ALSA: hda - Add position_fix=4 (COMBO) option

This patch adds a new position_fix option value, 4, as a combo mode
to use LPIB for playbacks and POSBUF for captures.  It's the way
recommended by Intel hardware guys.

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

Documentation/sound/alsa/ALSA-Configuration.txt

@@ -860,7 +860,8 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
 
     [Multiple options for each card instance]
     model	- force the model name
-    position_fix - Fix DMA pointer (0 = auto, 1 = use LPIB, 2 = POSBUF)
+    position_fix - Fix DMA pointer (0 = auto, 1 = use LPIB, 2 = POSBUF,
+    		   3 = VIACOMBO, 4 = COMBO)
     probe_mask  - Bitmask to probe codecs (default = -1, meaning all slots)
     		  When the bit 8 (0x100) is set, the lower 8 bits are used
 		  as the "fixed" codec slots; i.e. the driver probes the
@@ -925,6 +926,11 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
 	    (Usually SD_LPIB register is more accurate than the
 	    position buffer.)
 
+	    position_fix=3 is specific to VIA devices.  The position
+	    of the capture stream is checked from both LPIB and POSBUF
+	    values.  position_fix=4 is a combination mode, using LPIB
+	    for playback and POSBUF for capture.
+
     NB: If you get many "azx_get_response timeout" messages at
     loading, it's likely a problem of interrupts (e.g. ACPI irq
     routing).  Try to boot with options like "pci=noacpi".  Also, you

Documentation/sound/alsa/HD-Audio.txt

@@ -59,7 +59,12 @@ a case, you can change the default method via `position_fix` option.
 `position_fix=1` means to use LPIB method explicitly.
 `position_fix=2` means to use the position-buffer.
 `position_fix=3` means to use a combination of both methods, needed
-for some VIA and ATI controllers.  0 is the default value for all other
+for some VIA controllers.  The capture stream position is corrected
+by comparing both LPIB and position-buffer values.
+`position_fix=4` is another combination available for all controllers,
+and uses LPIB for the playback and the position-buffer for the capture
+streams.
+0 is the default value for all other
 controllers, the automatic check and fallback to LPIB as described in
 the above.  If you get a problem of repeated sounds, this option might
 help.