linux/arch/mips/loongson64/loongson-3/hpet.c
Huacai Chen 3ef0665398 MIPS: hpet: Increase HPET_MIN_PROG_DELTA and decrease HPET_MIN_CYCLES
At first, we prefer to use mips clockevent device, so we decrease the
rating of hpet clockevent device.

For hpet, if HPET_MIN_PROG_DELTA (minimum delta of hpet programming) is
too small and HPET_MIN_CYCLES (threshold of -ETIME checking) is too
large, then hpet_next_event() can easily return -ETIME. After commit
c6eb3f70d4 ("hrtimer: Get rid of hrtimer softirq") this will cause
a RCU stall.

So, HPET_MIN_PROG_DELTA must be sufficient that we don't re-trip the
-ETIME check -- if we do, we will return -ETIME, forward the next event
time, try to set it, return -ETIME again, and basically lock the system
up. Meanwhile, HPET_MIN_CYCLES doesn't need to be too large, 16 cycles
is enough.

This solution is similar to commit f9eccf2461 ("clocksource/drivers
/vt8500: Increase the minimum delta").

By the way, this patch ensures hpet count/compare to be 32-bit long.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J . Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13819/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2016-07-24 12:01:00 +02:00

287 lines
6.2 KiB
C

#include <linux/init.h>
#include <linux/pci.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <asm/hpet.h>
#include <asm/time.h>
#define SMBUS_CFG_BASE (loongson_sysconf.ht_control_base + 0x0300a000)
#define SMBUS_PCI_REG40 0x40
#define SMBUS_PCI_REG64 0x64
#define SMBUS_PCI_REGB4 0xb4
#define HPET_MIN_CYCLES 16
#define HPET_MIN_PROG_DELTA (HPET_MIN_CYCLES * 12)
static DEFINE_SPINLOCK(hpet_lock);
DEFINE_PER_CPU(struct clock_event_device, hpet_clockevent_device);
static unsigned int smbus_read(int offset)
{
return *(volatile unsigned int *)(SMBUS_CFG_BASE + offset);
}
static void smbus_write(int offset, int data)
{
*(volatile unsigned int *)(SMBUS_CFG_BASE + offset) = data;
}
static void smbus_enable(int offset, int bit)
{
unsigned int cfg = smbus_read(offset);
cfg |= bit;
smbus_write(offset, cfg);
}
static int hpet_read(int offset)
{
return *(volatile unsigned int *)(HPET_MMIO_ADDR + offset);
}
static void hpet_write(int offset, int data)
{
*(volatile unsigned int *)(HPET_MMIO_ADDR + offset) = data;
}
static void hpet_start_counter(void)
{
unsigned int cfg = hpet_read(HPET_CFG);
cfg |= HPET_CFG_ENABLE;
hpet_write(HPET_CFG, cfg);
}
static void hpet_stop_counter(void)
{
unsigned int cfg = hpet_read(HPET_CFG);
cfg &= ~HPET_CFG_ENABLE;
hpet_write(HPET_CFG, cfg);
}
static void hpet_reset_counter(void)
{
hpet_write(HPET_COUNTER, 0);
hpet_write(HPET_COUNTER + 4, 0);
}
static void hpet_restart_counter(void)
{
hpet_stop_counter();
hpet_reset_counter();
hpet_start_counter();
}
static void hpet_enable_legacy_int(void)
{
/* Do nothing on Loongson-3 */
}
static int hpet_set_state_periodic(struct clock_event_device *evt)
{
int cfg;
spin_lock(&hpet_lock);
pr_info("set clock event to periodic mode!\n");
/* stop counter */
hpet_stop_counter();
/* enables the timer0 to generate a periodic interrupt */
cfg = hpet_read(HPET_T0_CFG);
cfg &= ~HPET_TN_LEVEL;
cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
HPET_TN_32BIT;
hpet_write(HPET_T0_CFG, cfg);
/* set the comparator */
hpet_write(HPET_T0_CMP, HPET_COMPARE_VAL);
udelay(1);
hpet_write(HPET_T0_CMP, HPET_COMPARE_VAL);
/* start counter */
hpet_start_counter();
spin_unlock(&hpet_lock);
return 0;
}
static int hpet_set_state_shutdown(struct clock_event_device *evt)
{
int cfg;
spin_lock(&hpet_lock);
cfg = hpet_read(HPET_T0_CFG);
cfg &= ~HPET_TN_ENABLE;
hpet_write(HPET_T0_CFG, cfg);
spin_unlock(&hpet_lock);
return 0;
}
