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Date: Thu, 19 Dec 2013 15:51:53 +0800
From: "Lee, Chun-Yi" <joeyli.kernel@...il.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Alessandro Zummo <a.zummo@...ertech.it>,
"H. Peter Anvin" <hpa@...or.com>,
Matt Fleming <matt@...sole-pimps.org>,
Matthew Garrett <matthew.garrett@...ula.com>
Cc: Elliott@...com, samer.el-haj-mahmoud@...com,
Oliver Neukum <oneukum@...e.de>, werner@...e.com,
trenn@...e.de, JBeulich@...e.com, linux-kernel@...r.kernel.org,
rtc-linux@...glegroups.com, x86@...nel.org,
"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
linux-acpi@...r.kernel.org, "Lee, Chun-Yi" <jlee@...e.com>
Subject: [RFC PATCH 12/14] efi: adjust system time base on timezone from EFI time services
EFI time services provide the interface to store timezone to BIOS. The
timezone value from EFI indicates the offset of RTC time in minutes from
UTC.
The formula is: Localtime = UTC - TimeZone.
This patch add a efI_warp_clock() function to initial process for adjust
system time base on timezone value from EFI time services. It will also
set persistent_clock_is_local global variable to avoid user space
adjust timezone again.
This efi warp clock mechanism will triggered on x86_64 EFI machine when
timezone value is neither 0 nor 2047(UNSPECIFIED), kernel assume the
value of RTC is local time. On the other hand, system just follow
the old logic when timezone value from EFI is 0 or 2047, kernel assume
the value of RTC is UTC time.
About the 2047(EFI_UNSPECIFIED_TIMEZONE) value, it's the default value
of UEFI BIOS if there didn't have software set it through EFI interface.
We can _NOT_ follow EFI spec to interpret the RTC time as a local time
if timezone value is EFI_UNSPECIFIED_TIMEZONE, that's because Linux stored
UTC to BIOS on shipped UEFI machines.
Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
---
arch/x86/platform/efi/efi.c | 37 +++++++++++++++++++++++++++++++++++++
include/linux/efi.h | 2 ++
init/main.c | 5 +++++
kernel/time.c | 2 +-
4 files changed, 45 insertions(+), 1 deletions(-)
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 42d6052..848160e 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -306,6 +306,43 @@ static void efi_get_time(struct timespec *now)
now->tv_nsec = 0;
}
+static int efi_read_timezone(s16 *timezone)
+{
+ efi_status_t status;
+ efi_time_t eft;
+ efi_time_cap_t cap;
+
+ status = efi.get_time(&eft, &cap);
+
+ if (status != EFI_SUCCESS) {
+ /* should never happen */
+ pr_err("efitime: can't read timezone.\n");
+ return -EINVAL;
+ }
+
+ *timezone = (s16)le16_to_cpu(eft.timezone);
+ return 0;
+}
+
+void __init efi_warp_clock(void)
+{
+ s16 timezone;
+
+ if (!efi_read_timezone(&timezone)) {
+ /* TimeZone value, 2047 or 0 means UTC */
+ if (timezone != 0 && timezone != 2047) {
+ struct timespec adjust;
+
+ persistent_clock_is_local = 1;
+ adjust.tv_sec = timezone * 60;
+ adjust.tv_nsec = 0;
+ timekeeping_inject_offset(&adjust);
+ pr_info("RTC timezone is %d mins behind of UTC.\n", timezone);
+ pr_info("Adjusted system time to UTC.\n");
+ }
+ }
+}
+
/*
* Tell the kernel about the EFI memory map. This might include
* more than the max 128 entries that can fit in the e820 legacy
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 1c78ae7..a8d4f5c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -715,10 +715,12 @@ extern void efi_memmap_walk (efi_freemem_callback_t callback, void *arg);
extern void efi_gettimeofday (struct timespec *ts);
extern void efi_enter_virtual_mode (void); /* switch EFI to virtual mode, if possible */
#ifdef CONFIG_X86
+extern void efi_warp_clock(void);
extern void efi_late_init(void);
extern void efi_free_boot_services(void);
extern efi_status_t efi_query_variable_store(u32 attributes, unsigned long size);
#else
+static inline void efi_warp_clock(void) {}
static inline void efi_late_init(void) {}
static inline void efi_free_boot_services(void) {}
diff --git a/init/main.c b/init/main.c
index 61164ce..9effb1c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -570,6 +570,11 @@ asmlinkage void __init start_kernel(void)
hrtimers_init();
softirq_init();
timekeeping_init();
+#ifdef CONFIG_X86_64
+ /* adjust system time by timezone */
+ if (efi_enabled(EFI_RUNTIME_SERVICES))
+ efi_warp_clock();
+#endif
time_init();
sched_clock_postinit();
perf_event_init();
diff --git a/kernel/time.c b/kernel/time.c
index 7c7964c..ce18bac 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -176,7 +176,7 @@ int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz)
update_vsyscall_tz();
if (firsttime) {
firsttime = 0;
- if (!tv)
+ if (!tv && !persistent_clock_is_local)
warp_clock();
}
}
--
1.6.4.2
--
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