[PATCH v2] Silicon/NXP/Pcf8563RealTimeClockLib: add Voltage-low handling

[masahisa.kojima@linaro.org]

From: Masahisa Kojima <masahisa.kojima@linaro.org>

BcdToDecimal8() in LibGetTime() asserts with the
following condition.
 1) RTC device has not been initialized yet, RTC device
    returns indeterminate value with VL bit(1)
 2) DEBUG build

UEFI boot fails with assertion when it satisfies above conditions.

Aside form boot failure, UEFI shell commands "date/time" expect
that getting time from RTC should success when user sets the time.
ShellCommandRunTime() performs GetTime()->update time->SetTime(),
if the first GetTime() fails, user can not set time.
With that, simply returning EFI_DEVICE_ERROR in LibGetTime()
is not applicable to VL bit handling.

To avoid this situation, even if it only occurs in DEBUG build,
RTC driver should check the VL bit in the VL_seconds register.
This VL bit is voltage-low detector, it means integrity of the
clock information is not guaranteed if it sets to 1. In this
case, driver return dummy date/time(01/01/2000 00:00:00) to
proceed succeeding process.

linux driver also checks this bit when driver gets the time
from RTC. If VL bit is 1, linux driver discard the retreived
time data.

Note that if VL bit is 1, GetTime() returns always
01/01/2000 00:00:00 until user sets date/time.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Signed-off-by: Yoshitoyo Osaki <osaki.yoshitoyo@socionext.com>
---
 .../Pcf8563RealTimeClockLib.c                      | 31 +++++++++++++++-------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/Silicon/NXP/Library/Pcf8563RealTimeClockLib/Pcf8563RealTimeClockLib.c b/Silicon/NXP/Library/Pcf8563RealTimeClockLib/Pcf8563RealTimeClockLib.c
index fb58e1feb4..9f49ae91de 100644
--- a/Silicon/NXP/Library/Pcf8563RealTimeClockLib/Pcf8563RealTimeClockLib.c
+++ b/Silicon/NXP/Library/Pcf8563RealTimeClockLib/Pcf8563RealTimeClockLib.c
@@ -19,11 +19,13 @@
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/UefiLib.h>
 #include <Library/UefiRuntimeLib.h>
+#include <Library/BaseMemoryLib.h>
 #include <Protocol/I2cMaster.h>
 
 #define SLAVE_ADDRESS             (FixedPcdGet8 (PcdI2cSlaveAddress))
 #define PCF8563_DATA_REG_OFFSET   0x2
 
+#define PCF8563_CLOCK_INVALID     0x80
 #define PCF8563_SECONDS_MASK      0x7f
 #define PCF8563_MINUTES_MASK      0x7f
 #define PCF8563_HOURS_MASK        0x3f
@@ -95,6 +97,7 @@ LibGetTime (
   RTC_DATETIME                DateTime;
   EFI_STATUS                  Status;
   UINT8                       Reg;
+  EFI_TIME                    InitTime;
 
   if (Time == NULL) {
     return EFI_INVALID_PARAMETER;
@@ -122,15 +125,25 @@ LibGetTime (
     return EFI_DEVICE_ERROR;
   }
 
-  Time->Second  = BcdToDecimal8 (DateTime.VL_seconds & PCF8563_SECONDS_MASK);
-  Time->Minute  = BcdToDecimal8 (DateTime.Minutes & PCF8563_MINUTES_MASK);
-  Time->Hour    = BcdToDecimal8 (DateTime.Hours & PCF8563_HOURS_MASK);
-  Time->Day     = BcdToDecimal8 (DateTime.Days & PCF8563_DAYS_MASK);
-  Time->Month   = BcdToDecimal8 (DateTime.Century_months & PCF8563_MONTHS_MASK);
-  Time->Year    = BcdToDecimal8 (DateTime.Years) + EPOCH_BASE;
-
-  if (DateTime.Century_months & PCF8563_CENTURY_MASK) {
-    Time->Year += 100;
+  if ((DateTime.VL_seconds & PCF8563_CLOCK_INVALID) != 0) {
+      InitTime.Second  = 0;
+      InitTime.Minute  = 0;
+      InitTime.Hour    = 0;
+      InitTime.Day     = 1;
+      InitTime.Month   = 1;
+      InitTime.Year    = EPOCH_BASE;
+      (VOID)CopyMem (Time, &InitTime, sizeof(EFI_TIME));
+  } else {
+      Time->Second  = BcdToDecimal8 (DateTime.VL_seconds & PCF8563_SECONDS_MASK);
+      Time->Minute  = BcdToDecimal8 (DateTime.Minutes & PCF8563_MINUTES_MASK);
+      Time->Hour    = BcdToDecimal8 (DateTime.Hours & PCF8563_HOURS_MASK);
+      Time->Day     = BcdToDecimal8 (DateTime.Days & PCF8563_DAYS_MASK);
+      Time->Month   = BcdToDecimal8 (DateTime.Century_months & PCF8563_MONTHS_MASK);
+      Time->Year    = BcdToDecimal8 (DateTime.Years) + EPOCH_BASE;
+
+      if (DateTime.Century_months & PCF8563_CENTURY_MASK) {
+          Time->Year += 100;
+      }
   }
 
   if (Capabilities != NULL) {
-- 
2.14.2