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read_persistent_clock uses a global variable, use a spinlock to ensure non-atomic updates to the variable don't overlap and cause time to move backwards. Signed-off-by: Colin Cross <ccross@android.com> Signed-off-by: R Sricharan <r.sricharan@ti.com> Cc: stable@vger.kernel.org Signed-off-by: Tony Lindgren <tony@atomide.com>
125 lines
3.6 KiB
C
125 lines
3.6 KiB
C
/*
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* OMAP 32ksynctimer/counter_32k-related code
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*
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* Copyright (C) 2009 Texas Instruments
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* Copyright (C) 2010 Nokia Corporation
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* Tony Lindgren <tony@atomide.com>
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* Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* NOTE: This timer is not the same timer as the old OMAP1 MPU timer.
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/clk.h>
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#include <linux/err.h>
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#include <linux/io.h>
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#include <linux/clocksource.h>
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#include <asm/mach/time.h>
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#include <asm/sched_clock.h>
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#include <plat/common.h>
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#include <plat/clock.h>
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/* OMAP2_32KSYNCNT_CR_OFF: offset of 32ksync counter register */
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#define OMAP2_32KSYNCNT_REV_OFF 0x0
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#define OMAP2_32KSYNCNT_REV_SCHEME (0x3 << 30)
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#define OMAP2_32KSYNCNT_CR_OFF_LOW 0x10
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#define OMAP2_32KSYNCNT_CR_OFF_HIGH 0x30
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/*
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* 32KHz clocksource ... always available, on pretty most chips except
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* OMAP 730 and 1510. Other timers could be used as clocksources, with
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* higher resolution in free-running counter modes (e.g. 12 MHz xtal),
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* but systems won't necessarily want to spend resources that way.
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*/
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static void __iomem *sync32k_cnt_reg;
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static u32 notrace omap_32k_read_sched_clock(void)
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{
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return sync32k_cnt_reg ? __raw_readl(sync32k_cnt_reg) : 0;
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}
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/**
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* omap_read_persistent_clock - Return time from a persistent clock.
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*
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* Reads the time from a source which isn't disabled during PM, the
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* 32k sync timer. Convert the cycles elapsed since last read into
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* nsecs and adds to a monotonically increasing timespec.
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*/
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static struct timespec persistent_ts;
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static cycles_t cycles;
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static unsigned int persistent_mult, persistent_shift;
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static DEFINE_SPINLOCK(read_persistent_clock_lock);
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static void omap_read_persistent_clock(struct timespec *ts)
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{
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unsigned long long nsecs;
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cycles_t last_cycles;
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unsigned long flags;
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spin_lock_irqsave(&read_persistent_clock_lock, flags);
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last_cycles = cycles;
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cycles = sync32k_cnt_reg ? __raw_readl(sync32k_cnt_reg) : 0;
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nsecs = clocksource_cyc2ns(cycles - last_cycles,
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persistent_mult, persistent_shift);
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timespec_add_ns(&persistent_ts, nsecs);
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*ts = persistent_ts;
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spin_unlock_irqrestore(&read_persistent_clock_lock, flags);
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}
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/**
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* omap_init_clocksource_32k - setup and register counter 32k as a
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* kernel clocksource
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* @pbase: base addr of counter_32k module
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* @size: size of counter_32k to map
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*
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* Returns 0 upon success or negative error code upon failure.
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*
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*/
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int __init omap_init_clocksource_32k(void __iomem *vbase)
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{
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int ret;
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/*
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* 32k sync Counter IP register offsets vary between the
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* highlander version and the legacy ones.
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* The 'SCHEME' bits(30-31) of the revision register is used
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* to identify the version.
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*/
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if (__raw_readl(vbase + OMAP2_32KSYNCNT_REV_OFF) &
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OMAP2_32KSYNCNT_REV_SCHEME)
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sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_HIGH;
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else
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sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_LOW;
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/*
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* 120000 rough estimate from the calculations in
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* __clocksource_updatefreq_scale.
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*/
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clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
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32768, NSEC_PER_SEC, 120000);
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ret = clocksource_mmio_init(sync32k_cnt_reg, "32k_counter", 32768,
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250, 32, clocksource_mmio_readl_up);
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if (ret) {
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pr_err("32k_counter: can't register clocksource\n");
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return ret;
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}
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setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
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register_persistent_clock(NULL, omap_read_persistent_clock);
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pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
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return 0;
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}
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