/*
* drivers/clocksource/arm_global_timer.c
*
* Copyright (C) 2013 STMicroelectronics (R&D) Limited.
* Author: Stuart Menefy <stuart.menefy@st.com>
* Author: Srinivas Kandagatla <srinivas.kandagatla@st.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.
*/
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
#include <linux/sched_clock.h>
#include <asm/cputype.h>
#define GT_COUNTER0 0x00
#define GT_COUNTER1 0x04
#define GT_CONTROL 0x08
#define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */
#define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */
#define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */
#define GT_CONTROL_AUTO_INC BIT(3) /* banked */
#define GT_INT_STATUS 0x0c
#define GT_INT_STATUS_EVENT_FLAG BIT(0)
#define GT_COMP0 0x10
#define GT_COMP1 0x14
#define GT_AUTO_INC 0x18
/*
* We are expecting to be clocked by the ARM peripheral clock.
*
* Note: it is assumed we are using a prescaler value of zero, so this is
* the units for all operations.
*/
static void __iomem *gt_base;
static unsigned long gt_clk_rate;
static int gt_ppi;
static struct clock_event_device __percpu *gt_evt;
/*
* To get the value from the Global Timer Counter register proceed as follows:
* 1. Read the upper 32-bit timer counter register
* 2. Read the lower 32-bit timer counter register
* 3. Read the upper 32-bit timer counter register again. If the value is
* different to the 32-bit upper value read previously, go back to step 2.
* Otherwise the 64-bit timer counter value is correct.
*/
static u64 gt_counter_read(void)
{
u64 counter;
u32 lower;
u32 upper, old_upper;
upper = readl_relaxed(gt_base + GT_COUNTER1);
do {
old_upper = upper;
lower = readl_relaxed(gt_base + GT_COUNTER0);
upper = readl_relaxed(gt_base + GT_COUNTER1);
} while (upper != old_upper);
counter = upper;
counter <<= 32;
counter |= lower;
return counter;
}
/**
* To ensure that updates to comparator value register do not set the
* Interrupt Status Register proceed as follows:
* 1. Clear the Comp Enable bit in the Timer Control Register.
* 2. Write the lower 32-bit Comparator Value Register.
* 3. Write the upper 32-bit Comparator Value Register.
* 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
*/
static void gt_compare_set(unsigned long delta, int periodic)
{
u64 counter = gt_counter_read();
unsigned long ctrl;
counter += delta;
ctrl = GT_CONTROL_TIMER_ENABLE;
writel(ctrl, gt_base + GT_CONTROL);
writel(lower_32_bits(counter), gt_base + GT_COMP0);
writel(upper_32_bits(counter), gt_base + GT_COMP1);
if (periodic) {
writel(delta, gt_base + GT_AUTO_INC);
ctrl |= GT_CONTROL_AUTO_INC;
}
ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
writel(ctrl, gt_base + GT_CONTROL);
}
static void gt_clockevent_set_mode(enum clock_event_mode mode,
struct clock_event_device *clk)
{
unsigned long ctrl;
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
break;
case CLOCK_EVT_MODE_ONESHOT:
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
ctrl = readl(gt_base + GT_CONTROL);
ctrl &= ~(GT_CONTROL_COMP_ENABLE |
GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC);
writel(ctrl, gt_base + GT_CONTROL);
break;
default:
break;
}
}
static int gt_clockevent_set_next_event(unsigned long evt,
struct clock_event_device *unused)
{
gt_compare_set(evt, 0);
return 0;
}
static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = dev_id;
if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
GT_INT_STATUS_EVENT_FLAG))
return IRQ_NONE;
/**
* ERRATA 740657( Global Timer can send 2 interrupts for
* the same event in single-shot mode)
* Workaround:
* Either disable single-shot mode.
* Or
* Modify the Interrupt Handler to avoid the
* offending sequence. This is achieved by clearing
* the Global Timer flag _after_ having incremented
* the Comparator register value to a higher value.
