ALSA: pcm - Add logging of hwptr updates and interrupt updates

Added the logging functionality to xrun_debug to record the hwptr
updates via snd_pcm_update_hw_ptr() and snd_pcm_update_hwptr_interrupt(),
corresponding to 16 and 8, respectively.

For example,
	# echo 9 > /proc/asound/card0/pcm0p/xrun_debug
will record the position and other parameters at each period interrupt
together with the normal XRUN debugging.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation/sound/alsa/Procfile.txt

@@ -101,6 +101,8 @@ card*/pcm*/xrun_debug
 	  bit 0 = Enable XRUN/jiffies debug messages
 	  bit 1 = Show stack trace at XRUN / jiffies check
 	  bit 2 = Enable additional jiffies check
+	  bit 3 = Log hwptr update at each period interrupt
+	  bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr()
 
 	When the bit 0 is set, the driver will show the messages to
 	kernel log when an xrun is detected.  The debug message is
@@ -117,6 +119,9 @@ card*/pcm*/xrun_debug
 	buggy) hardware that doesn't give smooth pointer updates.
 	This feature is enabled via the bit 2.
 
+	Bits 3 and 4 are for logging the hwptr records.  Note that
+	these will give flood of kernel messages.
+
 card*/pcm*/sub*/info
 	The general information of this PCM sub-stream.
 

sound/core/pcm_lib.c

@@ -233,6 +233,18 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 		xrun(substream);
 		return -EPIPE;
 	}
+	if (xrun_debug(substream, 8)) {
+		char name[16];
+		pcm_debug_name(substream, name, sizeof(name));
+		snd_printd("period_update: %s: pos=0x%x/0x%x/0x%x, "
+			   "hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
+			   name, pos,
+			   (int)runtime->period_size,
+			   (int)runtime->buffer_size,
+			   (long)old_hw_ptr,
+			   (long)runtime->hw_ptr_base,
+			   (long)runtime->hw_ptr_interrupt);
+	}
 	hw_base = runtime->hw_ptr_base;
 	new_hw_ptr = hw_base + pos;
 	hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size;
@@ -353,6 +365,19 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 		xrun(substream);
 		return -EPIPE;
 	}
+	if (xrun_debug(substream, 16)) {
+		char name[16];
+		pcm_debug_name(substream, name, sizeof(name));
+		snd_printd("hw_update: %s: pos=0x%x/0x%x/0x%x, "
+			   "hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
+			   name, pos,
+			   (int)runtime->period_size,
+			   (int)runtime->buffer_size,
+			   (long)old_hw_ptr,
+			   (long)runtime->hw_ptr_base,
+			   (long)runtime->hw_ptr_interrupt);
+	}
+
 	hw_base = runtime->hw_ptr_base;
 	new_hw_ptr = hw_base + pos;