Add support for an MFGPT clock event device; this allows us to use MFGPTs
as the basis for high-resolution timers.
Signed-off-by: Jordan Crouse <[email protected]>
Signed-off-by: Andres Salomon <[email protected]>
---
arch/i386/Kconfig | 10 +++
arch/i386/kernel/mfgpt.c | 160 +++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 169 insertions(+), 1 deletions(-)
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index d2f6a24..7be62ca 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -1190,6 +1190,16 @@ config SCx200HR_TIMER
processor goes idle (as is done by the scheduler). The
other workaround is idle=poll boot option.
+config GEODE_MFGPT_TIMER
+ bool "Geode Multi-Function General Purpose Timer (MFGPT) events"
+ depends on MGEODE_LX && GENERIC_TIME && GENERIC_CLOCKEVENTS
+ default y
+ help
+ This driver provides a clock event source based on the MFGPT
+ timer(s) in the CS5535 and CS5536 companion chip for the geode.
+ MFGPTs have a better resolution and max interval than the
+ generic PIT, and are suitable for use as high-res timers.
+
config K8_NB
def_bool y
depends on AGP_AMD64
diff --git a/arch/i386/kernel/mfgpt.c b/arch/i386/kernel/mfgpt.c
index b13c34f..5fadecf 100644
--- a/arch/i386/kernel/mfgpt.c
+++ b/arch/i386/kernel/mfgpt.c
@@ -48,6 +48,12 @@ static struct mfgpt_timer_t {
#define MFGPT_HZ (32000 / MFGPT_DIVISOR)
#define MFGPT_PERIODIC (MFGPT_HZ / HZ)
+#ifdef CONFIG_GEODE_MFGPT_TIMER
+static int __init mfgpt_timer_setup(void);
+#else
+#define mfgpt_timer_setup() (0)
+#endif
+
/* Allow for disabling of MFGPTs */
static int disable = 0;
static int __init mfgpt_disable(char *s)
@@ -82,6 +88,9 @@ int __init geode_mfgpt_detect(void)
}
}
+ /* set up clock event device, if desired */
+ i = mfgpt_timer_setup();
+
return count;
}
@@ -99,7 +108,7 @@ int geode_mfgpt_toggle_event(int timer, int cmp, int event, int enable)
*/
switch (event) {
case MFGPT_EVENT_RESET:
- /*
+ /*
* XXX: According to the docs, we cannot reset timers above
* 6; that is, resets for 7 and 8 will be ignored. Is this
* a problem? -dilinger
@@ -198,3 +207,152 @@ int geode_mfgpt_alloc_timer(int timer, int domain, struct module *owner)
return -1;
}
EXPORT_SYMBOL(geode_mfgpt_alloc_timer);
+
+#ifdef CONFIG_GEODE_MFGPT_TIMER
+
+/*
+ * The MFPGT timers on the CS5536 provide us with suitable timers to use
+ * as clock event sources - not as good as a HPET or APIC, but certainly
+ * better then the PIT. This isn't a general purpose MFGPT driver, but
+ * a simplified one designed specifically to act as a clock event source.
+ * For full details about the MFGPT, please consult the CS5536 data sheet.
