[PATCH 5/7] x86/rtc: mach_get_cmos_time - rm duplicated code
From: Mateusz Jończyk <hidden>
Date: 2021-09-12 12:43:35
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
There are functions in drivers/rtc/rtc-mc146818-lib.c that handle
reading from / writing to the CMOS RTC clock. mach_get_cmos_time() in
arch/x86/kernel/rtc.c did not use them and was mostly a duplicate of
mc146818_get_time(). Modify mach_get_cmos_time() to use
mc146818_get_time() and remove the duplicated code.
mach_get_cmos_time() used a different algorithm than
mc146818_get_time(), but these functions are equivalent. The major
differences are:
- mc146818_get_time() is better refined: it was updated in
commit 05a0302c3548 ("rtc: mc146818: Prevent reading garbage")
to take account of various edge conditions,
- when the UIP ("Update in progress") bit of the RTC is set,
mach_get_cmos_time() was busy waiting with cpu_relax() while
mc146818_get_time() is now using udelay(100) in every loop iteration,
- mach_get_cmos_time() assumed that the RTC year must be >= 2000, which
may not be true on some old boxes with a dead battery.
The RTC writing counterpart, mach_set_rtc_mmss() is already using
mc146818_get_time() from drivers/rtc. This was done in
commit 3195ef59cb42 ("x86: Do full rtc synchronization with ntp")
It appears that mach_get_cmos_time() was simply forgotten.
Signed-off-by: Mateusz Jończyk <redacted>
Cc: Thomas Gleixner <redacted>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
arch/x86/kernel/rtc.c | 55 +++++--------------------------------------
1 file changed, 6 insertions(+), 49 deletions(-)
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 586f718b8e95..bd170362edef 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c@@ -20,15 +20,12 @@ /* * This is a special lock that is owned by the CPU and holds the index * register we are working with. It is required for NMI access to the - * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details. + * CMOS/RTC registers. See arch/x86/include/asm/mc146818rtc.h for details. */ volatile unsigned long cmos_lock; EXPORT_SYMBOL(cmos_lock); #endif /* CONFIG_X86_32 */ -/* For two digit years assume time is always after that */ -#define CMOS_YEARS_OFFS 2000 - DEFINE_SPINLOCK(rtc_lock); EXPORT_SYMBOL(rtc_lock);
@@ -62,8 +59,7 @@ int mach_set_rtc_mmss(const struct timespec64 *now) void mach_get_cmos_time(struct timespec64 *now) { - unsigned int status, year, mon, day, hour, min, sec, century = 0; - unsigned long flags; + struct rtc_time tm; /* * If pm_trace abused the RTC as storage, set the timespec to 0,
@@ -74,51 +70,12 @@ void mach_get_cmos_time(struct timespec64 *now) return; } - spin_lock_irqsave(&rtc_lock, flags); - - /* - * If UIP is clear, then we have >= 244 microseconds before - * RTC registers will be updated. Spec sheet says that this - * is the reliable way to read RTC - registers. If UIP is set - * then the register access might be invalid. - */ - while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)) - cpu_relax(); - - sec = CMOS_READ(RTC_SECONDS); - min = CMOS_READ(RTC_MINUTES); - hour = CMOS_READ(RTC_HOURS); - day = CMOS_READ(RTC_DAY_OF_MONTH); - mon = CMOS_READ(RTC_MONTH); - year = CMOS_READ(RTC_YEAR); - -#ifdef CONFIG_ACPI - if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && - acpi_gbl_FADT.century) - century = CMOS_READ(acpi_gbl_FADT.century); -#endif - - status = CMOS_READ(RTC_CONTROL); - WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY)); - - spin_unlock_irqrestore(&rtc_lock, flags); - - if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) { - sec = bcd2bin(sec); - min = bcd2bin(min); - hour = bcd2bin(hour); - day = bcd2bin(day); - mon = bcd2bin(mon); - year = bcd2bin(year); + if (!mc146818_get_time(&tm)) { + now->tv_sec = now->tv_nsec = 0; + return; } - if (century) { - century = bcd2bin(century); - year += century * 100; - } else - year += CMOS_YEARS_OFFS; - - now->tv_sec = mktime64(year, mon, day, hour, min, sec); + now->tv_sec = rtc_tm_to_time64(&tm); now->tv_nsec = 0; }
--
2.25.1