ALSA: hdspm - Constrain periods to 2 on older cards

RME RayDAT and AIO use a fixed buffer size of 16384 samples. With period
sizes of 32-4096, this translates to 4-512 periods.

The older RME cards have a variable buffer size but require exactly two
periods.

This patch enforces nperiods=2 on those cards.
Signed-off-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Cc: <stable@vger.kernel.org> # 2.6.39+
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/rme9652/hdspm.c

@@ -6082,6 +6082,9 @@ static int snd_hdspm_playback_open(struct snd_pcm_substream *substream)
 		snd_pcm_hw_constraint_minmax(runtime,
 					     SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
 					     64, 8192);
+		snd_pcm_hw_constraint_minmax(runtime,
+					     SNDRV_PCM_HW_PARAM_PERIODS,
+					     2, 2);
 		break;
 	}
 
@@ -6156,6 +6159,9 @@ static int snd_hdspm_capture_open(struct snd_pcm_substream *substream)
 		snd_pcm_hw_constraint_minmax(runtime,
 					     SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
 					     64, 8192);
+		snd_pcm_hw_constraint_minmax(runtime,
+					     SNDRV_PCM_HW_PARAM_PERIODS,
+					     2, 2);
 		break;
 	}