95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
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/*
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* Machine dependent access functions for RTC registers.
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*/
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#ifndef _ASM_MC146818RTC_H
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#define _ASM_MC146818RTC_H
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#include <asm/io.h>
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#include <asm/system.h>
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#include <linux/mc146818rtc.h>
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#ifndef RTC_PORT
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#define RTC_PORT(x) (0x70 + (x))
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#define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
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#endif
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#ifdef __HAVE_ARCH_CMPXCHG
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/*
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* This lock provides nmi access to the CMOS/RTC registers. It has some
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* special properties. It is owned by a CPU and stores the index register
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* currently being accessed (if owned). The idea here is that it works
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* like a normal lock (normally). However, in an NMI, the NMI code will
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* first check to see if its CPU owns the lock, meaning that the NMI
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* interrupted during the read/write of the device. If it does, it goes ahead
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* and performs the access and then restores the index register. If it does
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* not, it locks normally.
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*
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* Note that since we are working with NMIs, we need this lock even in
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* a non-SMP machine just to mark that the lock is owned.
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*
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* This only works with compare-and-swap. There is no other way to
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* atomically claim the lock and set the owner.
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*/
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#include <linux/smp.h>
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extern volatile unsigned long cmos_lock;
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/*
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* All of these below must be called with interrupts off, preempt
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* disabled, etc.
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*/
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static inline void lock_cmos(unsigned char reg)
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{
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unsigned long new;
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new = ((smp_processor_id()+1) << 8) | reg;
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for (;;) {
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if (cmos_lock)
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continue;
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if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
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return;
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}
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}
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static inline void unlock_cmos(void)
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{
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cmos_lock = 0;
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}
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static inline int do_i_have_lock_cmos(void)
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{
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return (cmos_lock >> 8) == (smp_processor_id()+1);
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}
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static inline unsigned char current_lock_cmos_reg(void)
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{
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return cmos_lock & 0xff;
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}
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#define lock_cmos_prefix(reg) \
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do { \
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unsigned long cmos_flags; \
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local_irq_save(cmos_flags); \
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lock_cmos(reg)
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#define lock_cmos_suffix(reg) \
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unlock_cmos(); \
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local_irq_restore(cmos_flags); \
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} while (0)
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#else
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#define lock_cmos_prefix(reg) do {} while (0)
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#define lock_cmos_suffix(reg) do {} while (0)
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#define lock_cmos(reg)
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#define unlock_cmos()
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#define do_i_have_lock_cmos() 0
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#define current_lock_cmos_reg() 0
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#endif
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/*
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* The yet supported machines all access the RTC index register via
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* an ISA port access but the way to access the date register differs ...
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*/
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#define CMOS_READ(addr) rtc_cmos_read(addr)
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#define CMOS_WRITE(val, addr) rtc_cmos_write(val, addr)
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unsigned char rtc_cmos_read(unsigned char addr);
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void rtc_cmos_write(unsigned char val, unsigned char addr);
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#define RTC_IRQ 8
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#endif /* _ASM_MC146818RTC_H */
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