ALSA: x86: Allow single period PCM operation

This is an implementation of PCM streaming with only 1 period.
Since the hardware requires the refresh of BDs after each BD
processing finishes, we'd need at least two BDs.  The trick is that
both BDs point to the same content: the address of the PCM buffer
head, and the whole buffer size.  Then it loops over to the whole
buffer again after it finished once.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/x86/intel_hdmi_lpe_audio.h

@@ -31,7 +31,7 @@
 #define HAD_MAX_BUFFER		((1024 * 1024 - 1) & ~0x3f)
 #define HAD_DEFAULT_BUFFER	(600 * 1024) /* default prealloc size */
 #define HAD_MAX_PERIODS		256	/* arbitrary, but should suffice */
-#define HAD_MIN_PERIODS		2
+#define HAD_MIN_PERIODS		1
 #define HAD_MAX_PERIOD_BYTES	((HAD_MAX_BUFFER / HAD_MIN_PERIODS) & ~0x3f)
 #define HAD_MIN_PERIOD_BYTES	1024	/* might be smaller */
 #define HAD_FIFO_SIZE		0 /* fifo not being used */