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linux/drivers/clocksource/timer-fttmr010.c
Tao Ren 4451d3f59f clocksource/drivers/fttmr010: Fix set_next_event handler 
Currently, the aspeed MATCH1 register is updated to <current_count -
cycles> in set_next_event handler, with the assumption that COUNT
register value is preserved when the timer is disabled and it continues
decrementing after the timer is enabled. But the assumption is wrong:
RELOAD register is loaded into COUNT register when the aspeed timer is
enabled, which means the next event may be delayed because timer
interrupt won't be generated until <0xFFFFFFFF - current_count +
cycles>.

The problem can be fixed by updating RELOAD register to <cycles>, and
COUNT register will be re-loaded when the timer is enabled and interrupt
is generated when COUNT register overflows.

The test result on Facebook Backpack-CMM BMC hardware (AST2500) shows
the issue is fixed: without the patch, usleep(100) suspends the process
for several milliseconds (and sometimes even over 40 milliseconds);
after applying the fix, usleep(100) takes averagely 240 microseconds to
return under the same workload level.

Signed-off-by: Tao Ren <taoren@fb.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Lei YU <mine260309@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
2018-09-24 06:13:31 +02:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Faraday Technology FTTMR010 timer driver
* Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
*
* Based on a rewrite of arch/arm/mach-gemini/timer.c:
* Copyright (C) 2001-2006 Storlink, Corp.
* Copyright (C) 2008-2009 Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
*/
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/sched_clock.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/delay.h>
/*
* Register definitions for the timers
*/
#define TIMER1_COUNT (0x00)
#define TIMER1_LOAD (0x04)
#define TIMER1_MATCH1 (0x08)
#define TIMER1_MATCH2 (0x0c)
#define TIMER2_COUNT (0x10)
#define TIMER2_LOAD (0x14)
#define TIMER2_MATCH1 (0x18)
#define TIMER2_MATCH2 (0x1c)
#define TIMER3_COUNT (0x20)
#define TIMER3_LOAD (0x24)
#define TIMER3_MATCH1 (0x28)
#define TIMER3_MATCH2 (0x2c)
#define TIMER_CR (0x30)
#define TIMER_INTR_STATE (0x34)
#define TIMER_INTR_MASK (0x38)
#define TIMER_1_CR_ENABLE BIT(0)
#define TIMER_1_CR_CLOCK BIT(1)
#define TIMER_1_CR_INT BIT(2)
#define TIMER_2_CR_ENABLE BIT(3)
#define TIMER_2_CR_CLOCK BIT(4)
#define TIMER_2_CR_INT BIT(5)
#define TIMER_3_CR_ENABLE BIT(6)
#define TIMER_3_CR_CLOCK BIT(7)
#define TIMER_3_CR_INT BIT(8)
#define TIMER_1_CR_UPDOWN BIT(9)
#define TIMER_2_CR_UPDOWN BIT(10)
#define TIMER_3_CR_UPDOWN BIT(11)
/*
* The Aspeed AST2400 moves bits around in the control register
* and lacks bits for setting the timer to count upwards.
*/
#define TIMER_1_CR_ASPEED_ENABLE BIT(0)
#define TIMER_1_CR_ASPEED_CLOCK BIT(1)
#define TIMER_1_CR_ASPEED_INT BIT(2)
#define TIMER_2_CR_ASPEED_ENABLE BIT(4)
#define TIMER_2_CR_ASPEED_CLOCK BIT(5)
#define TIMER_2_CR_ASPEED_INT BIT(6)
#define TIMER_3_CR_ASPEED_ENABLE BIT(8)
#define TIMER_3_CR_ASPEED_CLOCK BIT(9)
#define TIMER_3_CR_ASPEED_INT BIT(10)
#define TIMER_1_INT_MATCH1 BIT(0)
#define TIMER_1_INT_MATCH2 BIT(1)
#define TIMER_1_INT_OVERFLOW BIT(2)
#define TIMER_2_INT_MATCH1 BIT(3)
#define TIMER_2_INT_MATCH2 BIT(4)
#define TIMER_2_INT_OVERFLOW BIT(5)
#define TIMER_3_INT_MATCH1 BIT(6)
#define TIMER_3_INT_MATCH2 BIT(7)
#define TIMER_3_INT_OVERFLOW BIT(8)
#define TIMER_INT_ALL_MASK 0x1ff
struct fttmr010 {
void __iomem *base;
unsigned int tick_rate;
bool count_down;
u32 t1_enable_val;
struct clock_event_device clkevt;
#ifdef CONFIG_ARM
struct delay_timer delay_timer;
#endif
};
/*
* A local singleton used by sched_clock and delay timer reads, which are
* fast and stateless
*/
static struct fttmr010 *local_fttmr;
static inline struct fttmr010 *to_fttmr010(struct clock_event_device *evt)
{
return container_of(evt, struct fttmr010, clkevt);
}
static unsigned long fttmr010_read_current_timer_up(void)
{
return readl(local_fttmr->base + TIMER2_COUNT);
}
static unsigned long fttmr010_read_current_timer_down(void)
{
return ~readl(local_fttmr->base + TIMER2_COUNT);
}
static u64 notrace fttmr010_read_sched_clock_up(void)
{
return fttmr010_read_current_timer_up();
}
static u64 notrace fttmr010_read_sched_clock_down(void)
{
return fttmr010_read_current_timer_down();
}
static int fttmr010_timer_set_next_event(unsigned long cycles,
struct clock_event_device *evt)
{
struct fttmr010 *fttmr010 = to_fttmr010(evt);
u32 cr;
/* Stop */
cr = readl(fttmr010->base + TIMER_CR);
cr &= ~fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
if (fttmr010->count_down) {
/*
* ASPEED Timer Controller will load TIMER1_LOAD register
* into TIMER1_COUNT register when the timer is re-enabled.
