[PATCH 2/5] ARM: s3c64xx: Add generic high resolution time support using PWM timers.
Tomasz Figa
tomasz.figa at gmail.com
Sat Aug 27 20:45:06 EDT 2011
This patch adds a sys_timer implementing generic clock source and clock event
device on S3C64xx using PWM timers 3 and 4. It can be enabled by a Kconfig
option, based on which either the new sys_timer is used as s3c64xx_timer or
s3c64xx_timer is defined to s3c24xx_timer which is the old tick timer.
Signed-off-by: Tomasz Figa <tomasz.figa at gmail.com>
---
arch/arm/Kconfig | 1 -
arch/arm/mach-s3c64xx/Kconfig | 12 ++
arch/arm/mach-s3c64xx/Makefile | 3 +
arch/arm/mach-s3c64xx/time.c | 320 ++++++++++++++++++++++++++++++
arch/arm/plat-samsung/include/plat/cpu.h | 7 +
5 files changed, 342 insertions(+), 1 deletions(-)
create mode 100644 arch/arm/mach-s3c64xx/time.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9adc278..05941f6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -700,7 +700,6 @@ config ARCH_S3C64XX
select ARM_VIC
select HAVE_CLK
select NO_IOPORT
- select ARCH_USES_GETTIMEOFFSET
select ARCH_HAS_CPUFREQ
select ARCH_REQUIRE_GPIOLIB
select SAMSUNG_CLKSRC
diff --git a/arch/arm/mach-s3c64xx/Kconfig b/arch/arm/mach-s3c64xx/Kconfig
index e4177e2..2db76fd 100644
--- a/arch/arm/mach-s3c64xx/Kconfig
+++ b/arch/arm/mach-s3c64xx/Kconfig
@@ -25,6 +25,18 @@ config CPU_S3C6410
help
Enable S3C6410 CPU support
+config S3C64XX_GENERIC_CLOCKEVENTS
+ bool "Enable high resolution generic time support using PWM timers"
+ select GENERIC_CLOCKEVENTS
+ help
+ This option enables high resolution generic time support
+ on S3C6400/S3C6410 SoCs using PWM timers 3 and 4 instead
+ of standard periodic tick using PWM timer 4.
+
+config S3C64XX_ARCH_USES_GETTIMEOFFSET
+ def_bool y if !S3C64XX_GENERIC_CLOCKEVENTS
+ select ARCH_USES_GETTIMEOFFSET
+
config S3C64XX_DMA
bool "S3C64XX DMA"
select S3C_DMA
diff --git a/arch/arm/mach-s3c64xx/Makefile b/arch/arm/mach-s3c64xx/Makefile
index 4657363..a152002 100644
--- a/arch/arm/mach-s3c64xx/Makefile
+++ b/arch/arm/mach-s3c64xx/Makefile
@@ -15,6 +15,9 @@ obj-y += cpu.o
obj-y += clock.o
obj-y += gpiolib.o
+# Generic clockevents
+obj-$(CONFIG_S3C64XX_GENERIC_CLOCKEVENTS) += time.o
+
# Core support for S3C6400 system
obj-$(CONFIG_CPU_S3C6400) += s3c6400.o
diff --git a/arch/arm/mach-s3c64xx/time.c b/arch/arm/mach-s3c64xx/time.c
new file mode 100644
index 0000000..4fa57f0
--- /dev/null
+++ b/arch/arm/mach-s3c64xx/time.c
@@ -0,0 +1,320 @@
+/* linux/arch/arm/mach-s3c64xx/time.c
+ *
+ * Copyright (c) 2011 Tomasz Figa <tomasz.figa at gmail.com>
+ *
+ * based on linux/arch/arm/plat-samsung/s5p-time.c
+ *
+ * S3C64XX generic high resolution time support using PWM 3 and PWM 4 timers.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Notes:
+ * - Frequency divisors are currently hardcoded to make both timers operate
+ * at 1/6 the frequency of PCLK, so with the usual PCLK frequency of 66 MHz,
+ * the timers are clocked at 11 MHz giving us the operating range from
+ * 90 nsec to 386 sec.
+ * - PWM registers, especially TCON, are shared with PWM driver, but since
+ * all the clock event callbacks are run in atomic context synchronization
+ * is not needed.
