linux/drivers/clocksource/tcb_clksrc.c
Nicolas Ferre 8e315a7b0c ARM: at91/tc/clocksource: Add 32 bit variant to Timer Counter
Some SoC have a 32 bit variant of Timer Counter Blocks. We do not
need the chaining of two 16 bit counters anymore for them.

The SoC nature is deduced from the device tree "compatible" string.
For non-device-tree configurations, backward compatibility is maintained
by using the default 16 bit counter configuration.

This patch addresses both the atmel_tclib and its user: tcb_clksrc
clocksource.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
2012-03-01 13:38:49 +01:00

334 lines
9.4 KiB
C

#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/platform_device.h>
#include <linux/atmel_tc.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.
*
* A boot clocksource and clockevent source are also currently needed,
* unless the relevant platforms (ARM/AT91, AVR32/AT32) are changed so
* this code can be used when init_timers() is called, well before most
* devices are set up. (Some low end AT91 parts, which can run uClinux,
* have only the timers in one TC block... they currently don't support
* the tclib code, because of that initialization issue.)
*
* 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 cycle_t tc_get_cycles(struct clocksource *cs)
{
unsigned long flags;
u32 lower, upper;
raw_local_irq_save(flags);
do {
upper = __raw_readl(tcaddr + ATMEL_TC_REG(1, CV));
lower = __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));
} while (upper != __raw_readl(tcaddr + ATMEL_TC_REG(1, CV)));
raw_local_irq_restore(flags);
return (upper << 16) | lower;
}
static cycle_t tc_get_cycles32(struct clocksource *cs)
{
return __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));
}
static struct clocksource clksrc = {
.name = "tcb_clksrc",
.rating = 200,
.read = tc_get_cycles,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#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 void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
{
struct tc_clkevt_device *tcd = to_tc_clkevt(d);
void __iomem *regs = tcd->regs;
if (tcd->clkevt.mode == CLOCK_EVT_MODE_PERIODIC
|| tcd->clkevt.mode == CLOCK_EVT_MODE_ONESHOT) {
__raw_writel(0xff, regs + ATMEL_TC_REG(2, IDR));
__raw_writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
clk_disable(tcd->clk);
}
switch (m) {
/* By not making the gentime core emulate periodic mode on top
* of oneshot, we get lower overhead and improved accuracy.
*/
case CLOCK_EVT_MODE_PERIODIC:
clk_enable(tcd->clk);
/* slow clock, count up to RC, then irq and restart */
__raw_writel(timer_clock
| ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
__raw_writel((32768 + HZ/2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
/* Enable clock and interrupts on RC compare */
__raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
/* go go gadget! */
__raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
regs + ATMEL_TC_REG(2, CCR));
break;
case CLOCK_EVT_MODE_ONESHOT:
clk_enable(tcd->clk);
/* slow clock, count up to RC, then irq and stop */
__raw_writel(timer_clock | ATMEL_TC_CPCSTOP
| ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
regs + ATMEL_TC_REG(2, CMR));
__raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
/* set_next_event() configures and starts the timer */
break;
default:
break;
}
}
static int tc_next_event(unsigned long delta, struct clock_event_device *d)
{
__raw_writel(delta, tcaddr + ATMEL_TC_REG(2, RC));
/* go go gadget! */
__raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
tcaddr + ATMEL_TC_REG(2, CCR));
return 0;
}
static struct tc_clkevt_device clkevt = {
.clkevt = {
.name = "tc_clkevt",
.features = CLOCK_EVT_FEAT_PERIODIC
| CLOCK_EVT_FEAT_ONESHOT,
.shift = 32,
/* Should be lower than at91rm9200's system timer */
.rating = 125,
.set_next_event = tc_next_event,
.set_mode = tc_mode,
},
};
static irqreturn_t ch2_irq(int irq, void *handle)
{
struct tc_clkevt_device *dev = handle;
unsigned int sr;
sr = __raw_readl(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 struct irqaction tc_irqaction = {
.name = "tc_clkevt",
.flags = IRQF_TIMER | IRQF_DISABLED,
.handler = ch2_irq,
};
static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
struct clk *t2_clk = tc->clk[2];
int irq = tc->irq[2];
clkevt.regs = tc->regs;
clkevt.clk = t2_clk;
tc_irqaction.dev_id = &clkevt;
timer_clock = clk32k_divisor_idx;
clkevt.clkevt.mult = div_sc(32768, NSEC_PER_SEC, clkevt.clkevt.shift);
clkevt.clkevt.max_delta_ns
= clockevent_delta2ns(0xffff, &clkevt.clkevt);
clkevt.clkevt.min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;
clkevt.clkevt.cpumask = cpumask_of(0);
clockevents_register_device(&clkevt.clkevt);
setup_irq(irq, &tc_irqaction);
}
#else /* !CONFIG_GENERIC_CLOCKEVENTS */
static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
/* NOTHING */
}
#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 */
__raw_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));
__raw_writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
__raw_writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
__raw_writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
__raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
/* channel 1: waveform mode, input TIOA0 */
__raw_writel(ATMEL_TC_XC1 /* input: TIOA0 */
| ATMEL_TC_WAVE
| ATMEL_TC_WAVESEL_UP, /* free-run */
tcaddr + ATMEL_TC_REG(1, CMR));
__raw_writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR)); /* no irqs */
__raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
/* chain channel 0 to channel 1*/
__raw_writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
/* then reset all the timers */
__raw_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 */
__raw_writel(mck_divisor_idx /* likely divide-by-8 */
| ATMEL_TC_WAVE
| ATMEL_TC_WAVESEL_UP, /* free-run */
tcaddr + ATMEL_TC_REG(0, CMR));
__raw_writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
__raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
/* then reset all the timers */
__raw_writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
}
static int __init tcb_clksrc_init(void)
{
static char bootinfo[] __initdata
= KERN_DEBUG "%s: tc%d at %d.%03d MHz\n";
struct platform_device *pdev;
struct atmel_tc *tc;
struct clk *t0_clk;
u32 rate, divided_rate = 0;
int best_divisor_idx = -1;
int clk32k_divisor_idx = -1;
int i;
tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK, clksrc.name);
if (!tc) {
pr_debug("can't alloc TC for clocksource\n");
return -ENODEV;
}
tcaddr = tc->regs;
pdev = tc->pdev;
t0_clk = tc->clk[0];
clk_enable(t0_clk);
/* How fast will we be counting? Pick something over 5 MHz. */
rate = (u32) clk_get_rate(t0_clk);
for (i = 0; i < 5; i++) {
unsigned divisor = atmel_tc_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;
}
printk(bootinfo, clksrc.name, CONFIG_ATMEL_TCB_CLKSRC_BLOCK,
divided_rate / 1000000,
((divided_rate + 500000) % 1000000) / 1000);
if (tc->tcb_config && tc->tcb_config->counter_width == 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);
} else {
/* tclib will give us three clocks no matter what the
* underlying platform supports.
*/
clk_enable(tc->clk[1]);
/* setup both channel 0 & 1 */
tcb_setup_dual_chan(tc, best_divisor_idx);
}
/* and away we go! */
clocksource_register_hz(&clksrc, divided_rate);
/* channel 2: periodic and oneshot timer support */
setup_clkevents(tc, clk32k_divisor_idx);
return 0;
}
arch_initcall(tcb_clksrc_init);