*/
writel(cycles, fttmr010->base + TIMER1_LOAD);
} else {
/* Setup the match register forward in time */
cr = readl(fttmr010->base + TIMER1_COUNT);
writel(cr + cycles, fttmr010->base + TIMER1_MATCH1);
}
/* Start */
cr = readl(fttmr010->base + TIMER_CR);
cr |= fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
return 0;
}
static int fttmr010_timer_shutdown(struct clock_event_device *evt)
{
struct fttmr010 *fttmr010 = to_fttmr010(evt);
u32 cr;
/* Stop */
cr = readl(fttmr010->base + TIMER_CR);
cr &= ~fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
return 0;
}
static int fttmr010_timer_set_oneshot(struct clock_event_device *evt)
{
struct fttmr010 *fttmr010 = to_fttmr010(evt);
u32 cr;
/* Stop */
cr = readl(fttmr010->base + TIMER_CR);
cr &= ~fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
/* Setup counter start from 0 or ~0 */
writel(0, fttmr010->base + TIMER1_COUNT);
if (fttmr010->count_down)
writel(~0, fttmr010->base + TIMER1_LOAD);
else
writel(0, fttmr010->base + TIMER1_LOAD);
/* Enable interrupt */
cr = readl(fttmr010->base + TIMER_INTR_MASK);
cr &= ~(TIMER_1_INT_OVERFLOW | TIMER_1_INT_MATCH2);
cr |= TIMER_1_INT_MATCH1;
writel(cr, fttmr010->base + TIMER_INTR_MASK);
return 0;
}
static int fttmr010_timer_set_periodic(struct clock_event_device *evt)
{
struct fttmr010 *fttmr010 = to_fttmr010(evt);
u32 period = DIV_ROUND_CLOSEST(fttmr010->tick_rate, HZ);
u32 cr;
/* Stop */
cr = readl(fttmr010->base + TIMER_CR);
cr &= ~fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
/* Setup timer to fire at 1/HZ intervals. */
if (fttmr010->count_down) {
writel(period, fttmr010->base + TIMER1_LOAD);
writel(0, fttmr010->base + TIMER1_MATCH1);
} else {
cr = 0xffffffff - (period - 1);
writel(cr, fttmr010->base + TIMER1_COUNT);
writel(cr, fttmr010->base + TIMER1_LOAD);
/* Enable interrupt on overflow */
cr = readl(fttmr010->base + TIMER_INTR_MASK);
cr &= ~(TIMER_1_INT_MATCH1 | TIMER_1_INT_MATCH2);
cr |= TIMER_1_INT_OVERFLOW;
writel(cr, fttmr010->base + TIMER_INTR_MASK);
}
/* Start the timer */
cr = readl(fttmr010->base + TIMER_CR);
cr |= fttmr010->t1_enable_val;
writel(cr, fttmr010->base + TIMER_CR);
return 0;
}
/*
* IRQ handler for the timer
*/
static irqreturn_t fttmr010_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = dev_id;
evt->event_handler(evt);
return IRQ_HANDLED;
}
static int __init fttmr010_common_init(struct device_node *np, bool is_aspeed)
{
struct fttmr010 *fttmr010;
int irq;
struct clk *clk;
int ret;
u32 val;
/*
* These implementations require a clock reference.
* FIXME: we currently only support clocking using PCLK
* and using EXTCLK is not supported in the driver.
*/
clk = of_clk_get_by_name(np, "PCLK");
if (IS_ERR(clk)) {
pr_err("could not get PCLK\n");
return PTR_ERR(clk);
}
ret = clk_prepare_enable(clk);
if (ret) {
pr_err("failed to enable PCLK\n");
return ret;
}
fttmr010 = kzalloc(sizeof(*fttmr010), GFP_KERNEL);
if (!fttmr010) {
ret = -ENOMEM;
goto out_disable_clock;
}
fttmr010->tick_rate = clk_get_rate(clk);
fttmr010->base = of_iomap(np, 0);
if (!fttmr010->base) {
pr_err("Can't remap registers\n");
ret = -ENXIO;
goto out_free;
}
/* IRQ for timer 1 */
irq = irq_of_parse_and_map(np, 0);
if (irq <= 0) {
pr_err("Can't parse IRQ\n");
ret = -EINVAL;
goto out_unmap;
}
/*
* The Aspeed AST2400 moves bits around in the control register,
* otherwise it works the same.
