x86: Do full rtc synchronization with ntp

Every 11 minutes ntp attempts to update the x86 rtc with the current
system time.  Currently, the x86 code only updates the rtc if the system
time is within +/-15 minutes of the current value of the rtc. This
was done originally to avoid setting the RTC if the RTC was in localtime
mode (common with Windows dualbooting).  Other architectures do a full
synchronization and now that we have better infrastructure to detect
when the RTC is in localtime, there is no reason that x86 should be
software limited to a 30 minute window.

This patch changes the behavior of the kernel to do a full synchronization
(year, month, day, hour, minute, and second) of the rtc when ntp requests
a synchronization between the system time and the rtc.

I've used the RTC library functions in this patchset as they do all the
required bounds checking.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: x86@kernel.org
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
[jstultz: Tweak commit message, fold in build fix found by fengguang
Also add select RTC_LIB to X86, per new dependency, as found by prarit]
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 16 insertions, 8 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 5f2ecaf3f9d8..28d9efacc9b6 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -48,6 +48,7 @@
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/x86_init.h>
+#include <asm/rtc.h>
 
 #define EFI_DEBUG       1
 
@@ -258,10 +259,10 @@ static efi_status_t __init phys_efi_get_time(efi_time_t *tm,
 
 int efi_set_rtc_mmss(unsigned long nowtime)
 {
-        int real_seconds, real_minutes;
         efi_status_t    status;
         efi_time_t      eft;
         efi_time_cap_t  cap;
+        struct rtc_time tm;
 
         status = efi.get_time(&eft, &cap);
         if (status != EFI_SUCCESS) {
@@ -269,13 +270,20 @@ int efi_set_rtc_mmss(unsigned long nowtime)
                 return -1;
         }
 
-        real_seconds = nowtime % 60;
-        real_minutes = nowtime / 60;
-        if (((abs(real_minutes - eft.minute) + 15)/30) & 1)
-                real_minutes += 30;
-        real_minutes %= 60;
-        eft.minute = real_minutes;
-        eft.second = real_seconds;
+        rtc_time_to_tm(nowtime, &tm);
+        if (!rtc_valid_tm(&tm)) {
+                eft.year = tm.tm_year + 1900;
+                eft.month = tm.tm_mon + 1;
+                eft.day = tm.tm_mday;
+                eft.minute = tm.tm_min;
+                eft.second = tm.tm_sec;
+                eft.nanosecond = 0;
+        } else {
+                printk(KERN_ERR
+                       "%s: Invalid EFI RTC value: write of %lx to EFI RTC failed\n",
+                       __FUNCTION__, nowtime);
+                return -1;
+        }
 
         status = efi.set_time(&eft);
         if (status != EFI_SUCCESS) {