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cs5535: add a generic clock event MFGPT driver

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This is based on the old code in arch/x86/kernel/mfgpt_32.c, but is
modular and not Geode-specific.  There's no reason why the clock event
device needs to be registered so early at boot; the clockevent code is
perfectly capable of dynamic switching.

[akpm@linux-foundation.org: add linux/irq.h include]
Signed-off-by: Andres Salomon <dilinger@collabora.co.uk>
Cc: Jordan Crouse <jordan@cosmicpenguin.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Chris Ball <cjb@laptop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andres Salomon 2009-12-14 18:00:38 -08:00 committed by Linus Torvalds
parent 82dca611bb
commit c30d7d2b99
4 changed files with 209 additions and 0 deletions
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2
drivers/Kconfig
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@ -96,6 +96,8 @@ source "drivers/edac/Kconfig"
source "drivers/rtc/Kconfig"
source "drivers/clocksource/Kconfig"
source "drivers/dma/Kconfig"
source "drivers/dca/Kconfig"

9
drivers/clocksource/Kconfig Normal file
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@ -0,0 +1,9 @@
config CS5535_CLOCK_EVENT_SRC
tristate "CS5535/CS5536 high-res timer (MFGPT) events"
depends on GENERIC_TIME && GENERIC_CLOCKEVENTS && CS5535_MFGPT
help
This driver provides a clock event source based on the MFGPT
timer(s) in the CS5535 and CS5536 companion chips.
MFGPTs have a better resolution and max interval than the
generic PIT, and are suitable for use as high-res timers.

1
drivers/clocksource/Makefile
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@ -2,6 +2,7 @@ obj-$(CONFIG_ATMEL_TCB_CLKSRC) += tcb_clksrc.o
obj-$(CONFIG_X86_CYCLONE_TIMER) += cyclone.o
obj-$(CONFIG_X86_PM_TIMER) += acpi_pm.o
obj-$(CONFIG_SCx200HR_TIMER) += scx200_hrt.o
obj-$(CONFIG_CS5535_CLOCK_EVENT_SRC) += cs5535-clockevt.o
obj-$(CONFIG_SH_TIMER_CMT) += sh_cmt.o
obj-$(CONFIG_SH_TIMER_MTU2) += sh_mtu2.o
obj-$(CONFIG_SH_TIMER_TMU) += sh_tmu.o

