- 根目录:
- drivers
- clocksource
- cadence_ttc_timer.c
/*
* This file contains driver for the Cadence Triple Timer Counter Rev 06
*
* Copyright (C) 2011-2013 Xilinx
*
* based on arch/mips/kernel/time.c timer driver
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/clockchips.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/slab.h>
#include <linux/clk-provider.h>
/*
* This driver configures the 2 16-bit count-up timers as follows:
*
* T1: Timer 1, clocksource for generic timekeeping
* T2: Timer 2, clockevent source for hrtimers
* T3: Timer 3, <unused>
*
* The input frequency to the timer module for emulation is 2.5MHz which is
* common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
* the timers are clocked at 78.125KHz (12.8 us resolution).
* The input frequency to the timer module in silicon is configurable and
* obtained from device tree. The pre-scaler of 32 is used.
*/
/*
* Timer Register Offset Definitions of Timer 1, Increment base address by 4
* and use same offsets for Timer 2
*/
#define TTC_CLK_CNTRL_OFFSET 0x00 /* Clock Control Reg, RW */
#define TTC_CNT_CNTRL_OFFSET 0x0C /* Counter Control Reg, RW */
#define TTC_COUNT_VAL_OFFSET 0x18 /* Counter Value Reg, RO */
#define TTC_INTR_VAL_OFFSET 0x24 /* Interval Count Reg, RW */
#define TTC_ISR_OFFSET 0x54 /* Interrupt Status Reg, RO */
#define TTC_IER_OFFSET 0x60 /* Interrupt Enable Reg, RW */
#define TTC_CNT_CNTRL_DISABLE_MASK 0x1
/*
* Setup the timers to use pre-scaling, using a fixed value for now that will
* work across most input frequency, but it may need to be more dynamic
*/
#define PRESCALE_EXPONENT 11 /* 2 ^ PRESCALE_EXPONENT = PRESCALE */
#define PRESCALE 2048 /* The exponent must match this */
#define CLK_CNTRL_PRESCALE ((PRESCALE_EXPONENT - 1) << 1)
#define CLK_CNTRL_PRESCALE_EN 1
#define CNT_CNTRL_RESET (1 << 4)
/**
* struct ttc_timer - This definition defines local timer structure
*
* @base_addr: Base address of timer
* @clk: Associated clock source
* @clk_rate_change_nb Notifier block for clock rate changes
*/
struct ttc_timer {
void __iomem *base_addr;
struct clk *clk;
struct notifier_block clk_rate_change_nb;
};
#define to_ttc_timer(x) \
container_of(x, struct ttc_timer, clk_rate_change_nb)
struct ttc_timer_clocksource {
struct ttc_timer ttc;
struct clocksource cs;
};
#define to_ttc_timer_clksrc(x) \
container_of(x, struct ttc_timer_clocksource, cs)
struct ttc_timer_clockevent {
struct ttc_timer ttc;
struct clock_event_device ce;
};
#define to_ttc_timer_clkevent(x) \
container_of(x, struct ttc_timer_clockevent, ce)
/**
* ttc_set_interval - Set the timer interval value
*
* @timer: Pointer to the timer instance
* @cycles: Timer interval ticks
**/
static void ttc_set_interval(struct ttc_timer *timer,
unsigned long cycles)
{
u32 ctrl_reg;
/* Disable the counter, set the counter value and re-enable counter */
ctrl_reg = __raw_readl(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
__raw_writel(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);
/*
* Reset the counter (0x10) so that it starts from 0, one-shot
* mode makes this needed for timing to be right.