static int hpet_set_state_oneshot(struct clock_event_device *evt)
{
int cfg;
spin_lock(&hpet_lock);
pr_info("set clock event to one shot mode!\n");
cfg = hpet_read(HPET_T0_CFG);
/*
* set timer0 type
* 1 : periodic interrupt
* 0 : non-periodic(oneshot) interrupt
*/
cfg &= ~HPET_TN_PERIODIC;
cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
hpet_write(HPET_T0_CFG, cfg);
spin_unlock(&hpet_lock);
return 0;
}
static int hpet_tick_resume(struct clock_event_device *evt)
{
spin_lock(&hpet_lock);
hpet_enable_legacy_int();
spin_unlock(&hpet_lock);
return 0;
}
static int hpet_next_event(unsigned long delta,
struct clock_event_device *evt)
{
u32 cnt;
s32 res;
cnt = hpet_read(HPET_COUNTER);
cnt += (u32) delta;
hpet_write(HPET_T0_CMP, cnt);
res = (s32)(cnt - hpet_read(HPET_COUNTER));
return res < HPET_MIN_CYCLES ? -ETIME : 0;
}
static irqreturn_t hpet_irq_handler(int irq, void *data)
{
int is_irq;
struct clock_event_device *cd;
unsigned int cpu = smp_processor_id();
is_irq = hpet_read(HPET_STATUS);
if (is_irq & HPET_T0_IRS) {
/* clear the TIMER0 irq status register */
hpet_write(HPET_STATUS, HPET_T0_IRS);
cd = &per_cpu(hpet_clockevent_device, cpu);
cd->event_handler(cd);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
static struct irqaction hpet_irq = {
.handler = hpet_irq_handler,
.flags = IRQF_NOBALANCING | IRQF_TIMER,
.name = "hpet",
};
/*
* hpet address assignation and irq setting should be done in bios.
* but pmon don't do this, we just setup here directly.
* The operation under is normal. unfortunately, hpet_setup process
* is before pci initialize.
*
* {
* struct pci_dev *pdev;
*
* pdev = pci_get_device(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS, NULL);
* pci_write_config_word(pdev, SMBUS_PCI_REGB4, HPET_ADDR);
*
* ...
* }
*/
static void hpet_setup(void)
{
/* set hpet base address */
smbus_write(SMBUS_PCI_REGB4, HPET_ADDR);
/* enable decoding of access to HPET MMIO*/
smbus_enable(SMBUS_PCI_REG40, (1 << 28));
/* HPET irq enable */
smbus_enable(SMBUS_PCI_REG64, (1 << 10));
hpet_enable_legacy_int();
}
void __init setup_hpet_timer(void)
{
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
hpet_setup();
cd = &per_cpu(hpet_clockevent_device, cpu);
cd->name = "hpet";
cd->rating = 100;
cd->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
cd->set_state_shutdown = hpet_set_state_shutdown;
cd->set_state_periodic = hpet_set_state_periodic;
cd->set_state_oneshot = hpet_set_state_oneshot;
cd->tick_resume = hpet_tick_resume;
cd->set_next_event = hpet_next_event;
cd->irq = HPET_T0_IRQ;
cd->cpumask = cpumask_of(cpu);
clockevent_set_clock(cd, HPET_FREQ);
cd->max_delta_ns = clockevent_delta2ns(0x7fffffff, cd);
cd->min_delta_ns = clockevent_delta2ns(HPET_MIN_PROG_DELTA, cd);
clockevents_register_device(cd);
setup_irq(HPET_T0_IRQ, &hpet_irq);
pr_info("hpet clock event device register\n");
}
static cycle_t hpet_read_counter(struct clocksource *cs)
{
return (cycle_t)hpet_read(HPET_COUNTER);
}
static void hpet_suspend(struct clocksource *cs)
{
}
static void hpet_resume(struct clocksource *cs)
{
hpet_setup();
hpet_restart_counter();
}
static struct clocksource csrc_hpet = {
.name = "hpet",
/* mips clocksource rating is less than 300, so hpet is better. */
.rating = 300,
.read = hpet_read_counter,
.mask = CLOCKSOURCE_MASK(32),
/* oneshot mode work normal with this flag */
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.suspend = hpet_suspend,
.resume = hpet_resume,
.mult = 0,
.shift = 10,
};
int __init init_hpet_clocksource(void)
{
csrc_hpet.mult = clocksource_hz2mult(HPET_FREQ, csrc_hpet.shift);
return clocksource_register_hz(&csrc_hpet, HPET_FREQ);
}
arch_initcall(init_hpet_clocksource);