197
drivers/clocksource/cs5535-clockevt.c Normal file
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@ -0,0 +1,197 @@
/*
* Clock event driver for the CS5535/CS5536
*
* Copyright (C) 2006, Advanced Micro Devices, Inc.
* Copyright (C) 2007 Andres Salomon <dilinger@debian.org>
* Copyright (C) 2009 Andres Salomon <dilinger@collabora.co.uk>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public License
* as published by the Free Software Foundation.
*
* The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
*/
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/cs5535.h>
#include <linux/clockchips.h>
#define DRV_NAME "cs5535-clockevt"
static int timer_irq = CONFIG_CS5535_MFGPT_DEFAULT_IRQ;
module_param_named(irq, timer_irq, int, 0644);
MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks.");
/*
* We are using the 32.768kHz input clock - it's the only one that has the
* ranges we find desirable. The following table lists the suitable
* divisors and the associated Hz, minimum interval and the maximum interval:
*
* Divisor Hz Min Delta (s) Max Delta (s)
* 1 32768 .00048828125 2.000
* 2 16384 .0009765625 4.000
* 4 8192 .001953125 8.000
* 8 4096 .00390625 16.000
* 16 2048 .0078125 32.000
* 32 1024 .015625 64.000
* 64 512 .03125 128.000
* 128 256 .0625 256.000
* 256 128 .125 512.000
*/
static unsigned int cs5535_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
static struct cs5535_mfgpt_timer *cs5535_event_clock;
/* Selected from the table above */
#define MFGPT_DIVISOR 16
#define MFGPT_SCALE 4 /* divisor = 2^(scale) */
#define MFGPT_HZ (32768 / MFGPT_DIVISOR)
#define MFGPT_PERIODIC (MFGPT_HZ / HZ)
/*
* 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 than 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.
*/
static void disable_timer(struct cs5535_mfgpt_timer *timer)
{
/* avoid races by clearing CMP1 and CMP2 unconditionally */
cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
(uint16_t) ~MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP1 |
MFGPT_SETUP_CMP2);
}
static void start_timer(struct cs5535_mfgpt_timer *timer, uint16_t delta)
{
cs5535_mfgpt_write(timer, MFGPT_REG_CMP2, delta);
cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0);
cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
}
static void mfgpt_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
disable_timer(cs5535_event_clock);
if (mode == CLOCK_EVT_MODE_PERIODIC)
start_timer(cs5535_event_clock, MFGPT_PERIODIC);
cs5535_tick_mode = mode;
}
static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt)
{
start_timer(cs5535_event_clock, delta);
return 0;
}
static struct clock_event_device cs5535_clockevent = {
.name = DRV_NAME,
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_mode = mfgpt_set_mode,
.set_next_event = mfgpt_next_event,
.rating = 250,
.cpumask = cpu_all_mask,
.shift = 32
};
static irqreturn_t mfgpt_tick(int irq, void *dev_id)
{
uint16_t val = cs5535_mfgpt_read(cs5535_event_clock, MFGPT_REG_SETUP);
/* See if the interrupt was for us */
if (!(val & (MFGPT_SETUP_SETUP | MFGPT_SETUP_CMP2 | MFGPT_SETUP_CMP1)))
return IRQ_NONE;
/* Turn off the clock (and clear the event) */
disable_timer(cs5535_event_clock);
if (cs5535_tick_mode == CLOCK_EVT_MODE_SHUTDOWN)
return IRQ_HANDLED;
/* Clear the counter */
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_COUNTER, 0);
/* Restart the clock in periodic mode */
if (cs5535_tick_mode == CLOCK_EVT_MODE_PERIODIC)
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP,
MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
cs5535_clockevent.event_handler(&cs5535_clockevent);
return IRQ_HANDLED;
}
static struct irqaction mfgptirq = {
.handler = mfgpt_tick,
.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER,
.name = DRV_NAME,
};
static int __init cs5535_mfgpt_init(void)
{
struct cs5535_mfgpt_timer *timer;
int ret;
uint16_t val;
timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
if (!timer) {
printk(KERN_ERR DRV_NAME ": Could not allocate MFPGT timer\n");
return -ENODEV;
}
cs5535_event_clock = timer;
/* Set up the IRQ on the MFGPT side */
if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) {
printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n",
timer_irq);
return -EIO;
}
/* And register it with the kernel */
ret = setup_irq(timer_irq, &mfgptirq);
if (ret) {
printk(KERN_ERR DRV_NAME ": Unable to set up the interrupt.\n");
goto err;
}
/* Set the clock scale and enable the event mode for CMP2 */
val = MFGPT_SCALE | (3 << 8);
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, val);
/* Set up the clock event */
cs5535_clockevent.mult = div_sc(MFGPT_HZ, NSEC_PER_SEC,
cs5535_clockevent.shift);
cs5535_clockevent.min_delta_ns = clockevent_delta2ns(0xF,
&cs5535_clockevent);
cs5535_clockevent.max_delta_ns = clockevent_delta2ns(0xFFFE,
&cs5535_clockevent);
printk(KERN_INFO DRV_NAME
": Registering MFGPT timer as a clock event, using IRQ %d\n",
timer_irq);
clockevents_register_device(&cs5535_clockevent);
return 0;
err:
cs5535_mfgpt_release_irq(cs5535_event_clock, MFGPT_CMP2, &timer_irq);
printk(KERN_ERR DRV_NAME ": Unable to set up the MFGPT clock source\n");
return -EIO;
}
module_init(cs5535_mfgpt_init);
MODULE_AUTHOR("Andres Salomon <dilinger@collabora.co.uk>");
MODULE_DESCRIPTION("CS5535/CS5536 MFGPT clock event driver");
MODULE_LICENSE("GPL");