ALSA in 2.6.14: RTC timer breaks MIDI

ALSA in 2.6.14: RTC timer breaks MIDI

[Marek Szuba]

(I'm having problems with access to the ALSA bug tracker, that's why I'm 
reporting this issue here)

Hello everyone,

A couple of days ago I tried to play a MIDI file on a 2.6.14 box with 
emu10k1 for sound (Audigy 2 ZS) and was surprised to hear that the 
sequencer no longer works - or to be exact, when having it play any MIDI 
song it only starts playing the first note in each channel and leaves them 
like that, playing the same tones until the player's closed. Going back to 
2.6.13 made the problem go away; on the other hand, even an upgrade of 
ALSA userspace components to the latest version doesn't help with 2.6.14.

Having investigated a bit, I found out the problem lies with the 
newly-added "Use RTC as default sequence timer" option; turning it off and 
recompiling the kernel lets MIDI be played as before.

By the way, shouldn't snd-rtctimer be automatically pulled in if the 
aforementioned option is set and MIDI drivers are loaded? I have noticed 
the only way to make it actually be used by other ALSA modules is to have 
it manually loaded before all the others, as it doesn't get loaded on its 
own and loading it after the others doesn't cause it to be used, at least 
not automatically. Of course regardless of whether and how this module is 
loaded doesn't affect the fact that as long as the aforementioned option 
is set, MIDI remains useless; recompilation is the only way.

PS. In case it is not clear, in the setup in question all ALSA components 
are built as modules.

Let me know if you need more information.

Regards,
-- 
MS

Re: ALSA in 2.6.14: RTC timer breaks MIDI

[Takashi Iwai]

At Thu, 10 Nov 2005 17:48:04 +0100 (CET),
Marek Szuba wrote:
> 
> (I'm having problems with access to the ALSA bug tracker, that's why I'm 
> reporting this issue here)
> 
> Hello everyone,
> 
> A couple of days ago I tried to play a MIDI file on a 2.6.14 box with 
> emu10k1 for sound (Audigy 2 ZS) and was surprised to hear that the 
> sequencer no longer works - or to be exact, when having it play any MIDI 
> song it only starts playing the first note in each channel and leaves them 
> like that, playing the same tones until the player's closed. Going back to 
> 2.6.13 made the problem go away; on the other hand, even an upgrade of 
> ALSA userspace components to the latest version doesn't help with 2.6.14.

A known problem.  Try the patch below.


Takashi

---
diff --git a/drivers/char/rtc.c b/drivers/char/rtc.c
--- a/drivers/char/rtc.c
+++ b/drivers/char/rtc.c
@@ -149,8 +149,22 @@ static void get_rtc_alm_time (struct rtc
 #ifdef RTC_IRQ
 static void rtc_dropped_irq(unsigned long data);
 
-static void set_rtc_irq_bit(unsigned char bit);
-static void mask_rtc_irq_bit(unsigned char bit);
+static void set_rtc_irq_bit_locked(unsigned char bit);
+static void mask_rtc_irq_bit_locked(unsigned char bit);
+
+static inline void set_rtc_irq_bit(unsigned char bit)
+{
+	spin_lock_irq(&rtc_lock);
+	set_rtc_irq_bit_locked(bit);
+	spin_unlock_irq(&rtc_lock);
+}
+
+static void mask_rtc_irq_bit(unsigned char bit)
+{
+	spin_lock_irq(&rtc_lock);
+	mask_rtc_irq_bit_locked(bit);
+	spin_unlock_irq(&rtc_lock);
+}
 #endif
 
 static int rtc_proc_open(struct inode *inode, struct file *file);
@@ -401,18 +415,19 @@ static int rtc_do_ioctl(unsigned int cmd
 	}
 	case RTC_PIE_OFF:	/* Mask periodic int. enab. bit	*/
 	{
-		mask_rtc_irq_bit(RTC_PIE);
+		unsigned long flags; /* can be called from isr via rtc_control() */
+		spin_lock_irqsave (&rtc_lock, flags);
+		mask_rtc_irq_bit_locked(RTC_PIE);
 		if (rtc_status & RTC_TIMER_ON) {
-			spin_lock_irq (&rtc_lock);
 			rtc_status &= ~RTC_TIMER_ON;
 			del_timer(&rtc_irq_timer);
-			spin_unlock_irq (&rtc_lock);
 		}
+		spin_unlock_irqrestore (&rtc_lock, flags);
 		return 0;
 	}
 	case RTC_PIE_ON:	/* Allow periodic ints		*/
 	{
-
+		unsigned long flags; /* can be called from isr via rtc_control() */
 		/*
 		 * We don't really want Joe User enabling more
 		 * than 64Hz of interrupts on a multi-user machine.
@@ -421,14 +436,14 @@ static int rtc_do_ioctl(unsigned int cmd
 			(!capable(CAP_SYS_RESOURCE)))
 			return -EACCES;
 
