remarkable-linux/drivers/clocksource/sun4i_timer.c
Chen-Yu Tsai b53e7d000d clocksource/drivers/sun4i: Clear interrupts after stopping timer in probe function
The bootloader (U-boot) sometimes uses this timer for various delays.
It uses it as a ongoing counter, and does comparisons on the current
counter value. The timer counter is never stopped.

In some cases when the user interacts with the bootloader, or lets
it idle for some time before loading Linux, the timer may expire,
and an interrupt will be pending. This results in an unexpected
interrupt when the timer interrupt is enabled by the kernel, at
which point the event_handler isn't set yet. This results in a NULL
pointer dereference exception, panic, and no way to reboot.

Clear any pending interrupts after we stop the timer in the probe
function to avoid this.

Cc: stable@vger.kernel.org
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
2016-08-26 15:56:01 +02:00

238 lines
6 KiB
C

/*
* Allwinner A1X SoCs timer handling.
*
* Copyright (C) 2012 Maxime Ripard
*
* Maxime Ripard <maxime.ripard@free-electrons.com>
*
* Based on code from
* Allwinner Technology Co., Ltd. <www.allwinnertech.com>
* Benn Huang <benn@allwinnertech.com>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irqreturn.h>
#include <linux/sched_clock.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#define TIMER_IRQ_EN_REG 0x00
#define TIMER_IRQ_EN(val) BIT(val)
#define TIMER_IRQ_ST_REG 0x04
#define TIMER_CTL_REG(val) (0x10 * val + 0x10)
#define TIMER_CTL_ENABLE BIT(0)
#define TIMER_CTL_RELOAD BIT(1)
#define TIMER_CTL_CLK_SRC(val) (((val) & 0x3) << 2)
#define TIMER_CTL_CLK_SRC_OSC24M (1)
#define TIMER_CTL_CLK_PRES(val) (((val) & 0x7) << 4)
#define TIMER_CTL_ONESHOT BIT(7)
#define TIMER_INTVAL_REG(val) (0x10 * (val) + 0x14)
#define TIMER_CNTVAL_REG(val) (0x10 * (val) + 0x18)
#define TIMER_SYNC_TICKS 3
static void __iomem *timer_base;
static u32 ticks_per_jiffy;
/*
* When we disable a timer, we need to wait at least for 2 cycles of
* the timer source clock. We will use for that the clocksource timer
* that is already setup and runs at the same frequency than the other
* timers, and we never will be disabled.
*/
static void sun4i_clkevt_sync(void)
{
u32 old = readl(timer_base + TIMER_CNTVAL_REG(1));
while ((old - readl(timer_base + TIMER_CNTVAL_REG(1))) < TIMER_SYNC_TICKS)
cpu_relax();
}
static void sun4i_clkevt_time_stop(u8 timer)
{
u32 val = readl(timer_base + TIMER_CTL_REG(timer));
writel(val & ~TIMER_CTL_ENABLE, timer_base + TIMER_CTL_REG(timer));
sun4i_clkevt_sync();
}
static void sun4i_clkevt_time_setup(u8 timer, unsigned long delay)
{
writel(delay, timer_base + TIMER_INTVAL_REG(timer));
}
static void sun4i_clkevt_time_start(u8 timer, bool periodic)
{
u32 val = readl(timer_base + TIMER_CTL_REG(timer));
if (periodic)
val &= ~TIMER_CTL_ONESHOT;
else
val |= TIMER_CTL_ONESHOT;
writel(val | TIMER_CTL_ENABLE | TIMER_CTL_RELOAD,
timer_base + TIMER_CTL_REG(timer));
}
static int sun4i_clkevt_shutdown(struct clock_event_device *evt)
{
sun4i_clkevt_time_stop(0);
return 0;
}
static int sun4i_clkevt_set_oneshot(struct clock_event_device *evt)
{
sun4i_clkevt_time_stop(0);
sun4i_clkevt_time_start(0, false);
return 0;
}
static int sun4i_clkevt_set_periodic(struct clock_event_device *evt)
{
sun4i_clkevt_time_stop(0);