+ */
+
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/err.h>
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/platform_device.h>
+
+#include <mach/map.h>
+#include <plat/regs-timer.h>
+#include <asm/mach/time.h>
+
+#define PWM_EVENT (3)
+#define PWM_SOURCE (4)
+
+#define ONESHOT (0)
+#define PERIODIC (1)
+
+#define TCNT_MAX (0xffffffff)
+
+static struct clk *timerclk;
+
+/*
+ * PWM timers setup code
+ */
+
+static inline void s3c64xx_pwm_stop(unsigned int pwm_id)
+{
+ unsigned long tcon = __raw_readl(S3C2410_TCON);
+
+ switch (pwm_id) {
+ case 3:
+ tcon &= ~S3C2410_TCON_T3START;
+ break;
+ case 4:
+ tcon &= ~S3C2410_TCON_T4START;
+ break;
+ }
+
+ __raw_writel(tcon, S3C2410_TCON);
+}
+
+static inline void s3c64xx_pwm_init(unsigned int pwm_id, unsigned long tcnt)
+{
+ unsigned long tcon = __raw_readl(S3C2410_TCON);
+
+ /* timers reload after counting zero, so reduce the count by 1 */
+ --tcnt;
+
+ /* stop the timer and ask it to load the new value */
+ switch (pwm_id) {
+ case 3:
+ tcon &= ~(0xf<<16);
+ tcon |= S3C2410_TCON_T3MANUALUPD;
+ break;
+ case 4:
+ tcon &= ~(7<<20);
+ tcon |= S3C2410_TCON_T4MANUALUPD;
+ break;
+ }
+
+ __raw_writel(tcnt, S3C2410_TCNTB(pwm_id));
+ __raw_writel(tcnt, S3C2410_TCMPB(pwm_id));
+ __raw_writel(tcon, S3C2410_TCON);
+}
+
+static inline void s3c64xx_pwm_start(unsigned int pwm_id, bool periodic)
+{
+ unsigned long tcon = __raw_readl(S3C2410_TCON);
+
+ switch (pwm_id) {
+ case 3:
+ tcon |= S3C2410_TCON_T3START;
+ tcon &= ~S3C2410_TCON_T3MANUALUPD;
+
+ if (periodic)
+ tcon |= S3C2410_TCON_T3RELOAD;
+ else
+ tcon &= ~S3C2410_TCON_T3RELOAD;
+ break;
+ case 4:
+ tcon |= S3C2410_TCON_T4START;
+ tcon &= ~S3C2410_TCON_T4MANUALUPD;
+
+ if (periodic)
+ tcon |= S3C2410_TCON_T4RELOAD;
+ else
+ tcon &= ~S3C2410_TCON_T4RELOAD;
+ break;
+ }
+
+ __raw_writel(tcon, S3C2410_TCON);
+}
+
+/*
+ * Clock event
+ */
+
+static struct clk *event_in;
+static struct clk *event_div;
+
+static unsigned long clock_count_per_tick;
+
+static int s3c64xx_clock_event_set_next_event(unsigned long cycles,
+ struct clock_event_device *evt)
+{
+ s3c64xx_pwm_init(PWM_EVENT, cycles);
+ s3c64xx_pwm_start(PWM_EVENT, ONESHOT);
+ return 0;
+}
+
+static void s3c64xx_clock_event_resume(void)
+{
+ unsigned long pclk;
+ struct clk *tscaler;
+
+ pclk = clk_get_rate(timerclk);
+ tscaler = clk_get_parent(event_div);
+ clk_set_rate(tscaler, pclk / 3);
+
+ clk_set_rate(event_div, pclk / 6);
+ clk_set_parent(event_in, event_div);
+
+ s3c64xx_pwm_init(PWM_EVENT, clock_count_per_tick);
+ s3c64xx_pwm_start(PWM_EVENT, PERIODIC);
+}
+
+static void s3c64xx_clock_event_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *evt)
+{
+ s3c64xx_pwm_stop(PWM_EVENT);
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ s3c64xx_pwm_init(PWM_EVENT, clock_count_per_tick);
+ s3c64xx_pwm_start(PWM_EVENT, PERIODIC);
+ break;
+ case CLOCK_EVT_MODE_ONESHOT:
+ break;
+ case CLOCK_EVT_MODE_UNUSED:
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ break;
+ case CLOCK_EVT_MODE_RESUME:
+ s3c64xx_clock_event_resume();
+ break;
+ }
+}
+
+static struct clock_event_device s3c64xx_clock_event_device = {
+ .name = "s3c64xx_clkevt",
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .rating = 200,
+ .shift = 32,
+ .set_next_event = s3c64xx_clock_event_set_next_event,
+ .set_mode = s3c64xx_clock_event_set_mode,
+};
+
+static irqreturn_t s3c64xx_clock_event_isr(int irq, void *dev_id)
+{
+ struct clock_event_device *evt = &s3c64xx_clock_event_device;
+
+ evt->event_handler(evt);
+
+ return IRQ_HANDLED;
+}
+
+static struct irqaction s3c64xx_clock_event_irq = {
+ .name = "s3c64xx_clkevt_irq",
+ .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
+ .handler = s3c64xx_clock_event_isr,
+};
+
+static void __init s3c64xx_clock_event_init(void)
+{
+ unsigned long clock_rate;
+
+ clock_rate = clk_get_rate(event_in);
+
