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timer-atmel-tcb.c
timer-atmel-tcb.c 12.62 KiB
// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>
#include <linux/syscore_ops.h>
#include <soc/at91/atmel_tcb.h>
/*
* We're configured to use a specific TC block, one that's not hooked
* up to external hardware, to provide a time solution:
*
* - Two channels combine to create a free-running 32 bit counter
* with a base rate of 5+ MHz, packaged as a clocksource (with
* resolution better than 200 nsec).
* - Some chips support 32 bit counter. A single channel is used for
* this 32 bit free-running counter. the second channel is not used.
*
* - The third channel may be used to provide a 16-bit clockevent
* source, used in either periodic or oneshot mode. This runs
* at 32 KiHZ, and can handle delays of up to two seconds.
*
* REVISIT behavior during system suspend states... we should disable
* all clocks and save the power. Easily done for clockevent devices,
* but clocksources won't necessarily get the needed notifications.
* For deeper system sleep states, this will be mandatory...
*/
static void __iomem *tcaddr;
static struct
{
u32 cmr;
u32 imr;
u32 rc;
bool clken;
} tcb_cache[3];
static u32 bmr_cache;
static u64 tc_get_cycles(struct clocksource *cs)
{
unsigned long flags;
u32 lower, upper;
raw_local_irq_save(flags);
do {
upper = readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV));
lower = readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
} while (upper != readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV)));
raw_local_irq_restore(flags);
return (upper << 16) | lower;
}
static u64 tc_get_cycles32(struct clocksource *cs)
{
return readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
}
static void tc_clksrc_suspend(struct clocksource *cs)
{ int i;
for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
tcb_cache[i].cmr = readl(tcaddr + ATMEL_TC_REG(i, CMR));
tcb_cache[i].imr = readl(tcaddr + ATMEL_TC_REG(i, IMR));
tcb_cache[i].rc = readl(tcaddr + ATMEL_TC_REG(i, RC));
tcb_cache[i].clken = !!(readl(tcaddr + ATMEL_TC_REG(i, SR)) &
ATMEL_TC_CLKSTA);
}
bmr_cache = readl(tcaddr + ATMEL_TC_BMR);
}
static void tc_clksrc_resume(struct clocksource *cs)
{
int i;
for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
/* Restore registers for the channel, RA and RB are not used */
writel(tcb_cache[i].cmr, tcaddr + ATMEL_TC_REG(i, CMR));
writel(tcb_cache[i].rc, tcaddr + ATMEL_TC_REG(i, RC));
writel(0, tcaddr + ATMEL_TC_REG(i, RA));
writel(0, tcaddr + ATMEL_TC_REG(i, RB));
/* Disable all the interrupts */
writel(0xff, tcaddr + ATMEL_TC_REG(i, IDR));
/* Reenable interrupts that were enabled before suspending */
writel(tcb_cache[i].imr, tcaddr + ATMEL_TC_REG(i, IER));
/* Start the clock if it was used */
if (tcb_cache[i].clken)
writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(i, CCR));
}
/* Dual channel, chain channels */
writel(bmr_cache, tcaddr + ATMEL_TC_BMR);
/* Finally, trigger all the channels*/
writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
}
static struct clocksource clksrc = {
.rating = 200,
.read = tc_get_cycles,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.suspend = tc_clksrc_suspend,
.resume = tc_clksrc_resume,
};
static u64 notrace tc_sched_clock_read(void)
{
return tc_get_cycles(&clksrc);
}
static u64 notrace tc_sched_clock_read32(void)
{
return tc_get_cycles32(&clksrc);
}
#ifdef CONFIG_GENERIC_CLOCKEVENTS
struct tc_clkevt_device {
struct clock_event_device clkevt;
struct clk *clk;
void __iomem *regs;
};
static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
{
return container_of(clkevt, struct tc_clkevt_device, clkevt);
}
/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
* because using one of the divided clocks would usually mean the
* tick rate can never be less than several dozen Hz (vs 0.5 Hz).
*
* A divided clock could be good for high resolution timers, since
* 30.5 usec resolution can seem "low".
