Re: OMAP1 realtime patch

[Dirk Behme <dirk.behme@googlemail.com>]

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Kevin Hilman wrote:
> On Sun, 2007-02-11 at 18:01 +0100, Dirk Behme wrote:
> 
>>Dirk Behme wrote:
>>
>>>Kevin Hilman wrote:
>>>
>>>
>>>>Here is a patch which leaves out the raw_spinlock conversions.  It goes
>>>>on the OMAP git tree on top of -rt5 (ignoring conflicts.)  I've left out
>>>>all the raw_spinlock conversions.  This has been tested on an
>>>>OMAP1623/H2 platform.
>>>
>>>Update of Kevins update. Tested on OSK.
>>>
>>>Changes:
>>>
>>>- Remove kernel/printk.c "+    zap_rt_locks();". It's already in -rt5.
>>>
>>>- Re-add HRTIMER conversion to ads7846.c
>>>
>>>With this patch I get Oops below after playing mp3 via NFS. Add 
>>>raw_spinlock_t to sound/arm/omap/omap-alsa-dma.c like in my original 
>>>patch doesn't seem to help.
>>
>>Re-adding raw_spinlock_t to omap-alsa.h helps against this Oops.
> 
> 
> My guess the oops you sent is that you saw this crash when doing a
> Ctrl-C or otherwise stopping the playback, correct?

Nearly ;)

Even without Ctrl-C this Oops happened. Simply waiting for 
mp3 to finish and coming back to prompt triggered it.

Your patch fixes this.

> This oops is triggered by the same thread trying to take the same
> spinlock (now an rt_mutex under PREEMPT_RT.)  The following patch
> fixes the nested spinlocks,  and removes the raw_spinlock.  It applies
> on top of your latest patch.

Update to patch-2.6.20-rt5-omap3 in attachment.

Changes:

- Add Kevins fix for nested omap-alsa.c spinlocks and remove 
raw_spinlock workaround.

Thanks!

> On my OSK, I do notice however that using -rt (with and without this
> fix) mp3 playback has some audible noise under PREEMPT_RT.  Do you hear
> this too?

 > Another data point...  I only hear the noise when using 
mpg123 to play
 > an .mp3 file.  If I use aplay to play a .wav file, I'm 
not hearing any
 > noise.  I can even ping flood the target and audio plays 
without
 > problems.

I use madplay

MPEG Audio Decoder 0.15.2 (beta) - Copyright (C) 2000-2004 
Robert Leslie et al.

to play mp3. I explicitly checked it again and don't think 
there is any noise. Maybe a mpg123 related issue?

Far from it, I have the feeling that mp3 playback improves 
with -rt. In the past I had some random noise with my mp3 
test song (nobody else seemed to have ;) ). With -rt I have 
the impression that it's better.

Dirk

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Index: linux-osk/arch/arm/mach-omap1/time.c
===================================================================
--- linux-osk.orig/arch/arm/mach-omap1/time.c
+++ linux-osk/arch/arm/mach-omap1/time.c
@@ -42,6 +42,7 @@
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/clocksource.h>
+#include <linux/clockchips.h>
 
 #include <asm/system.h>
 #include <asm/hardware.h>
@@ -102,15 +103,33 @@ static inline unsigned long omap_mpu_tim
 	return timer->read_tim;
 }
 
-static inline void omap_mpu_timer_start(int nr, unsigned long load_val)
+static inline void omap_mpu_set_autoreset(int nr)
 {
 	volatile omap_mpu_timer_regs_t* timer = omap_mpu_timer_base(nr);
 
+	timer->cntl = timer->cntl | MPU_TIMER_AR;
+}
+
+static inline void omap_mpu_remove_autoreset(int nr)
+{
+	volatile omap_mpu_timer_regs_t* timer = omap_mpu_timer_base(nr);
+
+	timer->cntl = timer->cntl & ~MPU_TIMER_AR;
+}
+
+static inline void omap_mpu_timer_start(int nr, unsigned long load_val,
+					int autoreset)
+{
+	volatile omap_mpu_timer_regs_t* timer = omap_mpu_timer_base(nr);
+	unsigned int timerflags = (MPU_TIMER_CLOCK_ENABLE | MPU_TIMER_ST);
+
+	if (autoreset) timerflags |= MPU_TIMER_AR;
+
 	timer->cntl = MPU_TIMER_CLOCK_ENABLE;
 	udelay(1);
 	timer->load_tim = load_val;
         udelay(1);
-	timer->cntl = (MPU_TIMER_CLOCK_ENABLE | MPU_TIMER_AR | MPU_TIMER_ST);
+	timer->cntl = timerflags;
 }
 
