[ALSA] buffersize and constraints on pmac

PPC PMAC driver
Buffersize is a bit small compared to the OSS driver (dmasound.h says
128kb is limit for Amiga, for pmac 256kb is used)
At least on Snapper, some samplerates cause choppy sound when
periods<3 or buffersize is not a multiple of periodsize.
Signed-off-by: Danny Tholen <obiwan@mailmij.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/ppc/pmac.c

@@ -425,10 +425,10 @@ static snd_pcm_hardware_t snd_pmac_playback =
 	.rate_max =		44100,
 	.channels_min =		2,
 	.channels_max =		2,
-	.buffer_bytes_max =	32768,
+	.buffer_bytes_max =	131072,
 	.period_bytes_min =	256,
 	.period_bytes_max =	16384,
-	.periods_min =		1,
+	.periods_min =		3,
 	.periods_max =		PMAC_MAX_FRAGS,
 };
 
@@ -444,10 +444,10 @@ static snd_pcm_hardware_t snd_pmac_capture =
 	.rate_max =		44100,
 	.channels_min =		2,
 	.channels_max =		2,
-	.buffer_bytes_max =	32768,
+	.buffer_bytes_max =	131072,
 	.period_bytes_min =	256,
 	.period_bytes_max =	16384,
-	.periods_min =		1,
+	.periods_min =		3,
 	.periods_max =		PMAC_MAX_FRAGS,
 };
 
@@ -550,6 +550,8 @@ static int snd_pmac_pcm_open(pmac_t *chip, pmac_stream_t *rec, snd_pcm_substream
 	if (chip->can_duplex)
 		snd_pcm_set_sync(subs);
 
+	/* constraints to fix choppy sound */
+	snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
 	return 0;
 }