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Message-ID: <20091108010043.11c8bdaa@mycelium.queued.net>
Date: Sun, 8 Nov 2009 01:00:43 -0500
From: Andres Salomon <dilinger@...labora.co.uk>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-geode@...ts.infradead.org,
cjb@...top.org, deepak@...top.org,
Jordan Crouse <jordan@...micpenguin.net>
Subject: [PATCH 2/6] CS5535: add a generic clock event MFGPT driver
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.
Signed-off-by: Andres Salomon <dilinger@...labora.co.uk>
---
drivers/Kconfig | 2 +
drivers/clocksource/Kconfig | 9 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/cs5535-clockevt.c | 196 +++++++++++++++++++++++++++++++++
4 files changed, 208 insertions(+), 0 deletions(-)
create mode 100644 drivers/clocksource/Kconfig
create mode 100644 drivers/clocksource/cs5535-clockevt.c
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 48bbdbe..b4bc5a4 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -98,6 +98,8 @@ source "drivers/edac/Kconfig"
source "drivers/rtc/Kconfig"
+source "drivers/clocksource/Kconfig"
+
source "drivers/dma/Kconfig"
source "drivers/dca/Kconfig"
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
new file mode 100644
index 0000000..08f726c
--- /dev/null
+++ b/drivers/clocksource/Kconfig
@@ -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.
+
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index eef216f..be61ece 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -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
diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
new file mode 100644
index 0000000..29e8621
--- /dev/null
+++ b/drivers/clocksource/cs5535-clockevt.c
@@ -0,0 +1,196 @@
+/*
+ * Clock event driver for the CS5535/CS5536
+ *
+ * Copyright (C) 2006, Advanced Micro Devices, Inc.
+ * Copyright (C) 2007 Andres Salomon <dilinger@...ian.org>
+ * Copyright (C) 2009 Andres Salomon <dilinger@...labora.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/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@...labora.co.uk>");
+MODULE_DESCRIPTION("CS5535/CS5536 MFGPT clock event driver");
+MODULE_LICENSE("GPL");
--
1.5.6.5
--
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