Re: Maintaining sound card at a specific frequency

[Takashi Iwai <tiwai@suse.de>]

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At Tue, 18 Jan 2005 18:08:50 +0100,
I wrote:
> 
> If this works like you want, only the locking is missing...

The attached is an experimental patch to add this feature.
You can lock system clock via

	amixer cset iface=PCM,name="System Clock Source Locking" on

It's untested, as usual.


Takashi

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Index: alsa-kernel/pci/rme9652/hdsp.c
===================================================================
RCS file: /suse/tiwai/cvs/alsa/alsa-kernel/pci/rme9652/hdsp.c,v
retrieving revision 1.81
diff -u -r1.81 hdsp.c
--- alsa-kernel/pci/rme9652/hdsp.c	14 Jan 2005 19:50:48 -0000	1.81
+++ alsa-kernel/pci/rme9652/hdsp.c	18 Jan 2005 17:44:54 -0000
@@ -450,6 +450,7 @@
 	u32                   control2_register;     /* cached value */
 	u32                   creg_spdif;
 	u32                   creg_spdif_stream;
+	int                   clock_source_locked;
 	char                 *card_name;	     /* digiface/multiface */
 	HDSP_IO_Type          io_type;               /* ditto, but for code use */
         unsigned short        firmware_rev;
@@ -2159,7 +2160,7 @@
 	    if (val > 6) val = 6;
 	}
 	spin_lock_irq(&hdsp->lock);
-	if (val != hdsp_clock_source(hdsp)) {
+	if (val != hdsp_clock_source(hdsp) && ! hdsp->clock_source_locked) {
 		change = (hdsp_set_clock_source(hdsp, val) == 0) ? 1 : 0;
 	} else {
 		change = 0;
@@ -2168,6 +2169,34 @@
 	return change;
 }
 
+static int snd_hdsp_info_clock_source_lock(snd_kcontrol_t *kcontrol, snd_ctl_elem_info_t * uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+	uinfo->count = 1;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = 1;
+	return 0;
+}
+
+static int snd_hdsp_get_clock_source_lock(snd_kcontrol_t * kcontrol, snd_ctl_elem_value_t * ucontrol)
+{
+	hdsp_t *hdsp = snd_kcontrol_chip(kcontrol);
+	
+	ucontrol->value.integer.value[0] = hdsp->clock_source_locked;
+	return 0;
+}
+
+static int snd_hdsp_put_clock_source_lock(snd_kcontrol_t * kcontrol, snd_ctl_elem_value_t * ucontrol)
+{
+	hdsp_t *hdsp = snd_kcontrol_chip(kcontrol);
+	int change;
+
+	change = (int)ucontrol->value.integer.value[0] != hdsp->clock_source_locked;
+	if (change)
+		hdsp->clock_source_locked = ucontrol->value.integer.value[0];
+	return change;
+}
+
 #define HDSP_DA_GAIN(xname, xindex) \
 { .iface = SNDRV_CTL_ELEM_IFACE_HWDEP, \
   .name = xname, \
@@ -3129,6 +3158,13 @@
 HDSP_SPDIF_NON_AUDIO("IEC958 Non-audio Bit", 0),
 /* 'Sample Clock Source' complies with the alsa control naming scheme */ 
 HDSP_CLOCK_SOURCE("Sample Clock Source", 0),
+{
+	.iface = SNDRV_CTL_ELEM_IFACE_PCM,
+	.name = "Sample Clock Source Locking",
+	.info = snd_hdsp_info_clock_source_lock,
+	.get = snd_hdsp_get_clock_source_lock,
+	.put = snd_hdsp_put_clock_source_lock,
+},
 HDSP_SYSTEM_CLOCK_MODE("System Clock Mode", 0),
 HDSP_PREF_SYNC_REF("Preferred Sync Reference", 0),
 HDSP_AUTOSYNC_REF("AutoSync Reference", 0),
@@ -3360,6 +3396,7 @@
 	snd_iprintf (buffer, "System Clock Mode: %s\n", system_clock_mode);
 
 	snd_iprintf (buffer, "System Clock Frequency: %d\n", hdsp->system_sample_rate);
+	snd_iprintf (buffer, "System Clock Locked: %s\n", hdsp->clock_source_locked ? "Yes" : "No");
 		
 	snd_iprintf(buffer, "\n");
 
@@ -3882,21 +3919,19 @@
 		spin_unlock_irq(&hdsp->lock);
  		return 0;
 
-	} else {
-		spin_unlock_irq(&hdsp->lock);
 	}
 
 	/* how to make sure that the rate matches an externally-set one ?
 	 */
 
-	spin_lock_irq(&hdsp->lock);
-	if ((err = hdsp_set_rate(hdsp, params_rate(params), 0)) < 0) {
-		spin_unlock_irq(&hdsp->lock);
-		_snd_pcm_hw_param_setempty(params, SNDRV_PCM_HW_PARAM_RATE);
-		return err;
-	} else {
-		spin_unlock_irq(&hdsp->lock);
+	if (! hdsp->clock_source_locked) {
+		if ((err = hdsp_set_rate(hdsp, params_rate(params), 0)) < 0) {
+			spin_unlock_irq(&hdsp->lock);
+			_snd_pcm_hw_param_setempty(params, SNDRV_PCM_HW_PARAM_RATE);
+			return err;
+		}
 	}
+	spin_unlock_irq(&hdsp->lock);
 
 	if ((err = hdsp_set_interrupt_interval(hdsp, params_period_size(params))) < 0) {
 		_snd_pcm_hw_param_setempty(params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
@@ -4318,13 +4353,17 @@
 
 	snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
 	snd_pcm_hw_constraint_list(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, &hdsp_hw_constraints_period_sizes);
-	if (hdsp->io_type == H9632) {
-		runtime->hw.channels_min = hdsp->qs_out_channels;
-		runtime->hw.channels_max = hdsp->ss_out_channels;
+	if (hdsp->clock_source_locked) {
+		runtime->hw.rate_min = runtime->hw.rate_max = hdsp->system_sample_rate;
+	} else if (hdsp->io_type == H9632) {
 		runtime->hw.rate_max = 192000;
 		runtime->hw.rates = SNDRV_PCM_RATE_KNOT;
 		snd_pcm_hw_constraint_list(runtime, 0, SNDRV_PCM_HW_PARAM_RATE, &hdsp_hw_constraints_9632_sample_rates);
 	}
+	if (hdsp->io_type == H9632) {
+		runtime->hw.channels_min = hdsp->qs_out_channels;
+		runtime->hw.channels_max = hdsp->ss_out_channels;
+	}	
 	
 	snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
 			     snd_hdsp_hw_rule_out_channels, hdsp,