*/
if (evt->mode == CLOCK_EVT_MODE_ONESHOT)
gt_compare_set(ULONG_MAX, 0);
writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
evt->event_handler(evt);
return IRQ_HANDLED;
}
static int gt_clockevents_init(struct clock_event_device *clk)
{
int cpu = smp_processor_id();
clk->name = "arm_global_timer";
clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
CLOCK_EVT_FEAT_PERCPU;
clk->set_mode = gt_clockevent_set_mode;
clk->set_next_event = gt_clockevent_set_next_event;
clk->cpumask = cpumask_of(cpu);
clk->rating = 300;
clk->irq = gt_ppi;
clockevents_config_and_register(clk, gt_clk_rate,
1, 0xffffffff);
enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
return 0;
}
static void gt_clockevents_stop(struct clock_event_device *clk)
{
gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
disable_percpu_irq(clk->irq);
}
static cycle_t gt_clocksource_read(struct clocksource *cs)
{
return gt_counter_read();
}
static struct clocksource gt_clocksource = {
.name = "arm_global_timer",
.rating = 300,
.read = gt_clocksource_read,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
static u64 notrace gt_sched_clock_read(void)
{
return gt_counter_read();
}
#endif
static void __init gt_clocksource_init(void)
{
writel(0, gt_base + GT_CONTROL);
writel(0, gt_base + GT_COUNTER0);
writel(0, gt_base + GT_COUNTER1);
/* enables timer on all the cores */
writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
#endif
clocksource_register_hz(>_clocksource, gt_clk_rate);
}
static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_STARTING:
gt_clockevents_init(this_cpu_ptr(gt_evt));
break;
case CPU_DYING:
gt_clockevents_stop(this_cpu_ptr(gt_evt));
break;
}
return NOTIFY_OK;
}
static struct notifier_block gt_cpu_nb = {
.notifier_call = gt_cpu_notify,
};
static void __init global_timer_of_register(struct device_node *np)
{
struct clk *gt_clk;
int err = 0;
/*
* In r2p0 the comparators for each processor with the global timer
* fire when the timer value is greater than or equal to. In previous
* revisions the comparators fired when the timer value was equal to.
*/
if ((read_cpuid_id() & 0xf0000f) < 0x200000) {
pr_warn("global-timer: non support for this cpu version.\n");
return;
}
gt_ppi = irq_of_parse_and_map(np, 0);
if (!gt_ppi) {
pr_warn("global-timer: unable to parse irq\n");
return;
}
gt_base = of_iomap(np, 0);
if (!gt_base) {
pr_warn("global-timer: invalid base address\n");
return;
}
gt_clk = of_clk_get(np, 0);
if (!IS_ERR(gt_clk)) {
err = clk_prepare_enable(gt_clk);
if (err)
goto out_unmap;
} else {
pr_warn("global-timer: clk not found\n");
err = -EINVAL;
goto out_unmap;
}
gt_clk_rate = clk_get_rate(gt_clk);
gt_evt = alloc_percpu(struct clock_event_device);
if (!gt_evt) {
pr_warn("global-timer: can't allocate memory\n");
err = -ENOMEM;
goto out_clk;
}
err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
"gt", gt_evt);
if (err) {
pr_warn("global-timer: can't register interrupt %d (%d)\n",
gt_ppi, err);
goto out_free;
}
err = register_cpu_notifier(>_cpu_nb);
if (err) {
pr_warn("global-timer: unable to register cpu notifier.\n");
goto out_irq;
}
/* Immediately configure the timer on the boot CPU */
gt_clocksource_init();
gt_clockevents_init(this_cpu_ptr(gt_evt));
return;
out_irq:
free_percpu_irq(gt_ppi, gt_evt);
out_free:
free_percpu(gt_evt);
out_clk:
clk_disable_unprepare(gt_clk);
out_unmap:
iounmap(gt_base);
WARN(err, "ARM Global timer register failed (%d)\n", err);
}
/* Only tested on r2p2 and r3p0 */
CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
global_timer_of_register);