystem() must implement the following commands, -for purposes of power management and system control.
-- EfiResetCold() -- EfiResetShutdown()
- EfiResetShutdown must not reboot the system.
-If firmware updates are supported through the Runtime Service of -UpdateCapsule(), then ResetSystem() might need to support the following -command:
-- EfiWarmReset()
-.. note:: On platforms implementing the Power State Coordination Interface
- specification [PSCI]_, it is still required that EBBR compliant
- Operating Systems calls to reset the system will go via Runtime Services
- and not directly to PSCI.
+ResetSystem() is required to be implemented in boot services, but it +is optional for runtime services. +During runtime services, the operating system should first attempt to +use ResetSystem() to reset the system.
This doesn't fit together quite as it should alongside the RuntimeServicesSupported variable. Read naively it appears to recommend that an OS call ResetSystem() even in cases where it knows that it doesn't work.
IMO, this variable is applicable for all services, not for just reset, right ? I am not sure, if this is bit mask in this variable to specify each runtime service availability,
fyi, I am not able to find such variable in Table 10. Global Variables (spec 2.7) Please help, where this is defined
It's a bit tricky to word since there are three cases rather than two (implemented, not-implemented and os-didn't-check)
Maybe: : ... unless the operating system has already discovered : from the "RuntimeServicesSupported" variable that ResetSystem() : is not implemented.
+If ResetSystem() returns EFI_UNSUPPORTED, then the OS may fall back +to an architecture or platform specific mechanism.
+On AArch64 platforms implementing [PSCI]_, if ResetSystem() is not +implemented then the Operating System should fall back to making a +PSCI call to reset or shutdown the system.
Runtime Variable Access
-- 2.13.0
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