*/
static u32 timer_clock;
static int tc_shutdown(struct clock_event_device *d)
{
struct tc_clkevt_device *tcd = to_tc_clkevt(d);
void __iomem *regs = tcd->regs;
writel(0xff, regs + ATMEL_TC_REG(2, IDR));
writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
if (!clockevent_state_detached(d))
clk_disable(tcd->clk);
return 0;
}
static int tc_set_oneshot(struct clock_event_device *d)
{
struct tc_clkevt_device *tcd = to_tc_clkevt(d);
void __iomem *regs = tcd->regs;
if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
tc_shutdown(d);
clk_enable(tcd->clk);
/* slow clock, count up to RC, then irq and stop */
writel(timer_clock | ATMEL_TC_CPCSTOP | ATMEL_TC_WAVE |
ATMEL_TC_WAVESEL_UP_AUTO, regs + ATMEL_TC_REG(2, CMR));
writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
/* set_next_event() configures and starts the timer */
return 0;
}
static int tc_set_periodic(struct clock_event_device *d)
{
struct tc_clkevt_device *tcd = to_tc_clkevt(d);
void __iomem *regs = tcd->regs;
if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
tc_shutdown(d);
/* By not making the gentime core emulate periodic mode on top
* of oneshot, we get lower overhead and improved accuracy.
*/
clk_enable(tcd->clk);
/* slow clock, count up to RC, then irq and restart */
writel(timer_clock | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
writel((32768 + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
/* Enable clock and interrupts on RC compare */
writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
/* go go gadget! */
writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG, regs +
ATMEL_TC_REG(2, CCR));
return 0;
}
static int tc_next_event(unsigned long delta, struct clock_event_device *d)
{ writel_relaxed(delta, tcaddr + ATMEL_TC_REG(2, RC));
/* go go gadget! */
writel_relaxed(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
tcaddr + ATMEL_TC_REG(2, CCR));
return 0;
}
static struct tc_clkevt_device clkevt = {
.clkevt = {
.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT,
/* Should be lower than at91rm9200's system timer */
.rating = 125,
.set_next_event = tc_next_event,
.set_state_shutdown = tc_shutdown,
.set_state_periodic = tc_set_periodic,
.set_state_oneshot = tc_set_oneshot,
},
};
static irqreturn_t ch2_irq(int irq, void *handle)
{
struct tc_clkevt_device *dev = handle;
unsigned int sr;
sr = readl_relaxed(dev->regs + ATMEL_TC_REG(2, SR));
if (sr & ATMEL_TC_CPCS) {
dev->clkevt.event_handler(&dev->clkevt);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
int ret;
struct clk *t2_clk = tc->clk[2];
int irq = tc->irq[2];
ret = clk_prepare_enable(tc->slow_clk);
if (ret)
return ret;
/* try to enable t2 clk to avoid future errors in mode change */
ret = clk_prepare_enable(t2_clk);
if (ret) {
clk_disable_unprepare(tc->slow_clk);
return ret;
}
clk_disable(t2_clk);
clkevt.regs = tc->regs;
clkevt.clk = t2_clk;
timer_clock = clk32k_divisor_idx;
clkevt.clkevt.cpumask = cpumask_of(0);
ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
if (ret) {
clk_unprepare(t2_clk);
clk_disable_unprepare(tc->slow_clk);
return ret;
}
clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
return ret;
}
#else /* !CONFIG_GENERIC_CLOCKEVENTS */
static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
/* NOTHING */
return 0;
}
#endif
static void __init tcb_setup_dual_chan(struct atmel_tc *tc, int mck_divisor_idx)
{
/* channel 0: waveform mode, input mclk/8, clock TIOA0 on overflow */
writel(mck_divisor_idx /* likely divide-by-8 */
| ATMEL_TC_WAVE
| ATMEL_TC_WAVESEL_UP /* free-run */
| ATMEL_TC_ACPA_SET /* TIOA0 rises at 0 */
| ATMEL_TC_ACPC_CLEAR, /* (duty cycle 50%) */
tcaddr + ATMEL_TC_REG(0, CMR));
writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
/* channel 1: waveform mode, input TIOA0 */
writel(ATMEL_TC_XC1 /* input: TIOA0 */
| ATMEL_TC_WAVE
| ATMEL_TC_WAVESEL_UP, /* free-run */
tcaddr + ATMEL_TC_REG(1, CMR));
writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR)); /* no irqs */
writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
/* chain channel 0 to channel 1*/
writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
/* then reset all the timers */
writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
}
static void __init tcb_setup_single_chan(struct atmel_tc *tc, int mck_divisor_idx)
{
/* channel 0: waveform mode, input mclk/8 */
writel(mck_divisor_idx /* likely divide-by-8 */
| ATMEL_TC_WAVE
| ATMEL_TC_WAVESEL_UP, /* free-run */
tcaddr + ATMEL_TC_REG(0, CMR));
writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
/* then reset all the timers */
writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
}
static const u8 atmel_tcb_divisors[5] = { 2, 8, 32, 128, 0, };
static const struct of_device_id atmel_tcb_of_match[] = {
{ .compatible = "atmel,at91rm9200-tcb", .data = (void *)16, },
{ .compatible = "atmel,at91sam9x5-tcb", .data = (void *)32, },
{ /* sentinel */ }
};
static int __init tcb_clksrc_init(struct device_node *node)
{
struct atmel_tc tc;
struct clk *t0_clk;
const struct of_device_id *match;
u64 (*tc_sched_clock)(void);
u32 rate, divided_rate = 0; int best_divisor_idx = -1;
int clk32k_divisor_idx = -1;
int bits;
int i;
int ret;
/* Protect against multiple calls */
if (tcaddr)
return 0;
tc.regs = of_iomap(node->parent, 0);
if (!tc.regs)
return -ENXIO;
t0_clk = of_clk_get_by_name(node->parent, "t0_clk");
if (IS_ERR(t0_clk))
return PTR_ERR(t0_clk);
tc.slow_clk = of_clk_get_by_name(node->parent, "slow_clk");
if (IS_ERR(tc.slow_clk))
return PTR_ERR(tc.slow_clk);
tc.clk[0] = t0_clk;
tc.clk[1] = of_clk_get_by_name(node->parent, "t1_clk");
if (IS_ERR(tc.clk[1]))
tc.clk[1] = t0_clk;
tc.clk[2] = of_clk_get_by_name(node->parent, "t2_clk");
if (IS_ERR(tc.clk[2]))
tc.clk[2] = t0_clk;
tc.irq[2] = of_irq_get(node->parent, 2);
if (tc.irq[2] <= 0) {
tc.irq[2] = of_irq_get(node->parent, 0);
if (tc.irq[2] <= 0)
return -EINVAL;
}
match = of_match_node(atmel_tcb_of_match, node->parent);
bits = (uintptr_t)match->data;
for (i = 0; i < ARRAY_SIZE(tc.irq); i++)
writel(ATMEL_TC_ALL_IRQ, tc.regs + ATMEL_TC_REG(i, IDR));
ret = clk_prepare_enable(t0_clk);
if (ret) {
pr_debug("can't enable T0 clk\n");
return ret;
}
/* How fast will we be counting? Pick something over 5 MHz. */
rate = (u32) clk_get_rate(t0_clk);
for (i = 0; i < ARRAY_SIZE(atmel_tcb_divisors); i++) {
unsigned divisor = atmel_tcb_divisors[i];
unsigned tmp;
/* remember 32 KiHz clock for later */
if (!divisor) {
clk32k_divisor_idx = i;
continue;
}
tmp = rate / divisor;
pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
if (best_divisor_idx > 0) {
if (tmp < 5 * 1000 * 1000)
continue;
}
divided_rate = tmp;
best_divisor_idx = i;
}
clksrc.name = kbasename(node->parent->full_name);
clkevt.clkevt.name = kbasename(node->parent->full_name);
pr_debug("%s at %d.%03d MHz\n", clksrc.name, divided_rate / 1000000,
((divided_rate % 1000000) + 500) / 1000);
tcaddr = tc.regs;
if (bits == 32) {
/* use apropriate function to read 32 bit counter */
clksrc.read = tc_get_cycles32;
/* setup ony channel 0 */
tcb_setup_single_chan(&tc, best_divisor_idx);
tc_sched_clock = tc_sched_clock_read32;
} else {
/* we have three clocks no matter what the
* underlying platform supports.
*/
ret = clk_prepare_enable(tc.clk[1]);
if (ret) {
pr_debug("can't enable T1 clk\n");
goto err_disable_t0;
}
/* setup both channel 0 & 1 */
tcb_setup_dual_chan(&tc, best_divisor_idx);
tc_sched_clock = tc_sched_clock_read;
}
/* and away we go! */
ret = clocksource_register_hz(&clksrc, divided_rate);
if (ret)
goto err_disable_t1;
/* channel 2: periodic and oneshot timer support */
ret = setup_clkevents(&tc, clk32k_divisor_idx);
if (ret)
goto err_unregister_clksrc;
sched_clock_register(tc_sched_clock, 32, divided_rate);
return 0;
err_unregister_clksrc:
clocksource_unregister(&clksrc);
err_disable_t1:
if (bits != 32)
clk_disable_unprepare(tc.clk[1]);
err_disable_t0:
clk_disable_unprepare(t0_clk);
tcaddr = NULL;
return ret;
}
TIMER_OF_DECLARE(atmel_tcb_clksrc, "atmel,tcb-timer", tcb_clksrc_init);