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* [PATCH] ARM: smp_twd: Reconfigure clockevents after cpufreq change
@ 2011-06-01  9:15 Linus Walleij
  2011-06-14  5:50 ` Linus Walleij
  0 siblings, 1 reply; 11+ messages in thread
From: Linus Walleij @ 2011-06-01  9:15 UTC (permalink / raw)
  To: linux-arm-kernel

From: Colin Cross <ccross@android.com>

The localtimer's clock changes with the cpu clock. After a
cpufreq transition, update the clockevent's frequency and
reprogram the next clock event.

Adds a clock called "smp_twd" that is used to determine the
twd frequency, which can also be used at init time to
avoid calibrating the twd frequency.

Clock changes are based on Rob Herring's work.

Signed-off-by: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
[ifdef:ed CPUfreq stuff for non-cpufreq configs]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
I'm sending this as a pull request to Russells in this form,
this nasty cpufreq bug which is making the system timeline
jump back and forth on ux500 is *certainly* -rc material to me,
but I'm leaving it for Russell to decide.

Tested with and without CPUfreq support.
---
 arch/arm/kernel/smp_twd.c |   90 ++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 60636f4..5c8775d 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -10,13 +10,17 @@
  */
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/clk.h>
+#include <linux/cpufreq.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/smp.h>
 #include <linux/jiffies.h>
 #include <linux/clockchips.h>
 #include <linux/irq.h>
 #include <linux/io.h>
+#include <linux/percpu.h>
 
 #include <asm/smp_twd.h>
 #include <asm/hardware/gic.h>
@@ -24,7 +28,9 @@
 /* set up by the platform code */
 void __iomem *twd_base;
 
+static struct clk *twd_clk;
 static unsigned long twd_timer_rate;
+static DEFINE_PER_CPU(struct clock_event_device *, twd_ce);
 
 static void twd_set_mode(enum clock_event_mode mode,
 			struct clock_event_device *clk)
@@ -80,6 +86,52 @@ int twd_timer_ack(void)
 	return 0;
 }
 
+#ifdef CONFIG_CPU_FREQ
+
+/*
+ * Updates clockevent frequency when the cpu frequency changes.
+ * Called on the cpu that is changing frequency with interrupts disabled.
+ */
+static void twd_update_frequency(void *data)
+{
+	twd_timer_rate = clk_get_rate(twd_clk);
+
+	clockevents_update_freq(__get_cpu_var(twd_ce), twd_timer_rate);
+}
+
+static int twd_cpufreq_transition(struct notifier_block *nb,
+	unsigned long state, void *data)
+{
+	struct cpufreq_freqs *freqs = data;
+
+	/*
+	 * The twd clock events must be reprogrammed to account for the new
+	 * frequency.  The timer is local to a cpu, so cross-call to the
+	 * changing cpu.
+	 */
+	if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE)
+		smp_call_function_single(freqs->cpu, twd_update_frequency,
+			NULL, 1);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block twd_cpufreq_nb = {
+	.notifier_call = twd_cpufreq_transition,
+};
+
+static int twd_cpufreq_init(void)
+{
+	if (!IS_ERR_OR_NULL(twd_clk))
+		return cpufreq_register_notifier(&twd_cpufreq_nb,
+			CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+}
+core_initcall(twd_cpufreq_init);
+
+#endif
+
 static void __cpuinit twd_calibrate_rate(void)
 {
 	unsigned long count;
@@ -119,12 +171,39 @@ static void __cpuinit twd_calibrate_rate(void)
 	}
 }
 
+static struct clk *twd_get_clock(void)
+{
+	struct clk *clk;
+	int err;
+
+	clk = clk_get_sys("smp_twd", NULL);
+	if (IS_ERR(clk)) {
+		pr_err("smp_twd: clock not found: %d\n", (int)PTR_ERR(clk));
+		return clk;
+	}
+
+	err = clk_enable(clk);
+	if (err) {
+		pr_err("smp_twd: clock failed to enable: %d\n", err);
+		clk_put(clk);
+		return ERR_PTR(err);
+	}
+
+	return clk;
+}
+
 /*
  * Setup the local clock events for a CPU.
  */
 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 {
-	twd_calibrate_rate();
+	if (!twd_clk)
+		twd_clk = twd_get_clock();
+
+	if (!IS_ERR_OR_NULL(twd_clk))
+		twd_timer_rate = clk_get_rate(twd_clk);
+	else
+		twd_calibrate_rate();
 
 	clk->name = "local_timer";
 	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
@@ -132,13 +211,12 @@ void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 	clk->rating = 350;
 	clk->set_mode = twd_set_mode;
 	clk->set_next_event = twd_set_next_event;
-	clk->shift = 20;
-	clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
-	clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
-	clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 
 	/* Make sure our local interrupt controller has this enabled */
 	gic_enable_ppi(clk->irq);
 
-	clockevents_register_device(clk);
+	__get_cpu_var(twd_ce) = clk;
+
+	clockevents_config_and_register(clk, twd_timer_rate,
+					0xf, 0xffffffff);
 }
-- 
1.7.3.2

^ permalink raw reply related	[flat|nested] 11+ messages in thread
* [PATCH] ARM: smp_twd: Reconfigure clockevents after cpufreq change
@ 2011-05-16 23:21 Colin Cross
  2011-05-17 14:00 ` Santosh Shilimkar
  2011-05-19 17:32 ` Linus Walleij
  0 siblings, 2 replies; 11+ messages in thread
From: Colin Cross @ 2011-05-16 23:21 UTC (permalink / raw)
  To: linux-arm-kernel

The localtimer's clock changes with the cpu clock.  After a
cpufreq transition, update the clockevent's frequency and
reprogram the next clock event.

