Re: [PATCH v2 3/3] ArmPlatformPkg/PL031RealTimeClockLib: ignore DST setting when timezone is set

[Leif Lindholm <leif.lindholm@linaro.org>]

On Mon, Nov 06, 2017 at 06:20:38PM +0000, Ard Biesheuvel wrote:
> According to the UEFI spec, the timezone setting which the platform needs
> to record in addition to the actual date and time already reflects the
> current DST setting. In other words, moving the clock from standard time
> to daylight saving time also involves adding or subtracting 60 minutes
> from the timezone setting, as well as flicking the EFI_TIME_IN_DAYLIGHT
> bit in the DST setting.
> 
> This means we need to disregard the DST setting if the timezone is
> specified, and only add or subtract the additional hour if we are on
> local time.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Assuming I understand the above correctly, and page 259/260 in 2.7a:
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> ---
>  ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c b/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
> index f1eb0deb3249..459dcc0a0519 100644
> --- a/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
> +++ b/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
> @@ -164,12 +164,10 @@ LibGetTime (
>    }
>  
>    // Adjust for the correct time zone
> +  // The timezone setting also reflects the DST setting of the clock
>    if (Time->TimeZone != EFI_UNSPECIFIED_TIMEZONE) {
>      EpochSeconds += Time->TimeZone * SEC_PER_MIN;
> -  }
> -
> -  // Adjust for the correct period
> -  if ((Time->Daylight & EFI_TIME_IN_DAYLIGHT) == EFI_TIME_IN_DAYLIGHT) {
> +  } else if ((Time->Daylight & EFI_TIME_IN_DAYLIGHT) == EFI_TIME_IN_DAYLIGHT) {
>      // Convert to adjusted time, i.e. spring forwards one hour
>      EpochSeconds += SEC_PER_HOUR;
>    }
> @@ -229,12 +227,10 @@ LibSetTime (
>    EpochSeconds = EfiTimeToEpoch (Time);
>  
>    // Adjust for the correct time zone, i.e. convert to UTC time zone
> +  // The timezone setting also reflects the DST setting of the clock
>    if (Time->TimeZone != EFI_UNSPECIFIED_TIMEZONE) {
>      EpochSeconds -= Time->TimeZone * SEC_PER_MIN;
> -  }
> -
> -  // Adjust for the correct period
> -  if ((Time->Daylight & EFI_TIME_IN_DAYLIGHT) == EFI_TIME_IN_DAYLIGHT) {
> +  } else if ((Time->Daylight & EFI_TIME_IN_DAYLIGHT) == EFI_TIME_IN_DAYLIGHT) {
>      // Convert to un-adjusted time, i.e. fall back one hour
>      EpochSeconds -= SEC_PER_HOUR;
>    }
> -- 
> 2.11.0
>