*/
ctrl_reg |= CNT_CNTRL_RESET;
ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
}
/**
* ttc_clock_event_interrupt - Clock event timer interrupt handler
*
* @irq: IRQ number of the Timer
* @dev_id: void pointer to the ttc_timer instance
*
* returns: Always IRQ_HANDLED - success
**/
static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)
{
struct ttc_timer_clockevent *ttce = dev_id;
struct ttc_timer *timer = &ttce->ttc;
/* Acknowledge the interrupt and call event handler */
__raw_readl(timer->base_addr + TTC_ISR_OFFSET);
ttce->ce.event_handler(&ttce->ce);
return IRQ_HANDLED;
}
/**
* __ttc_clocksource_read - Reads the timer counter register
*
* returns: Current timer counter register value
**/
static cycle_t __ttc_clocksource_read(struct clocksource *cs)
{
struct ttc_timer *timer = &to_ttc_timer_clksrc(cs)->ttc;
return (cycle_t)__raw_readl(timer->base_addr +
TTC_COUNT_VAL_OFFSET);
}
/**
* ttc_set_next_event - Sets the time interval for next event
*
* @cycles: Timer interval ticks
* @evt: Address of clock event instance
*
* returns: Always 0 - success
**/
static int ttc_set_next_event(unsigned long cycles,
struct clock_event_device *evt)
{
struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
struct ttc_timer *timer = &ttce->ttc;
ttc_set_interval(timer, cycles);
return 0;
}
/**
* ttc_set_mode - Sets the mode of timer
*
* @mode: Mode to be set
* @evt: Address of clock event instance
**/
static void ttc_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
struct ttc_timer *timer = &ttce->ttc;
u32 ctrl_reg;
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
ttc_set_interval(timer,
DIV_ROUND_CLOSEST(clk_get_rate(ttce->ttc.clk),
PRESCALE * HZ));
break;
case CLOCK_EVT_MODE_ONESHOT:
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
ctrl_reg = __raw_readl(timer->base_addr +
TTC_CNT_CNTRL_OFFSET);
ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
__raw_writel(ctrl_reg,
timer->base_addr + TTC_CNT_CNTRL_OFFSET);
break;
case CLOCK_EVT_MODE_RESUME:
ctrl_reg = __raw_readl(timer->base_addr +
TTC_CNT_CNTRL_OFFSET);
ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
__raw_writel(ctrl_reg,
timer->base_addr + TTC_CNT_CNTRL_OFFSET);
break;
}
}
static int ttc_rate_change_clocksource_cb(struct notifier_block *nb,
unsigned long event, void *data)
{
struct clk_notifier_data *ndata = data;
struct ttc_timer *ttc = to_ttc_timer(nb);
struct ttc_timer_clocksource *ttccs = container_of(ttc,
struct ttc_timer_clocksource, ttc);
switch (event) {
case POST_RATE_CHANGE:
/*
* Do whatever is necessary to maintain a proper time base
*
* I cannot find a way to adjust the currently used clocksource
* to the new frequency. __clocksource_updatefreq_hz() sounds
* good, but does not work. Not sure what's that missing.
*
* This approach works, but triggers two clocksource switches.
* The first after unregister to clocksource jiffies. And
* another one after the register to the newly registered timer.
*
* Alternatively we could 'waste' another HW timer to ping pong
* between clock sources. That would also use one register and
* one unregister call, but only trigger one clocksource switch
* for the cost of another HW timer used by the OS.
*/
clocksource_unregister(&ttccs->cs);
clocksource_register_hz(&ttccs->cs,
ndata->new_rate / PRESCALE);
/* fall through */
case PRE_RATE_CHANGE:
case ABORT_RATE_CHANGE:
default:
return NOTIFY_DONE;
}
}
static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
{
struct ttc_timer_clocksource *ttccs;
int err;
ttccs = kzalloc(sizeof(*ttccs), GFP_KERNEL);
if (WARN_ON(!ttccs))
return;
ttccs->ttc.clk = clk;
err = clk_prepare_enable(ttccs->ttc.clk);
if (WARN_ON(err)) {
kfree(ttccs);
return;
}
ttccs->ttc.clk_rate_change_nb.notifier_call =
ttc_rate_change_clocksource_cb;
ttccs->ttc.clk_rate_change_nb.next = NULL;
if (clk_notifier_register(ttccs->ttc.clk,
&ttccs->ttc.clk_rate_change_nb))
pr_warn("Unable to register clock notifier.\n");
ttccs->ttc.base_addr = base;
ttccs->cs.name = "ttc_clocksource";
ttccs->cs.rating = 200;
ttccs->cs.read = __ttc_clocksource_read;
ttccs->cs.mask = CLOCKSOURCE_MASK(16);
ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
/*
* Setup the clock source counter to be an incrementing counter
* with no interrupt and it rolls over at 0xFFFF. Pre-scale
* it by 32 also. Let it start running now.