Adds a clock called "smp_twd" that is used to determine the
twd frequency, which can also be used at init time to
avoid calibrating the twd frequency.

Signed-off-by: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Rob Herring <robherring2@gmail.com>
---
 arch/arm/kernel/smp_twd.c |   69 +++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 66 insertions(+), 3 deletions(-)

This patch depends on Thomas Gleixner's patch to add clockevents_reconfigure
See: https://lkml.org/lkml/2011/5/13/122

This patch adds a clock that can be used to skip calibration as well
as update the frequency.  A later patch (or a later version of this patch)
will drop twd_calibrate_rate once all platforms provide the necessary
smp_twd clock.

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 60636f4..dbf58d4 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -10,21 +10,29 @@
  */
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/clk.h>
+#include <linux/cpufreq.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/smp.h>
 #include <linux/jiffies.h>
 #include <linux/clockchips.h>
 #include <linux/irq.h>
 #include <linux/io.h>
+#include <linux/percpu.h>
 
 #include <asm/smp_twd.h>
 #include <asm/hardware/gic.h>
 
+#define TWD_MIN_RANGE 4
+
 /* set up by the platform code */
 void __iomem *twd_base;
 
+static struct clk *twd_clk;
 static unsigned long twd_timer_rate;
+static DEFINE_PER_CPU(struct clock_event_device *, twd_ce);
 
 static void twd_set_mode(enum clock_event_mode mode,
 			struct clock_event_device *clk)
@@ -80,6 +88,49 @@ int twd_timer_ack(void)
 	return 0;
 }
 
+/*
+ * Updates clockevent frequency when the cpu frequency changes.
+ * Called on the cpu that is changing frequency with interrupts disabled.
+ */
+static void twd_update_frequency(void *data)
+{
+	twd_timer_rate = clk_get_rate(twd_clk);
+
+	clockevents_reconfigure(__get_cpu_var(twd_ce), twd_timer_rate,
+			TWD_MIN_RANGE);
+}
+
+static int twd_cpufreq_transition(struct notifier_block *nb,
+	unsigned long state, void *data)
+{
+	struct cpufreq_freqs *freqs = data;
+
+	/*
+	 * The twd clock events must be reprogrammed to account for the new
+	 * frequency.  The timer is local to a cpu, so cross-call to the
+	 * changing cpu.
+	 */
+	if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE)
+		smp_call_function_single(freqs->cpu, twd_update_frequency,
+			NULL, 1);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block twd_cpufreq_nb = {
+	.notifier_call = twd_cpufreq_transition,
+};
+
+static int twd_cpufreq_init(void)
+{
+	if (!IS_ERR_OR_NULL(twd_clk))
+		return cpufreq_register_notifier(&twd_cpufreq_nb,
+			CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+}
+core_initcall(twd_cpufreq_init);
+
 static void __cpuinit twd_calibrate_rate(void)
 {
 	unsigned long count;
@@ -124,7 +175,16 @@ static void __cpuinit twd_calibrate_rate(void)
  */
 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 {
-	twd_calibrate_rate();
+	if (twd_clk == NULL) {
+		twd_clk = clk_get_sys("smp_twd", NULL);
+		if (IS_ERR_OR_NULL(twd_clk))
+			pr_warn("%s: no clock found\n", __func__);
+	}
+
+	if (!IS_ERR_OR_NULL(twd_clk))
+		twd_timer_rate = clk_get_rate(twd_clk);
+	else
+		twd_calibrate_rate();
 
 	clk->name = "local_timer";
 	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
@@ -132,13 +192,16 @@ void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 	clk->rating = 350;
 	clk->set_mode = twd_set_mode;
 	clk->set_next_event = twd_set_next_event;
-	clk->shift = 20;
-	clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
+
+	clockevents_calc_mult_shift(clk, twd_timer_rate, TWD_MIN_RANGE);
+
 	clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
 	clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 
 	/* Make sure our local interrupt controller has this enabled */
 	gic_enable_ppi(clk->irq);
 
+	__get_cpu_var(twd_ce) = clk;
+
 	clockevents_register_device(clk);
 }
-- 
1.7.4.1

^ permalink raw reply related	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2011-06-14  6:14 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-06-01  9:15 [PATCH] ARM: smp_twd: Reconfigure clockevents after cpufreq change Linus Walleij
2011-06-14  5:50 ` Linus Walleij
2011-06-14  6:00   ` Colin Cross
2011-06-14  6:12     ` Santosh Shilimkar
2011-06-14  6:14       ` Linus Walleij
  -- strict thread matches above, loose matches on Subject: below --
2011-05-16 23:21 Colin Cross
2011-05-17 14:00 ` Santosh Shilimkar
2011-05-17 17:06   ` Colin Cross
2011-05-18 11:32     ` Santosh Shilimkar
2011-05-19 17:32 ` Linus Walleij
2011-05-19 23:26   ` Colin Cross

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