 /*
@@ -118,12 +137,42 @@ static inline void omap_mpu_timer_start(
  * MPU timer 1 ... count down to zero, interrupt, reload
  * ---------------------------------------------------------------------------
  */
+static int omap_mpu_set_next_event(unsigned long cycles,
+				    struct clock_event_device *evt)
+{
+	omap_mpu_timer_start(0, cycles, 0);
+	return 0;
+}
+
+static void omap_mpu_set_mode(enum clock_event_mode mode,
+			      struct clock_event_device *evt)
+{
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		omap_mpu_set_autoreset(0);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		omap_mpu_remove_autoreset(0);
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		break;
+	}
+}
+
+static struct clock_event_device clockevent_mpu_timer1 = {
+	.name		= "mpu_timer1",
+	.features	= CLOCK_EVT_FEAT_PERIODIC, CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 32,
+	.set_next_event	= omap_mpu_set_next_event,
+	.set_mode	= omap_mpu_set_mode,
+};
+
 static irqreturn_t omap_mpu_timer1_interrupt(int irq, void *dev_id)
 {
-	write_seqlock(&xtime_lock);
-	/* NOTE:  no lost-tick detection/handling! */
-	timer_tick();
-	write_sequnlock(&xtime_lock);
+	struct clock_event_device *evt = &clockevent_mpu_timer1;
+
+	evt->event_handler(evt);
 
 	return IRQ_HANDLED;
 }
@@ -139,7 +188,17 @@ static __init void omap_init_mpu_timer(u
 	set_cyc2ns_scale(rate / 1000);
 
 	setup_irq(INT_TIMER1, &omap_mpu_timer1_irq);
-	omap_mpu_timer_start(0, (rate / HZ) - 1);
+	omap_mpu_timer_start(0, (rate / HZ) - 1, 1);
+
+	clockevent_mpu_timer1.mult = div_sc(rate, NSEC_PER_SEC,
+					    clockevent_mpu_timer1.shift);
+	clockevent_mpu_timer1.max_delta_ns =
+		clockevent_delta2ns(-1, &clockevent_mpu_timer1);
+	clockevent_mpu_timer1.min_delta_ns =
+		clockevent_delta2ns(1, &clockevent_mpu_timer1);
+
+	clockevent_mpu_timer1.cpumask = cpumask_of_cpu(0);
+	clockevents_register_device(&clockevent_mpu_timer1);
 }
 
 /*
@@ -173,7 +232,7 @@ static struct clocksource clocksource_mp
 	.read		= mpu_read,
 	.mask		= CLOCKSOURCE_MASK(32),
 	.shift		= 24,
-	.is_continuous	= 1,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
 static void __init omap_init_clocksource(unsigned long rate)
@@ -185,7 +244,7 @@ static void __init omap_init_clocksource
 		= clocksource_khz2mult(rate/1000, clocksource_mpu.shift);
 
 	setup_irq(INT_TIMER2, &omap_mpu_timer2_irq);
-	omap_mpu_timer_start(1, ~0);
+	omap_mpu_timer_start(1, ~0, 1);
 
 	if (clocksource_register(&clocksource_mpu))
 		printk(err, clocksource_mpu.name);
Index: linux-osk/arch/arm/plat-omap/timer32k.c
===================================================================
--- linux-osk.orig/arch/arm/plat-omap/timer32k.c
+++ linux-osk/arch/arm/plat-omap/timer32k.c
@@ -43,6 +43,7 @@
 #include <linux/err.h>
 #include <linux/clk.h>
 #include <linux/clocksource.h>
+#include <linux/clockchips.h>
 
 #include <asm/system.h>
 #include <asm/hardware.h>
@@ -210,23 +211,10 @@ unsigned long long sched_clock(void)
  */
 static inline irqreturn_t _omap_32k_timer_interrupt(int irq, void *dev_id)
 {
-	unsigned long now;
-
+	struct clock_event_device *evt = &clockevent_32k_timer;
 	omap_32k_timer_ack_irq();
-	now = omap_32k_sync_timer_read();
 