*/
__raw_writel(0x0, ttccs->ttc.base_addr + TTC_IER_OFFSET);
__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
__raw_writel(CNT_CNTRL_RESET,
ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
err = clocksource_register_hz(&ttccs->cs,
clk_get_rate(ttccs->ttc.clk) / PRESCALE);
if (WARN_ON(err)) {
kfree(ttccs);
return;
}
}
static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
unsigned long event, void *data)
{
struct clk_notifier_data *ndata = data;
struct ttc_timer *ttc = to_ttc_timer(nb);
struct ttc_timer_clockevent *ttcce = container_of(ttc,
struct ttc_timer_clockevent, ttc);
switch (event) {
case POST_RATE_CHANGE:
{
unsigned long flags;
/*
* clockevents_update_freq should be called with IRQ disabled on
* the CPU the timer provides events for. The timer we use is
* common to both CPUs, not sure if we need to run on both
* cores.
*/
local_irq_save(flags);
clockevents_update_freq(&ttcce->ce,
ndata->new_rate / PRESCALE);
local_irq_restore(flags);
/* fall through */
}
case PRE_RATE_CHANGE:
case ABORT_RATE_CHANGE:
default:
return NOTIFY_DONE;
}
}
static void __init ttc_setup_clockevent(struct clk *clk,
void __iomem *base, u32 irq)
{
struct ttc_timer_clockevent *ttcce;
int err;
ttcce = kzalloc(sizeof(*ttcce), GFP_KERNEL);
if (WARN_ON(!ttcce))
return;
ttcce->ttc.clk = clk;
err = clk_prepare_enable(ttcce->ttc.clk);
if (WARN_ON(err)) {
kfree(ttcce);
return;
}
ttcce->ttc.clk_rate_change_nb.notifier_call =
ttc_rate_change_clockevent_cb;
ttcce->ttc.clk_rate_change_nb.next = NULL;
if (clk_notifier_register(ttcce->ttc.clk,
&ttcce->ttc.clk_rate_change_nb))
pr_warn("Unable to register clock notifier.\n");
ttcce->ttc.base_addr = base;
ttcce->ce.name = "ttc_clockevent";
ttcce->ce.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
ttcce->ce.set_next_event = ttc_set_next_event;
ttcce->ce.set_mode = ttc_set_mode;
ttcce->ce.rating = 200;
ttcce->ce.irq = irq;
ttcce->ce.cpumask = cpu_possible_mask;
/*
* Setup the clock event timer to be an interval timer which
* is prescaled by 32 using the interval interrupt. Leave it
* disabled for now.
*/
__raw_writel(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
__raw_writel(0x1, ttcce->ttc.base_addr + TTC_IER_OFFSET);
err = request_irq(irq, ttc_clock_event_interrupt,
IRQF_DISABLED | IRQF_TIMER,
ttcce->ce.name, ttcce);
if (WARN_ON(err)) {
kfree(ttcce);
return;
}
clockevents_config_and_register(&ttcce->ce,
clk_get_rate(ttcce->ttc.clk) / PRESCALE, 1, 0xfffe);
}
/**
* ttc_timer_init - Initialize the timer
*
* Initializes the timer hardware and register the clock source and clock event
* timers with Linux kernal timer framework
*/
static void __init ttc_timer_init(struct device_node *timer)
{
unsigned int irq;
void __iomem *timer_baseaddr;
struct clk *clk;
static int initialized;
if (initialized)
return;
initialized = 1;
/*
* Get the 1st Triple Timer Counter (TTC) block from the device tree
* and use it. Note that the event timer uses the interrupt and it's the
* 2nd TTC hence the irq_of_parse_and_map(,1)
*/
timer_baseaddr = of_iomap(timer, 0);
if (!timer_baseaddr) {
pr_err("ERROR: invalid timer base address\n");
BUG();
}
irq = irq_of_parse_and_map(timer, 1);
if (irq <= 0) {
pr_err("ERROR: invalid interrupt number\n");
BUG();
}
clk = of_clk_get_by_name(timer, "cpu_1x");
if (IS_ERR(clk)) {
pr_err("ERROR: timer input clock not found\n");
BUG();
}
ttc_setup_clocksource(clk, timer_baseaddr);
ttc_setup_clockevent(clk, timer_baseaddr + 4, irq);
pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
}
CLOCKSOURCE_OF_DECLARE(ttc, "cdns,ttc", ttc_timer_init);