+		spin_lock_irqsave (&rtc_lock, flags);
 		if (!(rtc_status & RTC_TIMER_ON)) {
-			spin_lock_irq (&rtc_lock);
 			rtc_irq_timer.expires = jiffies + HZ/rtc_freq + 2*HZ/100;
 			add_timer(&rtc_irq_timer);
 			rtc_status |= RTC_TIMER_ON;
-			spin_unlock_irq (&rtc_lock);
 		}
-		set_rtc_irq_bit(RTC_PIE);
+		set_rtc_irq_bit_locked(RTC_PIE);
+		spin_unlock_irqrestore (&rtc_lock, flags);
 		return 0;
 	}
 	case RTC_UIE_OFF:	/* Mask ints from RTC updates.	*/
@@ -609,6 +624,7 @@ static int rtc_do_ioctl(unsigned int cmd
 	{
 		int tmp = 0;
 		unsigned char val;
+		unsigned long flags; /* can be called from isr via rtc_control() */
 
 		/* 
 		 * The max we can do is 8192Hz.
@@ -631,9 +647,9 @@ static int rtc_do_ioctl(unsigned int cmd
 		if (arg != (1<<tmp))
 			return -EINVAL;
 
-		spin_lock_irq(&rtc_lock);
+		spin_lock_irqsave(&rtc_lock, flags);
 		if (hpet_set_periodic_freq(arg)) {
-			spin_unlock_irq(&rtc_lock);
+			spin_unlock_irqrestore(&rtc_lock, flags);
 			return 0;
 		}
 		rtc_freq = arg;
@@ -641,7 +657,7 @@ static int rtc_do_ioctl(unsigned int cmd
 		val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
 		val |= (16 - tmp);
 		CMOS_WRITE(val, RTC_FREQ_SELECT);
-		spin_unlock_irq(&rtc_lock);
+		spin_unlock_irqrestore(&rtc_lock, flags);
 		return 0;
 	}
 #endif
@@ -844,12 +860,15 @@ int rtc_control(rtc_task_t *task, unsign
 #ifndef RTC_IRQ
 	return -EIO;
 #else
-	spin_lock_irq(&rtc_task_lock);
+	unsigned long flags;
+	if (cmd != RTC_PIE_ON && cmd != RTC_PIE_OFF && cmd != RTC_IRQP_SET)
+		return -EINVAL;
+	spin_lock_irqsave(&rtc_task_lock, flags);
 	if (rtc_callback != task) {
-		spin_unlock_irq(&rtc_task_lock);
+		spin_unlock_irqrestore(&rtc_task_lock, flags);
 		return -ENXIO;
 	}
-	spin_unlock_irq(&rtc_task_lock);
+	spin_unlock_irqrestore(&rtc_task_lock, flags);
 	return rtc_do_ioctl(cmd, arg, 1);
 #endif
 }
@@ -1306,40 +1325,32 @@ static void get_rtc_alm_time(struct rtc_
  * meddles with the interrupt enable/disable bits.
  */
 
-static void mask_rtc_irq_bit(unsigned char bit)
+static void mask_rtc_irq_bit_locked(unsigned char bit)
 {
 	unsigned char val;
 
-	spin_lock_irq(&rtc_lock);
-	if (hpet_mask_rtc_irq_bit(bit)) {
-		spin_unlock_irq(&rtc_lock);
+	if (hpet_mask_rtc_irq_bit(bit))
 		return;
-	}
 	val = CMOS_READ(RTC_CONTROL);
 	val &=  ~bit;
 	CMOS_WRITE(val, RTC_CONTROL);
 	CMOS_READ(RTC_INTR_FLAGS);
 
 	rtc_irq_data = 0;
-	spin_unlock_irq(&rtc_lock);
 }
 
-static void set_rtc_irq_bit(unsigned char bit)
+static void set_rtc_irq_bit_locked(unsigned char bit)
 {
 	unsigned char val;
 
-	spin_lock_irq(&rtc_lock);
-	if (hpet_set_rtc_irq_bit(bit)) {
-		spin_unlock_irq(&rtc_lock);
+	if (hpet_set_rtc_irq_bit(bit))
 		return;
-	}
 	val = CMOS_READ(RTC_CONTROL);
 	val |= bit;
 	CMOS_WRITE(val, RTC_CONTROL);
 	CMOS_READ(RTC_INTR_FLAGS);
 
 	rtc_irq_data = 0;
-	spin_unlock_irq(&rtc_lock);
 }
 #endif
 

Re: ALSA in 2.6.14: RTC timer breaks MIDI

[Marek Szuba]

On Fri, 11 Nov 2005, Takashi Iwai wrote:

> A known problem.  Try the patch below.
Works like a charm now, thanks.

-- 
MS

Re: ALSA in 2.6.14: RTC timer breaks MIDI

[Lee Revell]

On Sat, 2005-11-12 at 04:07 +0100, Marek Szuba wrote:
> On Fri, 11 Nov 2005, Takashi Iwai wrote:
> 
> > A known problem.  Try the patch below.
> Works like a charm now, thanks.
> 

tiwai, can you forward the patch to stable@kernel.org?  This really
needs to make it into 2.6.14.3.

Lee

Re: ALSA in 2.6.14: RTC timer breaks MIDI

[Takashi Iwai]

At Fri, 11 Nov 2005 22:17:03 -0500,
Lee Revell wrote:
> 
> On Sat, 2005-11-12 at 04:07 +0100, Marek Szuba wrote:
> > On Fri, 11 Nov 2005, Takashi Iwai wrote:
> > 
> > > A known problem.  Try the patch below.
> > Works like a charm now, thanks.
> > 
> 
> tiwai, can you forward the patch to stable@kernel.org?  This really
> needs to make it into 2.6.14.3.

Yep, already submitted.


Takashi