-	while ((signed long)(now - omap_32k_last_tick)
-						>= OMAP_32K_TICKS_PER_HZ) {
-		omap_32k_last_tick += OMAP_32K_TICKS_PER_HZ;
-		timer_tick();
-	}
-
-	/* Restart timer so we don't drift off due to modulo or dynamic tick.
-	 * By default we program the next timer to be continuous to avoid
-	 * latencies during high system load. During dynamic tick operation the
-	 * continuous timer can be overridden from pm_idle to be longer.
-	 */
-	omap_32k_timer_start(omap_32k_last_tick + OMAP_32K_TICKS_PER_HZ - now);
+	evt->event_handler(evt);
 
 	return IRQ_HANDLED;
 }
Index: linux-osk/arch/arm/plat-omap/common.c
===================================================================
--- linux-osk.orig/arch/arm/plat-omap/common.c
+++ linux-osk/arch/arm/plat-omap/common.c
@@ -212,7 +212,7 @@ static struct clocksource clocksource_32
 	.read		= omap_32k_read,
 	.mask		= CLOCKSOURCE_MASK(32),
 	.shift		= 10,
-	.is_continuous	= 1,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
 static int __init omap_init_clocksource_32k(void)
Index: linux-osk/kernel/irq/manage.c
===================================================================
--- linux-osk.orig/kernel/irq/manage.c
+++ linux-osk/kernel/irq/manage.c
@@ -593,6 +593,7 @@ static void thread_simple_irq(irq_desc_t
 	unsigned int irq = desc - irq_desc;
 	irqreturn_t action_ret;
 
+	restart:
 	if (action && !desc->depth) {
 		spin_unlock(&desc->lock);
 		action_ret = handle_IRQ_event(irq, action);
@@ -601,6 +602,19 @@ static void thread_simple_irq(irq_desc_t
 		if (!noirqdebug)
 			note_interrupt(irq, desc, action_ret);
 	}
+
+	/*
+	 * Some boards will disable an interrupt when it
+	 * sets IRQ_PENDING . So we have to remove the flag
+	 * and re-enable to handle it.
+	 */
+	if (desc->status & IRQ_PENDING) {
+		desc->status &= ~IRQ_PENDING;
+		if (desc->chip)
+			desc->chip->enable(irq);
+		goto restart;
+	}
+
 	desc->status &= ~IRQ_INPROGRESS;
 }
 
Index: linux-osk/drivers/input/touchscreen/ads7846.c
===================================================================
--- linux-osk.orig/drivers/input/touchscreen/ads7846.c
+++ linux-osk/drivers/input/touchscreen/ads7846.c
@@ -454,7 +454,7 @@ static void ads7846_rx(void *ads)
 			ts->spi->dev.bus_id, ts->tc.ignore, Rt);
 #endif
 		hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
-			      HRTIMER_REL);
+			      HRTIMER_MODE_REL);
 		return;
 	}
 
@@ -473,7 +473,8 @@ static void ads7846_rx(void *ads)
 		ads7846_sync_events(ts);
 	}
 
-	hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD), HRTIMER_REL);
+	hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
+		      HRTIMER_MODE_REL);
 }
 
 static int ads7846_debounce(void *ads, int data_idx, int *val)
@@ -558,7 +559,7 @@ static void ads7846_rx_val(void *ads)
 				status);
 }
 
-static int ads7846_timer(struct hrtimer *handle)
+static enum hrtimer_restart ads7846_timer(struct hrtimer *handle)
 {
 	struct ads7846	*ts = container_of(handle, struct ads7846, timer);
 	int		status = 0;
@@ -609,7 +610,7 @@ static irqreturn_t ads7846_irq(int irq, 
 			disable_irq(ts->spi->irq);
 			ts->pending = 1;
 			hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_DELAY),
-					HRTIMER_REL);
+					HRTIMER_MODE_REL);
 		}
 	}
 	spin_unlock_irqrestore(&ts->lock, flags);
@@ -747,7 +748,7 @@ static int __devinit ads7846_probe(struc
 	ts->input = input_dev;
 	ts->hwmon = hwmon;
 
-	hrtimer_init(&ts->timer, CLOCK_MONOTONIC, HRTIMER_REL);
+	hrtimer_init(&ts->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	ts->timer.function = ads7846_timer;
 
 	spin_lock_init(&ts->lock);
Index: linux-osk/sound/arm/omap/omap-alsa.c
===================================================================
--- linux-osk.orig/sound/arm/omap/omap-alsa.c
+++ linux-osk/sound/arm/omap/omap-alsa.c
@@ -167,7 +167,6 @@ static void audio_stop_dma(struct audio_
 	unsigned long flags;
 	ADEBUG();
 
-	spin_lock_irqsave(&s->dma_lock, flags);
 	s->active = 0;
 	s->period = 0;
 	s->periods = 0;
@@ -176,8 +175,6 @@ static void audio_stop_dma(struct audio_
 	omap_stop_alsa_sound_dma(s);
 
 	omap_clear_alsa_sound_dma(s);
-
-	spin_unlock_irqrestore(&s->dma_lock, flags);
 }
 
 /*

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