sun4i_clkevt_time_setup(0, ticks_per_jiffy);
sun4i_clkevt_time_start(0, true);
return 0;
}
static int sun4i_clkevt_next_event(unsigned long evt,
struct clock_event_device *unused)
{
sun4i_clkevt_time_stop(0);
sun4i_clkevt_time_setup(0, evt - TIMER_SYNC_TICKS);
sun4i_clkevt_time_start(0, false);
return 0;
}
static struct clock_event_device sun4i_clockevent = {
.name = "sun4i_tick",
.rating = 350,
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_state_shutdown = sun4i_clkevt_shutdown,
.set_state_periodic = sun4i_clkevt_set_periodic,
.set_state_oneshot = sun4i_clkevt_set_oneshot,
.tick_resume = sun4i_clkevt_shutdown,
.set_next_event = sun4i_clkevt_next_event,
};
static void sun4i_timer_clear_interrupt(void)
{
writel(TIMER_IRQ_EN(0), timer_base + TIMER_IRQ_ST_REG);
}
static irqreturn_t sun4i_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = (struct clock_event_device *)dev_id;
sun4i_timer_clear_interrupt();
evt->event_handler(evt);
return IRQ_HANDLED;
}
static struct irqaction sun4i_timer_irq = {
.name = "sun4i_timer0",
.flags = IRQF_TIMER | IRQF_IRQPOLL,
.handler = sun4i_timer_interrupt,
.dev_id = &sun4i_clockevent,
};
static u64 notrace sun4i_timer_sched_read(void)
{
return ~readl(timer_base + TIMER_CNTVAL_REG(1));
}
static int __init sun4i_timer_init(struct device_node *node)
{
unsigned long rate = 0;
struct clk *clk;
int ret, irq;
u32 val;
timer_base = of_iomap(node, 0);
if (!timer_base) {
pr_crit("Can't map registers");
return -ENXIO;
}
irq = irq_of_parse_and_map(node, 0);
if (irq <= 0) {
pr_crit("Can't parse IRQ");
return -EINVAL;
}
clk = of_clk_get(node, 0);
if (IS_ERR(clk)) {
pr_crit("Can't get timer clock");
return PTR_ERR(clk);
}
ret = clk_prepare_enable(clk);
if (ret) {
pr_err("Failed to prepare clock");
return ret;
}
rate = clk_get_rate(clk);
writel(~0, timer_base + TIMER_INTVAL_REG(1));
writel(TIMER_CTL_ENABLE | TIMER_CTL_RELOAD |
TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
timer_base + TIMER_CTL_REG(1));
/*
* sched_clock_register does not have priorities, and on sun6i and
* later there is a better sched_clock registered by arm_arch_timer.c
*/
if (of_machine_is_compatible("allwinner,sun4i-a10") ||
of_machine_is_compatible("allwinner,sun5i-a13") ||
of_machine_is_compatible("allwinner,sun5i-a10s"))
sched_clock_register(sun4i_timer_sched_read, 32, rate);
ret = clocksource_mmio_init(timer_base + TIMER_CNTVAL_REG(1), node->name,
rate, 350, 32, clocksource_mmio_readl_down);
if (ret) {
pr_err("Failed to register clocksource");
return ret;
}
ticks_per_jiffy = DIV_ROUND_UP(rate, HZ);
writel(TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
timer_base + TIMER_CTL_REG(0));
/* Make sure timer is stopped before playing with interrupts */
sun4i_clkevt_time_stop(0);
/* clear timer0 interrupt */
sun4i_timer_clear_interrupt();
sun4i_clockevent.cpumask = cpu_possible_mask;
sun4i_clockevent.irq = irq;
clockevents_config_and_register(&sun4i_clockevent, rate,
TIMER_SYNC_TICKS, 0xffffffff);
ret = setup_irq(irq, &sun4i_timer_irq);
if (ret) {
pr_err("failed to setup irq %d\n", irq);
return ret;
}
/* Enable timer0 interrupt */
val = readl(timer_base + TIMER_IRQ_EN_REG);
writel(val | TIMER_IRQ_EN(0), timer_base + TIMER_IRQ_EN_REG);
return ret;
}
CLOCKSOURCE_OF_DECLARE(sun4i, "allwinner,sun4i-a10-timer",
sun4i_timer_init);