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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/arm/plat-omap/counter_32k.c
Initial import
Diffstat (limited to 'arch/arm/plat-omap/counter_32k.c')
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1 files changed, 117 insertions, 0 deletions
diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c
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+++ b/arch/arm/plat-omap/counter_32k.c
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+/*
+ * OMAP 32ksynctimer/counter_32k-related code
+ *
+ * Copyright (C) 2009 Texas Instruments
+ * Copyright (C) 2010 Nokia Corporation
+ * Tony Lindgren <tony@atomide.com>
+ * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * NOTE: This timer is not the same timer as the old OMAP1 MPU timer.
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
+
+#include <asm/mach/time.h>
+
+#include <plat/counter-32k.h>
+
+/* OMAP2_32KSYNCNT_CR_OFF: offset of 32ksync counter register */
+#define OMAP2_32KSYNCNT_REV_OFF 0x0
+#define OMAP2_32KSYNCNT_REV_SCHEME (0x3 << 30)
+#define OMAP2_32KSYNCNT_CR_OFF_LOW 0x10
+#define OMAP2_32KSYNCNT_CR_OFF_HIGH 0x30
+
+/*
+ * 32KHz clocksource ... always available, on pretty most chips except
+ * OMAP 730 and 1510. Other timers could be used as clocksources, with
+ * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
+ * but systems won't necessarily want to spend resources that way.
+ */
+static void __iomem *sync32k_cnt_reg;
+
+static u64 notrace omap_32k_read_sched_clock(void)
+{
+ return sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
+}
+
+/**
+ * omap_read_persistent_clock64 - Return time from a persistent clock.
+ *
+ * Reads the time from a source which isn't disabled during PM, the
+ * 32k sync timer. Convert the cycles elapsed since last read into
+ * nsecs and adds to a monotonically increasing timespec64.
+ */
+static struct timespec64 persistent_ts;
+static cycles_t cycles;
+static unsigned int persistent_mult, persistent_shift;
+
+static void omap_read_persistent_clock64(struct timespec64 *ts)
+{
+ unsigned long long nsecs;
+ cycles_t last_cycles;
+
+ last_cycles = cycles;
+ cycles = sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
+
+ nsecs = clocksource_cyc2ns(cycles - last_cycles,
+ persistent_mult, persistent_shift);
+
+ timespec64_add_ns(&persistent_ts, nsecs);
+
+ *ts = persistent_ts;
+}
+
+/**
+ * omap_init_clocksource_32k - setup and register counter 32k as a
+ * kernel clocksource
+ * @pbase: base addr of counter_32k module
+ * @size: size of counter_32k to map
+ *
+ * Returns 0 upon success or negative error code upon failure.
+ *
+ */
+int __init omap_init_clocksource_32k(void __iomem *vbase)
+{
+ int ret;
+
+ /*
+ * 32k sync Counter IP register offsets vary between the
+ * highlander version and the legacy ones.
+ * The 'SCHEME' bits(30-31) of the revision register is used
+ * to identify the version.
+ */
+ if (readl_relaxed(vbase + OMAP2_32KSYNCNT_REV_OFF) &
+ OMAP2_32KSYNCNT_REV_SCHEME)
+ sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_HIGH;
+ else
+ sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_LOW;
+
+ /*
+ * 120000 rough estimate from the calculations in
+ * __clocksource_update_freq_scale.
+ */
+ clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
+ 32768, NSEC_PER_SEC, 120000);
+
+ ret = clocksource_mmio_init(sync32k_cnt_reg, "32k_counter", 32768,
+ 250, 32, clocksource_mmio_readl_up);
+ if (ret) {
+ pr_err("32k_counter: can't register clocksource\n");
+ return ret;
+ }
+
+ sched_clock_register(omap_32k_read_sched_clock, 32, 32768);
+ register_persistent_clock(NULL, omap_read_persistent_clock64);
+ pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
+
+ return 0;
+}