Re: [PATCH 1/2] riscv-platform-spec: Real-time Clock to server extension


Abner Chang
 



Heinrich Schuchardt <xypron.glpk@...> 於 2021年6月28日 週一 下午4:32寫道:
On 6/28/21 8:39 AM, Abner Chang wrote:
>
>
> Jonathan Behrens <behrensj@... <mailto:behrensj@...>> 於 2021年6
> 月25日 週五 下午11:11寫道:
>
>     Any chance that we can ban EFI_UNSPECIFIED_TIMEZONE and/or require
>     that time is always UTC?
>
> That depends on how do you implement GetTime/SetTime functions for the
> platform.  You can always not returning EFI_UNSPECIFIED_TIMEZONE in the
> implementation and just return the offset to UTC for the local time.
>
> Abner

The way that UEFI reports local time zones is unsatisfactory:

There is an offset to UTC and a daylight savings flag but this does not
allow to derive on which day daylight saving switches (you could be on
the southern or on the northern hemisphere) nor the daylight savings
offset which historically has been one hour or two hours.

Furthermore many RTC chips do not store timezone related information.
EDK II stores it in UEFI variables. There is no handling of daylight
savings switches in EDK II.

With this background allowing anything else but UTC just creates ambiguity.
That's true.

On the server platform, RTC doesn't work alone. It incorporates with BMC to get the time information because only BMC is alive even when the system is powered off. The system only syncs up the time settings from BMC when every time the system boots. GetTime function is used by the firmware or the pre-OS EFI applications. SetTIme is used when the firmware sync up the time with BMC or the server deployment. RTC is the media to keep the time information, how to use RTC is implementation-specific.
Abner

>
>
>     Jonathan
>
>
>     On Fri, Jun 25, 2021 at 10:35 AM Abner Chang via lists.riscv.org
>     <http://lists.riscv.org> <renba.chang=gmail.com@...
>     <mailto:gmail.com@...>> wrote:
>
>         From: Abner Chang <abner.chang@... <mailto:abner.chang@...>>
>
>         RTC (Real-time Clock)
>             Real-time clock is the server basic system peripheral to
>         provide the real date/time information for server to manage the
>         system date, time and time zones settings for different regions
>         through the local POST time firmware utility, NTP or the remote
>         management such as Redfish.
>
>         Signed-off-by: Abner Chang <renba.chang@...
>         <mailto:renba.chang@...>>
>         Signed-off-by: Abner Chang <abner.chang@...
>         <mailto:abner.chang@...>>
>         ---
>           riscv-platform-spec.adoc | 17 ++++++++++++++---
>           1 file changed, 14 insertions(+), 3 deletions(-)
>
>         diff --git a/riscv-platform-spec.adoc b/riscv-platform-spec.adoc
>         index 87ea6d5..d611d69 100644
>         --- a/riscv-platform-spec.adoc
>         +++ b/riscv-platform-spec.adoc
>         @@ -442,9 +442,9 @@ The UEFI run time services listed below are
>         required to be implemented.
>           |SetVariable               | 8.2        | A dedicated storage
>         for firmware is
>           required so that there is no conflict in access by both
>         firmware and the OS.
>           |QueryVariableInfo         | 8.2        |
>         -|GetTime                   | 8.3        | RTC Access by the OS
>         -|SetTime                   | 8.3        | If it is not possible
>         to set the RTC,
>         -the SetTime() can return an error.
>         +|GetTime                   | 8.3        | RTC Access by the OS
>         and firmware
>         +|SetTime                   | 8.3        | RTC configured by the
>         OS and
>         +firmware
>           |GetWakeupTime             | 8.3        | Interface is
>         required to be
>           implemented but it can return EFI_UNSUPPORTED.
>           |SetWakeupTime             | 8.3        | Interface is
>         required to be
>         @@ -469,6 +469,17 @@
>         https://lists.riscv.org/g/tech-privileged/message/404[Sstc]
>         <https://lists.riscv.org/g/tech-privileged/message/404%5BSstc%5D> extension.
>           ** Platforms are required to delegate the supervisor timer
>         interrupt to 'S'
>           mode. If the 'H' extension is implemented then the platforms
>         are required to
>           delegate the virtual supervisor timer interrupt to 'VS' mode.
>         +
>         +* Real-time Clock (RTC)
>         +The Real-time clock must be provided to the server extension
>         platform to
>         +facilitate the time management (Date, time and the time zone)
>         and RTC wake up
>         +when the server is in the power down state for the server
>         manageability.
>         +The GetTime()and SetTime() UEFI runtime services must be
>         implemented by
>         +firmware to incorporate with RTC and flexibly support RTC use
>         cases.
>         +GetWakeupTime() and SetWakeupTime() UEFI runtime services are
>         required to be
>         +implemented but it can return EFI_UNSUPPORTED if the wake up
>         from RTC is not
>         +supported.

This paragraph is self-contradictory:

It requires RTC to facilitate "RTC wake up" but allows SetWakeupTime()
to report EFI_UNSUPPORTED.

Best regards

Heinrich

>         +
>           * PCI-E
>
>           ==== Secure Boot
>         --
>         2.19.0.windows.1
>

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