+ clock_count_per_tick = clock_rate / HZ;
+
+ s3c64xx_clock_event_device.mult = div_sc(clock_rate,
+ NSEC_PER_SEC, s3c64xx_clock_event_device.shift);
+ s3c64xx_clock_event_device.max_delta_ns =
+ clockevent_delta2ns(-1, &s3c64xx_clock_event_device);
+ s3c64xx_clock_event_device.min_delta_ns =
+ clockevent_delta2ns(1, &s3c64xx_clock_event_device);
+
+ s3c64xx_clock_event_device.cpumask = cpumask_of(0);
+ clockevents_register_device(&s3c64xx_clock_event_device);
+
+ setup_irq(IRQ_TIMER3, &s3c64xx_clock_event_irq);
+}
+
+/*
+ * Clock source
+ */
+
+static struct clk *source_in;
+static struct clk *source_div;
+
+static cycle_t s3c64xx_clocksource_read(struct clocksource *cs)
+{
+ return (cycle_t) ~__raw_readl(S3C2410_TCNTO(PWM_SOURCE));
+}
+
+static void s3c64xx_clocksource_resume(struct clocksource *cs)
+{
+ unsigned long pclk;
+ struct clk *tscaler;
+
+ pclk = clk_get_rate(timerclk);
+ tscaler = clk_get_parent(source_div);
+ clk_set_rate(tscaler, pclk / 3);
+
+ clk_set_rate(source_div, pclk / 6);
+ clk_set_parent(source_in, source_div);
+
+ s3c64xx_pwm_init(PWM_SOURCE, TCNT_MAX);
+ s3c64xx_pwm_start(PWM_SOURCE, PERIODIC);
+}
+
+static struct clocksource pwm_clocksource = {
+ .name = "s3c64xx_clksrc",
+ .rating = 250,
+ .read = s3c64xx_clocksource_read,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .resume = s3c64xx_clocksource_resume,
+};
+
+static void __init s3c64xx_clocksource_init(void)
+{
+ unsigned long clock_rate;
+
+ clock_rate = clk_get_rate(source_in);
+
+ s3c64xx_pwm_init(PWM_SOURCE, TCNT_MAX);
+ s3c64xx_pwm_start(PWM_SOURCE, PERIODIC);
+
+ if (clocksource_register_hz(&pwm_clocksource, clock_rate))
+ panic("%s: can't register clocksource\n", pwm_clocksource.name);
+}
+
+static void __init s3c64xx_timer_init_common(void)
+{
+ struct platform_device tmpdev;
+ unsigned long pclk;
+ struct clk *tscaler;
+
+ tmpdev.dev.bus = &platform_bus_type;
+
+ timerclk = clk_get(NULL, "timers");
+ if (IS_ERR(timerclk))
+ panic("failed to get timers clock for system timer");
+
+ tmpdev.id = PWM_EVENT;
+ event_in = clk_get(&tmpdev.dev, "pwm-tin");
+ if (IS_ERR(event_in))
+ panic("failed to get pwm-event_in clock for system timer");
+
+ event_div = clk_get(&tmpdev.dev, "pwm-tdiv");
+ if (IS_ERR(event_div))
+ panic("failed to get pwm-event_div clock for system timer");
+
+ tmpdev.id = PWM_SOURCE;
+ source_in = clk_get(&tmpdev.dev, "pwm-tin");
+ if (IS_ERR(source_in))
+ panic("failed to get pwm-source_in clock for system timer");
+
+ source_div = clk_get(&tmpdev.dev, "pwm-tdiv");
+ if (IS_ERR(source_div))
+ panic("failed to get pwm-source_div clock for system timer");
+
+ pclk = clk_get_rate(timerclk);
+ tscaler = clk_get_parent(event_div);
+ clk_set_rate(tscaler, pclk / 3);
+
+ clk_set_rate(event_div, pclk / 6);
+ clk_set_parent(event_in, event_div);
+
+ clk_set_rate(source_div, pclk / 6);
+ clk_set_parent(source_in, source_div);
+
+ clk_enable(timerclk);
+ clk_enable(event_in);
+ clk_enable(source_in);
+}
+
+static void __init s3c64xx_timer_init(void)
+{
+ s3c64xx_timer_init_common();
+ s3c64xx_clock_event_init();
+ s3c64xx_clocksource_init();
+}
+
+struct sys_timer s3c64xx_timer = {
+ .init = s3c64xx_timer_init,
+};
diff --git a/arch/arm/plat-samsung/include/plat/cpu.h b/arch/arm/plat-samsung/include/plat/cpu.h
index c0a5741..e1fcad0 100644
--- a/arch/arm/plat-samsung/include/plat/cpu.h
+++ b/arch/arm/plat-samsung/include/plat/cpu.h
@@ -74,6 +74,13 @@ extern struct syscore_ops s3c2416_pm_syscore_ops;
extern struct syscore_ops s3c244x_pm_syscore_ops;
extern struct syscore_ops s3c64xx_irq_syscore_ops;
+/* timer for 64xx */
+#ifdef CONFIG_S3C64XX_GENERIC_CLOCKEVENTS
+extern struct sys_timer s3c64xx_timer;
+#else
+#define s3c64xx_timer s3c24xx_timer
+#endif
+
/* system device classes */
extern struct sysdev_class s3c2410_sysclass;
--
1.7.6.1
More information about the linux-arm-kernel
mailing list