+ */
+
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+
+static unsigned int mfgpt_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
+static u16 mfgpt_event_clock;
+
+static int irq = 7;
+static int __init mfgpt_setup(char *str)
+{
+ get_option(&str, &irq);
+ return 1;
+}
+__setup("mfgpt_irq=", mfgpt_setup);
+
+static inline void mfgpt_disable_timer(u16 clock)
+{
+ u16 val = geode_mfgpt_read(clock, MFGPT_REG_SETUP);
+ geode_mfgpt_write(clock, MFGPT_REG_SETUP, val & ~MFGPT_SETUP_CNTEN);
+}
+
+static int mfgpt_next_event(unsigned long, struct clock_event_device *);
+static void mfgpt_set_mode(enum clock_event_mode, struct clock_event_device *);
+
+static struct clock_event_device mfgpt_clockevent = {
+ .name = "mfgpt-timer",
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .set_mode = mfgpt_set_mode,
+ .set_next_event = mfgpt_next_event,
+ .rating = 250,
+ .cpumask = CPU_MASK_ALL,
+ .shift = 32
+};
+
+static inline void mfgpt_start_timer(u16 clock, u16 delta)
+{
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_CMP2, (u16) delta);
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_COUNTER, 0);
+
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP,
+ MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
+}
+
+static void mfgpt_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *evt)
+{
+ mfgpt_disable_timer(mfgpt_event_clock);
+
+ if (mode == CLOCK_EVT_MODE_PERIODIC)
+ mfgpt_start_timer(mfgpt_event_clock, MFGPT_PERIODIC);
+
+ mfgpt_tick_mode = mode;
+}
+
+static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt)
+{
+ mfgpt_start_timer(mfgpt_event_clock, delta);
+ return 0;
+}
+
+/* Assume (foolishly?), that this interrupt was due to our tick */
+
+static irqreturn_t mfgpt_tick(int irq, void *dev_id)
+{
+ if (mfgpt_tick_mode == CLOCK_EVT_MODE_SHUTDOWN)
+ return IRQ_HANDLED;
+
+ /* Turn off the clock */
+ mfgpt_disable_timer(mfgpt_event_clock);
+
+ /* Clear the counter */
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_COUNTER, 0);
+
+ /* Restart the clock in periodic mode */
+
+ if (mfgpt_tick_mode == CLOCK_EVT_MODE_PERIODIC) {
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP,
+ MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
+ }
+
+ mfgpt_clockevent.event_handler(&mfgpt_clockevent);
+ return IRQ_HANDLED;
+}
+
+static struct irqaction mfgptirq = {
+ .handler = mfgpt_tick,
+ .flags = IRQF_DISABLED | IRQF_NOBALANCING,
+ .mask = CPU_MASK_NONE,
+ .name = "mfgpt-timer"
+};
+
+static int __init mfgpt_timer_setup(void)
+{
+ int timer, ret;
+ u16 val;
+
+ timer = geode_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING, THIS_MODULE);
+ if (timer < 0) {
+ printk(KERN_ERR "mfgpt-timer: Could not allocate a MFPGT timer\n");
+ return -ENODEV;
+ }
+
+ mfgpt_event_clock = timer;
+ /* Set the clock scale and enable the event mode for CMP2 */
+ val = MFGPT_SCALE | (3 << 8);
+
+ geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP, val);
+
+ /* Set up the IRQ on the MFGPT side */
+ if (geode_mfgpt_setup_irq(mfgpt_event_clock, MFGPT_CMP2, irq)) {
+ printk(KERN_ERR "mfgpt-timer: Could not set up IRQ %d\n", irq);
+ return -EIO;
+ }
+
+ /* And register it with the kernel */
+ ret = setup_irq(irq, &mfgptirq);
+
+ if (ret) {
+ printk(KERN_ERR "mfgpt-timer: Unable to set up the interrupt.\n");
+ goto err;
+ }
+
+ /* Set up the clock event */
+ mfgpt_clockevent.mult = div_sc(MFGPT_HZ, NSEC_PER_SEC, 32);
+ mfgpt_clockevent.min_delta_ns = clockevent_delta2ns(0xF, &mfgpt_clockevent);
+ mfgpt_clockevent.max_delta_ns = clockevent_delta2ns(0xFFFE, &mfgpt_clockevent);
+
+ printk("mfgpt-timer: registering the MFGT timer as a clock event.\n");
+ clockevents_register_device(&mfgpt_clockevent);
+
+ return 0;
+
+err:
+ geode_mfgpt_release_irq(mfgpt_event_clock, MFGPT_CMP2, irq);
+ printk(KERN_ERR "mfgpt-timer: Unable to set up the MFGPT clock source\n");
+ return -EIO;
+}
+
+#endif
--
1.5.2.2
-
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