*/
if (is_aspeed) {
fttmr010->t1_enable_val = TIMER_1_CR_ASPEED_ENABLE |
TIMER_1_CR_ASPEED_INT;
/* Downward not available */
fttmr010->count_down = true;
} else {
fttmr010->t1_enable_val = TIMER_1_CR_ENABLE | TIMER_1_CR_INT;
}
/*
* Reset the interrupt mask and status
*/
writel(TIMER_INT_ALL_MASK, fttmr010->base + TIMER_INTR_MASK);
writel(0, fttmr010->base + TIMER_INTR_STATE);
/*
* Enable timer 1 count up, timer 2 count up, except on Aspeed,
* where everything just counts down.
*/
if (is_aspeed)
val = TIMER_2_CR_ASPEED_ENABLE;
else {
val = TIMER_2_CR_ENABLE;
if (!fttmr010->count_down)
val |= TIMER_1_CR_UPDOWN | TIMER_2_CR_UPDOWN;
}
writel(val, fttmr010->base + TIMER_CR);
/*
* Setup free-running clocksource timer (interrupts
* disabled.)
*/
local_fttmr = fttmr010;
writel(0, fttmr010->base + TIMER2_COUNT);
writel(0, fttmr010->base + TIMER2_MATCH1);
writel(0, fttmr010->base + TIMER2_MATCH2);
if (fttmr010->count_down) {
writel(~0, fttmr010->base + TIMER2_LOAD);
clocksource_mmio_init(fttmr010->base + TIMER2_COUNT,
"FTTMR010-TIMER2",
fttmr010->tick_rate,
300, 32, clocksource_mmio_readl_down);
sched_clock_register(fttmr010_read_sched_clock_down, 32,
fttmr010->tick_rate);
} else {
writel(0, fttmr010->base + TIMER2_LOAD);
clocksource_mmio_init(fttmr010->base + TIMER2_COUNT,
"FTTMR010-TIMER2",
fttmr010->tick_rate,
300, 32, clocksource_mmio_readl_up);
sched_clock_register(fttmr010_read_sched_clock_up, 32,
fttmr010->tick_rate);
}
/*
* Setup clockevent timer (interrupt-driven) on timer 1.
*/
writel(0, fttmr010->base + TIMER1_COUNT);
writel(0, fttmr010->base + TIMER1_LOAD);
writel(0, fttmr010->base + TIMER1_MATCH1);
writel(0, fttmr010->base + TIMER1_MATCH2);
ret = request_irq(irq, fttmr010_timer_interrupt, IRQF_TIMER,
"FTTMR010-TIMER1", &fttmr010->clkevt);
if (ret) {
pr_err("FTTMR010-TIMER1 no IRQ\n");
goto out_unmap;
}
fttmr010->clkevt.name = "FTTMR010-TIMER1";
/* Reasonably fast and accurate clock event */
fttmr010->clkevt.rating = 300;
fttmr010->clkevt.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT;
fttmr010->clkevt.set_next_event = fttmr010_timer_set_next_event;
fttmr010->clkevt.set_state_shutdown = fttmr010_timer_shutdown;
fttmr010->clkevt.set_state_periodic = fttmr010_timer_set_periodic;
fttmr010->clkevt.set_state_oneshot = fttmr010_timer_set_oneshot;
fttmr010->clkevt.tick_resume = fttmr010_timer_shutdown;
fttmr010->clkevt.cpumask = cpumask_of(0);
fttmr010->clkevt.irq = irq;
clockevents_config_and_register(&fttmr010->clkevt,
fttmr010->tick_rate,
1, 0xffffffff);
#ifdef CONFIG_ARM
/* Also use this timer for delays */
if (fttmr010->count_down)
fttmr010->delay_timer.read_current_timer =
fttmr010_read_current_timer_down;
else
fttmr010->delay_timer.read_current_timer =
fttmr010_read_current_timer_up;
fttmr010->delay_timer.freq = fttmr010->tick_rate;
register_current_timer_delay(&fttmr010->delay_timer);
#endif
return 0;
out_unmap:
iounmap(fttmr010->base);
out_free:
kfree(fttmr010);
out_disable_clock:
clk_disable_unprepare(clk);
return ret;
}
static __init int aspeed_timer_init(struct device_node *np)
{
return fttmr010_common_init(np, true);
}
static __init int fttmr010_timer_init(struct device_node *np)
{
return fttmr010_common_init(np, false);
}
TIMER_OF_DECLARE(fttmr010, "faraday,fttmr010", fttmr010_timer_init);
TIMER_OF_DECLARE(gemini, "cortina,gemini-timer", fttmr010_timer_init);
TIMER_OF_DECLARE(moxart, "moxa,moxart-timer", fttmr010_timer_init);
TIMER_OF_DECLARE(ast2400, "aspeed,ast2400-timer", aspeed_timer_init);
TIMER_OF_DECLARE(ast2500, "aspeed,ast2500-timer", aspeed_timer_init);
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