From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Lee, Chun-Yi" Subject: [RFC PATCH 12/14] efi: adjust system time base on timezone from EFI time services Date: Thu, 19 Dec 2013 15:51:53 +0800 Message-ID: <1387439515-8926-13-git-send-email-jlee@suse.com> References: <1387439515-8926-1-git-send-email-jlee@suse.com> Return-path: In-Reply-To: <1387439515-8926-1-git-send-email-jlee@suse.com> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" , Alessandro Zummo , "H. Peter Anvin" , Matt Fleming , Matthew Garrett Cc: Elliott@hp.com, samer.el-haj-mahmoud@hp.com, Oliver Neukum , werner@suse.com, trenn@suse.de, JBeulich@suse.com, linux-kernel@vger.kernel.org, rtc-linux@googlegroups.com, x86@kernel.org, "linux-efi@vger.kernel.org" , linux-acpi@vger.kernel.org, "Lee, Chun-Yi" List-Id: linux-efi@vger.kernel.org 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 --- 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